FILM FORMAT
A film format is a technical definition of a set of standard characteristics regarding image capture on photographic film, for either stills or movies. It can also apply to projected film, either slides or movies. The primary characteristic of a film format is its size and shape.
In the case of motion picture film, the format may also include audio parameters (though often not). Other characteristics usually include the film gauge, pulldown method, lens anamorphosis (or lack thereof), and film gate or projector aperture dimensions, all of which need to be defined for photography as well as projection, as they may differ.
(A) Type Introduced Discontinued Size Detailed article Comment
101 roll film 1895 1956 3½" × 3½"
102 roll film 1896 1933 1½" × 2"
103 roll film 1896 1949 3¾" × 4¾"
104 roll film 1897 1949 4¾" × 3¾"
105 roll film 1897 1949 2¼" × 3¼" 120 film
106 for roll holder 1898 1924 3½" × 3½"
107 for roll holder 1898 1924 3¼" × 4¼"
108 for roll holder 1898 1929 4¼" × 3¼"
109 for roll holder 1898 1924 4" × 5"
110 (early roll film) for roll holder 1898 1929 5" × 4" 110 film (roll format) No relation to the later 110 cartridge format for "pocket" cameras.
110 ("Pocket Instamatic") cartridge 1972 Present 13 × 17 mm 110 film Introduced with Kodak's "Pocket Instamatic" series
111 for roll holder 1898 Unknown 6½" × 4¾"
112 for roll holder 1898 1924 7" × 5"
113 for roll holder 1898 Unknown 9 × 12 cm
114 for roll holder 1898 Unknown 12 × 9 cm
115 roll film 1898 1949 6¾" × 4¾"
116 roll film 1899 1984 2½" × 4
117 roll film 1900 1949 2¼" × 2¼" 120 film
118 roll film 1900 1961 3¼" × 4¼"
119 roll film 1900 1940 4¼" × 3¼"
120 roll film 1901 Present 120 film
121 roll film 1902 1941 1⅝" × 2½"
122 roll film 1903 1971 3¼" × 5½", Postcard
123 roll film 1904 1949 4" × 5"
124 roll film 1905 1961 3¼" × 4¼"
125 roll film 1905 1949 3¼" × 5½"
126 (early roll film) roll film 1906 1949 4¼" × 6½" 126 film (roll format) No relation to the 126 cartridge format introduced in 1963.
126 ("Instamatic") cartridge 1963 1999(B) 26.5 × 26.5 mm 126 film Introduced with first "Instamatic" cameras under the name "Kodapak"
127 roll film 1912 1995(C) 4 × 4 cm 127 film
128 roll film 1912 1941 1½" × 2¼"
129 roll film 1912 1951 1⅞" × 3"
130 roll film 1916 1961 2⅞" × 4⅞"
135 cartridge 1934 Present 135 film
220 roll film 1965 Present 120 film
235 loading spool 1934 Unknown 24 × 36 mm 135 film 35mm film in daylight-loading spool
240 / APS cartridge 1996 Present Advanced Photo System
335 stereo pairs 1952 Unknown 24 × 24 mm 135 film For stereo pairs
435 loading spool 1934 Unknown 24 × 36 mm 135 film 35mm film in daylight-loading spool
616 roll film 1931 1984 2½" × 4¼" or 2½" × 2⅛" 616 film
620 roll film 1931 1995 120 film
645 format only 6 × 4.5 cm 120 film
828 roll film 1935 1985 28 × 40 mm, 35 mm wide Bantam, 8 exp 828 film
35 roll film 1916 1933 1¼" × 1¾", 35 mm wide
Disc cassette 1982 1998 Disc film
Minox roll film 1938 Present 8 × 11 mm, nominally 9.5 mm wide (in reality 9.2-9.3mm), 15, 36 or 50 exp.
Karat cartridge 1936 1963 Early AGFA cartridge for 35 mm film
Rapid cartridge 1964 1990s AGFA cartridge for 35 mm film, 12 exp (replaced Karat, same system)
SL cartridge 1958 1990 Orwo Schnell-Lade Kassette for 35 mm film
K 16 cartridge 1987 Unknown Orwo, 16 mm wide, 20 exp
FILM SPEED
Film speed is the measure of a photographic film's sensitivity to light. Film with lower sensitivity (lower ISO speed) requires a longer exposure and is thus called a slow film, while stock with higher sensitivity (higher ISO speed) can shoot the same scene with a shorter exposure and is called a fast film.
In the first approximation the amount of light energy which reaches the film determines the effect on the emulsion, so that if the brightness of the light is multiplied by a factor and the exposure of the film decreased by the same factor so that the energy received is the same, the film will be exposed to the same density; this rule is called reciprocity, and the concept of a unique speed for an emulsion is possible because reciprocity holds. In practice this holds reasonably well for normal photographic films for the range of exposures usually used, say 1/1000 sec to 1 sec, but longer exposures, different for different films, are required outside these limits, a phenomenon known as reciprocity failure.
ISO film speed scales
International standard ISO 5800:1987 from the International Organization for Standardization (ISO) defines both an arithmetic scale and a logarithmic scale for measuring color-negative film speed. Related standards ISO 6:1993 and ISO 2240:2003 define scales for speeds of black-and-white negative film and color reversal film.
In the ISO arithmetic scale, which corresponds to the older ASA scale, doubling the speed of a film (that is, halving the amount of light that is necessary to expose the film) implies doubling the numeric value that designates the film speed. In the ISO logarithmic scale, which corresponds to the older DIN scale, doubling the speed of a film implies adding 3° to the numeric value that designates the film speed. For example, a film rated ISO 200/24° is twice as sensitive as a film rated ISO 100/21°.
Commonly, the logarithmic speed is omitted, and only the arithmetic speed is given (e.g., “ISO 100”). In such cases, the quoted “ISO” speed is essentially the same as the older “ASA” speed.
GOST (Russian: ГОСТ) is a pre-1987 arithmetic standard used in the former Eastern Bloc. It was almost, but not quite identical to the ASA standard. After 1987 the GOST scale was aligned to the ISO scale. GOST markings are only found on pre-1987 photographic equipment (film, cameras, lightmeters, etc.) of Eastern Bloc manufacture.
The most common ISO film speeds are 25/15°, 50/18°, 100/21°, 200/24°, 400/27°, 800/30°, 1600/33°, and 3200/36°. Consumer film speeds are generally between 100/21° and 800/30°, inclusive.
Conversion from the logarithmic speed S° to the arithmetic speed S is given by[1]
S = 10^{\left( {S^\circ - 1} \right)/10}
and rounding to the nearest standard arithmetic speed in the table below. By simple rearrangement, conversion from arithmetic speed to logarithmic speed is given by
S^\circ = 10 \log S + 1
and rounding to the nearest integer.
The following table shows the correspondence among the various speed scales:
ISO arithmetic scale
(old ASA scale) ISO log scale
(old DIN scale) GOST
(Soviet pre-1987) Example of film stock
with this nominal speed
6 9° original Kodachrome
8 10°
10 11° Kodachrome 8 mm film
12 12° 11 Gevacolor 8 mm reversal film
16 13° 11 Agfacolor 8 mm reversal film
20 14° 16 Adox CMS 20
25 15° 22 old Agfacolor, Kodachrome 25
32 16° 22 Kodak Panatomic-X
40 17° 32 Kodachrome 40 (movie)
50 18° 45 Fuji RVP (Velvia)
64 19° 45 Kodachrome 64, Ektachrome-X
80 20° 65 Ilford Commercial Ortho
100 21° 90 Kodacolor Gold, Kodak T-Max (TMX)
125 22° 90 Ilford FP4, Kodak Plus-X Pan
160 23° 130 Fuji Pro 160C/S, Kodak High-Speed Ektachrome
200 24° 180 Fujicolor Superia 200
250 25° 180
320 26° 250 Kodak Tri-X Pan Professional (TXP)
400 27° 350 Kodak T-Max (TMY), Tri-X 400, Ilford HP5
500 28° 350
640 29° 560 Polaroid 600
800 30° 700 Fuji Pro 800Z
1000 31° 700 Ilford Delta 3200 (see text below)
1250 32°
1600 33° 1400–1440 Fujicolor 1600
2000 34°
2500 35°
3200 36° 2800–2880 Kodak P3200 TMAX
4000 37°
5000 38°
6400 39°
[edit] Determining film speed
Method of determining speed for black-and-white film.
Method of determining speed for black-and-white film.
Film speed is found from a plot of optical density vs. log of exposure for the film, known as the D–log H curve or Hurter–Driffield curve. There typically are five regions in the curve: the base + fog, the toe, the linear region, the shoulder, and the overexposed region. For black and white negative film, the “speed point” m is the point on the curve where density exceeds the base + fog density by 0.1 when the negative is developed so that a point n where the log of exposure is 1.3 units greater than the exposure at point m has a density 0.8 greater than the density at point m. The exposure Hm, in lux-s, is that for point m when the specified contrast condition is satisfied. The ISO arithmetic speed then is
S = \frac {0.8} {H_\mathrm{m}} .
Determining speed for color negative film is similar in concept but more complex because it involves separate curves for blue, green, and red. The film is processed according to the film manufacturer’s recommendations rather than to a specified contrast. ISO speed for color reversal film is determined from the middle rather than the threshold of the curve; it again involves separate curves for blue, green, and red, and the film is processed according to the film manufacturer’s recommendations.
[edit] Applying film speed
Film speed is used in the exposure equations to find the appropriate exposure parameters. Four variables are available to the photographer to obtain the desired effect: lighting, film speed, f-number (aperture size), and shutter speed (exposure time). The equation may be expressed as ratios, or, by taking the logarithm (base 2) of both sides, by addition, using the APEX system, in which every increment of 1 is a doubling of exposure, known as a "stop". The effective f-number is proportional to the ratio between the lens focal length and aperture diameter, which is proportional to the square root of the aperture area. Thus, a lens set to f/1.4 allows twice as much light to strike the focal plane as a lens set to f/2. Therefore, each f-number factor of the square root of two (approximately 1.4) is also a stop, so lenses are typically marked in that progression: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc.
[edit] Exposure index
Exposure index, or EI, refers to speed rating assigned to a particular film and shooting situation, and used in the exposure meter or equation, to compensate for equipment calibration inaccuracies or process variables, or to achieve certain effects. Exposure index may or may not be the same as manufacturer's film speed rating for that particular film.
The exposure index is sometimes called the speed setting, as opposed to the speed rating.
For example, a photographer may choose to rate a 400 ISO speed film at 800 and then use push processing in order to get printable negatives from low-light conditions. In this case it is said that film has been shot at EI 800.
Another example of a situation when exposure index would differ from film manufacturer's rating is when a camera shutter is known to be miscalibrated and consistently overexposes or underexposes the film; similarly, a light meter can be known to understate or overstate lighting conditions. In such cases one could adjust EI rating accordingly in order to compensate for these effects and consistently produce correctly exposed negatives.
[edit] Film grain
Main article: Film grain
Grainy high speed B/W film negative
Grainy high speed B/W film negative
Film speed is roughly related to granularity, the size of the grains of silver halide in the emulsion, since larger grains give film a greater sensitivity to light. Fine-grain stock, such as portrait film or those used for the intermediate stages of copying original camera negatives, is "slow", meaning that the amount of light used to expose it must be high or the shutter must be open longer. Fast films, used for shooting in poor light or for shooting fast motion, produce a grainier image. Each grain of silver halide develops in an all-or-nothing way into dark silver or nothing. Thus, each grain is a threshold detector; in aggregate, their effect can be thought of as a noisy nonlinear analog light detector.
Kodak has defined a "Print Grain Index" (PGI) to characterize film grain (color negative films only), based on perceptual just noticeable difference of graininess in prints. They also define "granularity", a measurement of grain using an RMS measurement of density fluctuations in uniformly-exposed film, measured with a microdensitometer with 48 micrometre aperture.[2] Granularity varies with exposure — underexposed film looks grainier than overexposed film.
[edit] Improvements in film
In the early 1980s, there were some radical improvements in film stock. It became possible to shoot color film in very low light and produce a fine-grained image with a good range of midtones.[citation needed]
[edit] Use of grain
In advertising, music videos, and some drama, mismatches of grain, color cast, and so forth between shots are often deliberate and added in post-production.
[edit] Altering film speed
Certain high-speed black-and-white films, such as Ilford Delta 3200 and Kodak T-Max P3200 (TMZ), are marketed with higher speeds on the box than their true ISO speed (determined using the ISO testing methodology). For example, the Ilford product is actually an ISO 1000 film, according to its data sheet (PDF). The manufacturers are careful not to refer to the 3200 number as an ISO speed on the packaging. These films can be successfully exposed at EI 3200 (or any of several other speeds) through the use of push processing. The most sensitive sensor common in commercial photography may be the Silicon Intensified Target vidicon, at ASA 200,000, used in TV cameras.
[edit] Digital camera ISO speed and exposure index
A CCD image sensor, 2/3 inch size.
A CCD image sensor, 2/3 inch size.
In digital camera systems, an arbitrary relationship between exposure and finished image lightness can be achieved by setting the system's signal gain. This gain is not exactly the same as a sensitivity, which is why the relationship to an ISO speed is more complicated. On a camera, however, setting an ISO speed and setting the exposure accordingly, whether automatically or manually with the help of an exposure meter, should result in a photo of appropriate lightness just as with film cameras.
For digital photo cameras ("digital still cameras"), the ISO standard 12232:2006[3] specifies several definitions of the speed rating depending on the sensor sensitivity, the sensor noise, and the appearance of the resulting image. The digital ISO speed ratings are related to the conventional film-speed ratings in how a standard 18 percent reflective surface would appear in an image under given lighting conditions.
ISO speed ratings of a digital camera are based on the properties of the sensor and the image processing done in the camera, and are expressed in terms of the luminous exposure H (in lux seconds) arriving at the sensor. For a typical camera lens with an effective focal length f that is much smaller than the distance between the camera and the photographed scene, H is given by
H = \frac{q L t}{N^2},
where L is the luminance of the scene (in candela per m², t is the exposure time (in seconds), N is the aperture f-number, and
q = \frac{\pi}{4} T\, v(\theta)\, \cos^4\theta
is a factor depending on the transmittance T of the lens, the vignetting factor v(θ), and the angle θ relative to the axis of the lens. A typical value is q = 0.65, based on θ = 10°, T = 0.9, and v = 0.98.
The saturation-based speed is defined as
S_{\mathrm{sat}} = \frac{78}{H_{\mathrm{sat}}},
where Hsat is the maximum possible exposure that does not lead to a clipped or bloomed camera output. Typically, the lower limit of the saturation speed is determined by the sensor itself, but with the gain of the amplifier between the sensor and the A/D-converter, the saturation speed can be increased. The factor 78 is chosen such that exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. The factor √2 indicates that there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface.
The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels. Two ratios are used, the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio. These ratios have been subjectively determined based on a resolution of 70 pixels per cm (180 DPI) when viewed at 25 cm (10 inch) distance. The signal-to-noise ratio is defined as the standard deviation of a weighted average of the luminance (overall brightness) and color of individual pixels. The noise-based speed is mostly determined by the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter.
In addition to the above speed ratings, the standard also defines the standard output sensitivity (SOS), how the exposure is related to the digital pixel values in the output image. It is defined as
S_{\mathrm{sos}} = \frac{10}{H_{\mathrm{sos}}},
where Hsos is the exposure that will lead to values of 118 in 8-bit pixels, which is 18 percent of the saturation value in images encoded as sRGB or with gamma = 2.2.
The standard specifies how speed ratings should be reported by the camera. If the noise-based speed (40:1) is higher than the saturation-based speed, the noise-based speed should be reported, rounded downwards to a standard value (e.g. 200, 250, 320, or 400). The rationale is that exposure according to the lower saturation-based speed would not result in a visibly better image. In addition, an exposure latitude can be specified, ranging from the saturation-based speed to the 10:1 noise-based speed. If the noise-based speed (40:1) is lower than the saturation-based speed, or undefined because of high noise, the saturation-based speed is specified, rounded upwards to a standard value, because using the noise-based speed would lead to overexposed images. The camera may also report the SOS-based speed (explicitly as being an SOS speed), rounded to the nearest standard speed rating.
For example, a camera sensor may have the following properties: S40:1 = 107, S10:1 = 1688, and Ssat = 49. According to the standard, the camera should report its sensitivity as
ISO 100 (daylight)
ISO speed latitude 50–1600
ISO 100 (SOS, daylight).
The SOS rating could be user controlled. For a different camera with a noisier sensor, the properties might be S40:1 = 40, S10:1 = 800, and Ssat = 200. In this case, the camera should report
ISO 200 (daylight),
as well as a user-adjustable SOS value. In all cases, the camera should indicate for the white balance setting for which the speed rating applies, such as daylight or tungsten (incandescent light).
Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user "ISO" setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes.
As should be clear from the above, a greater SOS setting for a given sensor comes with some loss of image quality, just like with analog film. However, this loss is visible as image noise rather than grain. The best digital cameras as of 2008 exhibit no perceptible noise at ISO 200 sensitivity,[citation needed] and some produce usable results up to ISO 25,600.[citation needed]
Tuesday, May 6, 2008
DIGITAL VS FILM CAMERA
While photographers debate over which of the two formats, digital or film, is superior, each format has it's advantages.
LET'S FINDOUT
Quality
[edit] Spatial resolution
There are many measures that can be used to assess the quality of still photographs. The most discussed of these is spatial resolution, i.e. the number of separate points in the photograph.[citation needed] This is measured by how many picture cells make up the photo, usually counted in the millions and hence called "megapixels".[citation needed]
The comparison of resolution between film and digital photography is complex. Measuring the resolution of both film and digital photographs depends on numerous issues. For film, this issue depends on the size of film used (35 mm, Medium format or Large format), the speed of the film used and the quality of lenses in the camera. Additionally, since film is an analogue medium, it does not have pixels so its resolution measured in pixels can only be an estimate.
Similarly, digital cameras rarely perform to their stated megapixel count.[citation needed] Other factors are important in digital camera resolution such as the actual number of pixels used to store the image, the effect of the Bayer pattern or other sensor filters on the digital sensor, and the image processing algorithm used to interpolate sensor pixels to image pixels. In addition, digital sensors are generally arranged in a rectangular pattern, making images susceptible to moire pattern artifacts, whereas film is immune to such effects due to the random orientation of grains.[citation needed]
Estimates of the resolution of a photograph taken with a 35 mm film camera vary. It is possible for more resolution to be recorded if, for example, a finer grain film and/or developer are used or less resolution to be recorded with poor quality optics or low light levels. The digital megapixel equivalent of film is highly variable and roughly depends on film speed. Slow, fine-grained 35 mm B&W films with speeds of ISO 50 to 100 have estimated megapixel equivalents of 20 to 30 megapixels. Color films (both negative and slide types) are estimated between 8 and 12 megapixels. This would place film cameras (as of 2008) well over almost all point and shoot digital cameras. However, different films with the same ISO speeds can have different linear resolutions, so a direct comparison to digital is not easy. Resolution for 35mm film drops drastically with higher ISO ratings, particularly above ISO 400.[citation needed]
While 35 mm is the standard format for consumer cameras, many professional film cameras use Medium format or Large format (generally sheet) films which, due to the size of the film used, can boast resolution many times greater than the current top-of-the-range digital cameras. For example, it is estimated that a medium format film photograph can record around 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch)[1] which would equate to around 800 megapixels on the largest common film format, 8 × 10 inches. However, the estimate above does not take into account lens sharpness.[citation needed]
The question of photo quality often comes up when attempting to print a digital image at various sizes. The following tables can aid the consumer in determining a maximum photo print size based upon the megapixel depth[2]:
MegaPixel
Size Image Resolution Outstanding Print
fine compression Very Good Print Fair Print
1 480 x 640 - - - - Wallets Up to 4x6
1.2 768 x 1024 Wallets Up to 4x6 Up to 5x7
1.5 1024 x 1280 Up to 3x5 Up to 5x7 Up to 8x10
2 1200 x 1600 Up to 4x6 Up to 8x10 Up to 10x15
3 1536 x 2048 Up to 5x7 Up to 8x12 Up to 12x18
4 1800 x 2400 Up to 6x9 Up to 11x14 Up to 16x20
5 1932 x 2580 Up to 6x9 Up to 12x18 Up to 16x24
6 2016 x 3040 Up to 8x10 Up to 12x18 Up to 20x30
7.1 2304 x 3072 Up to 8x10 Up to 16x24 Up to 24x36
8.3 2336 x 3504 Up to 10x15 Up to 20x30 Up to 30x40
10.2 2592 x 3872 Up to 11x14 Up to 24x30 Up to 30x40
10.9 2704 x 4060 Up to 11x14 Up to 24x36 Up to 36x48
16.6 3328 x 4992 Up to 12x18 Up to 36x48 Up to 48x64
When deciding between film and digital and between different types of camera you want to use for a given project, it is necessary to take into account the medium which will be used for display, and the viewing distance. For instance, if a photograph will only be viewed on a television or computer display (which can resolve only about .3 megapixels[3] and 1-2 megapixels, respectively, as of 2008. HD sets of 1080p are around 1.8mp), then the resolution provided by a low-end digital cameras may be sufficient. For standard 4 × 6 inch prints, it is debatable whether there will be any perceived quality difference between digital and film when it comes to resolution. However color film will generally have the ability to reproduce a much wider range of colors than digital sensors smaller than 3 megapixels. The difference is visible on most modern computer monitors and on traditional chemically processed prints, but may not be noticeable on output media with limited color pallets such as lower end desktop inkjet prints and even large media such as billboards. Comparisons can depend on the gamut of the output media, which can influence the perception of resolution. An output media with a smaller gamut will need to use more dpi to reproduce a given color.
[edit] Noise levels
It should be noted that a special case exists for long exposure photography - Currently available technology contributes random noise to the images taken by digital cameras, produced by thermal noise and manufacturing defects. Some digital cameras apply noise reduction to long exposure photographs to counteract this. For very long exposures it is necessary to operate the detector at low temperatures to avoid noise impacting the final image. Film grain is not affected by exposure time, although the apparent speed of the film does change with longer exposures, a phenomenon known as reciprocity failure.[citation needed]
[edit] Dynamic range
As of early 2008, many current DSLRs offer a dynamic range that is as wide or wider than film such as the Canon 5D[4], 30D[5], 40D[6], Nikon D40[7], D40x[8], D80[9], D200 [10]), and Sony A700.[11] CCDs such as Fuji's Super CCD, which combines photosites of different sizes, have also addressed this problem with a gain of a much as 3 stops of range, but this has been at the expense of decreased actual resolution.
Drawing showing the relative sizes of sensors used in most current digital cameras.
Drawing showing the relative sizes of sensors used in most current digital cameras.
[edit] Effects of sensor size
Most digital cameras, even most digital SLRs, have sensors that are smaller than a standard frame of 35 mm film. These smaller sensors have a number of effects on the captured image and the use of the camera:[13]
1. Increased depth of field.
2. Decreased light sensitivity and increased pixel noise.
3. For digital SLRs, cropping of the field of view when using lenses designed for 35 mm camera.
4. Lenses can be smaller, since they only need to project light onto a smaller image area
5. Increased degree of enlargement.
The depth of field of a camera/lens combination increases as the film/sensor size decreases. This is arguably an advantage for compact digital cameras since they are intended for taking snapshots. It means that more of the scene will be in focus than with a larger sensor, and the autofocus system does not need to be as accurate to capture an acceptable image. However, art photography often makes use of a limited depth of field to create special effects, such as isolating a subject from the background. When using a digital camera with a small sensor, the photographer would have to use a larger aperture on the lens to achieve similar amounts of "bokeh".
Light sensitivity and pixel noise are both related to pixel size, which is in turn related to sensor size and resolution. As the resolution of sensors increase, the size of the individual pixels has to decrease. This smaller pixel size means that each one collects less light and the resulting signal is amplified more to produce the final value. This amplification also includes an amount of noise in the signal. With a smaller signal, the signal-to-noise ratio decreases. Not only is more noise present in the image (relatively speaking), but the relatively higher noise floor means that less useful information can be extracted from the darker parts of the image.
Most digital SLRs use lens mounts originally designed for film cameras, commonly 35 mm. If the camera has a smaller sensor than the intended film frame, the field of view of the lens is cropped. This crop factor is often called a "focal length multiplier" since the effect can be simplified to that of multiplying the focal length of the lens. For lenses that are not "digital specific" (designed for a smaller sensor despite using the 35 mm-compatible lens mount) this has the slight beneficial side effect of only using the center part of the lens, where the image quality is normally best; the "soft edges" are cropped off.
Only a few of the most expensive digital SLRs have so-called "full-frame" sensors — a sensor the same size as a 35 mm film frame (36 × 24 mm). These larger sensors eliminate the issues of depth of field and crop factor when compared to 35 mm film cameras.
With compact digital cameras the sensors are tiny compared to DSLRs. This means that prints are extreme enlargements of the original image, and that the lens has to perform outstandingly in order to provide enough resolution to match the tiny pixels on the sensor. However, many modern compact camera lenses, even 12x "super-zoom" designs, achieve the needed sharpness. The use of a small sensor also has the effect of increasing depth of field to the extent of making images very "flat" looking because backgrounds can not be blurred except for subjects very close to the camera.
Convenience and flexibility
Digital photography is flexible to the extreme; a photographer can change anything about a photograph after it has been taken.
Digital photography is flexible to the extreme; a photographer can change anything about a photograph after it has been taken.
These two pictures are a before and after demonstrating the capabilities of the digital photographer.
These two pictures are a before and after demonstrating the capabilities of the digital photographer.
This has been one of the major drivers of the widespread adoption of digital cameras. Before the advent of digital cameras, once a photograph was taken, the roll of film would need to be finished and sent off to a lab to be developed. Only once the film was returned was it possible to see the photograph. However, most digital cameras incorporate an LCD screen which allows the photograph to be viewed immediately after it has been taken. This allows the photographer to delete undesired or unnecessary photographs, and offers an immediate opportunity to re-take. When a user desires prints, it is only necessary to print the good photographs.
Another major advantage of digital technology is that photographs can be conveniently moved to a personal computer for modification. Many professional-grade digital cameras are capable of storing pictures in a Camera RAW format which stores the output from the sensor directly rather than processing it immediately to an image. When edited in suitable software, such as Adobe Photoshop or dcraw, the photographer can manipulate certain parameters of the taken photograph (such as contrast, sharpness or color balance) before it is "developed" into a final image. Less sophisticated users may choose to simply "touch up" the actual content of the recorded image;[citation needed] software with which to do this is often provided
Price
The two formats (film and digital) have different cost emphases. With digital photography, cameras tend to be significantly more expensive than film ones,[citation needed] comparing like for like. This is offset by the fact that taking photographs is effectively cost-free.
With film photography, good-quality cameras tend to be less complicated and, therefore, less expensive, but at the expense of ongoing film and processing costs. In particular, film cameras offer no chance to review photographs immediately after they are shot, and all photos taken must be processed before knowing anything about the quality of the final photograph.
However, there are additional costs associated with digital photography. Digital cameras make heavy use of batteries, some of which are proprietary and expensive.[citation needed] Whilst rechargeable, they degrade over time and must be periodically replaced. Although there is no film in digital cameras, they must store the images on memory cards or microdrives, which also have limited life. Additionally, some provision for long-term storage of the digital image must be made.[citation needed] This may be either an optical disc produced by a shop or photofinisher, or on the photographer's computer system.
With many photographers switching to digital, many film cameras (and associated equipment like lenses) are now available on the second-hand market (especially online auction sites like eBay) at often very reduced prices. This has allowed people on a budget to own a quality film camera when they might not have been able to afford the digital equivalent. Or alternatively, they are able to purchase more equipment (e.g lenses, filters, etc) than they could have with a digital camera.[citation needed]
The price differential between the two formats is often dictated by the intent of the photographer and the purpose of the work.[citation needed]
Robustness
Dust on the image plane is a constant issue for photographers. DSLR cameras are especially prone to dust problems because the sensor is reused for every shot, where a film SLR will effectively have a new "sensor" slid into place for every shot. A fresh, dust free film frame comes at risk of debris such as dust or sand in the camera scratching the film. A single grain of sand can damage a whole roll of film. Also as film SLRs age, they can develop burs in their rollers. With a digital SLRs dust is difficult to avoid, but easy rectify if one has a computer with photo editing software available. Some digital SLRs have systems that remove dust from the sensor by vibrating or knocking the sensor. Some cameras do this in conjunction with software that remembers where dust is located on the sensor and removes dust-affected pixels from images.
One huge advantage to compact point and shoot digital cameras is that they are exclusively available with fixed lenses, so dust is not an issue for them. This is not true of point an shoot film cameras, which are often only light tight and not environmentally sealed.
Archiving
When choosing between film and digital formats, one may need to consider the suitability of each as an archival medium.
Films and prints processed and stored in ideal conditions have demonstrated an ability to remain substantially unchanged for more than 100 years. Gold or platinum toned prints probably have a lifespan limited only by the lifespan of the base material, probably many hundreds of years.
The archival potential of digital photographs is less well understood since digital media have existed for only the last 50 years. There exist three problems which must be overcome for archival usage: physical stability of the recording medium, future readability of the storage medium and future readability of the file formats used for storage.
Many digital media are not capable of storing data for prolonged periods of time. For example, magnetic disks and tapes may lose their data after twenty years, flash memory cards even less. Good quality optical media may be the most durable storage media for digital data.
It is important to consider the future readability of storage media. Assuming the storage media can continue to hold data for prolonged periods of time, the short lifespan of digital technologies often causes the drives to read media to become unavailable. For example, the first 5¼-inch Floppy disks were first made available in 1976. However, the drives to read them are already extremely rare just 30 years later.
It must also be considered whether there still exists software which can decode the data. For example, many modern digital cameras save photographs in JPEG format. This format has existed for only around 15 years. Whether it will still be readable in a century is unknown, although the huge number of JPEG files currently being produced will surely influence this issue.
Most professional cameras can save in a RAW image format, the future of which is much more uncertain. Some of these formats contain proprietary data which is encrypted or protected by patents, and could be abandoned by their makers at any time for simple economic reasons. This could make it difficult to read these 'raw' files in the future, unless the camera makers were to release information on the file formats.
However, digital archives have several methods of overcoming such obstacles. In order to counteract the file format problems, many organizations prefer to choose an open and popular file format. Doing so increases the chance that software will exist to decode the file in the future.[citation needed]
Additionally many organizations take an active approach to archiving rather than relying on formats being readable decades later. This takes advantage of the ability to make perfect copies of digital media. So, for example, rather than leaving data on a format which may potentially become unreadable or unsupported, the information can typically be copied to newer media without loss of quality. This is only possible with digital media.[citation needed]
And, of course, the digital images can always be printed out and saved like traditional photographs although there are few , if any, commercial services available producing true silver halide prints from digital sources. All dye based prints, as noted above, have only limited permanence (with the exception of Cibachrome).[citation needed]
Integrity
Film produces a first generation image, which contains only the information admitted through the aperture of the camera. Film "sees" in color, in a specific spectral band such as orthochromatic, or in broad panchromatic sensitivity. Differences in development technique can produce subtle changes in the finished negative or positive, but once this process is complete it is considered permanent.
Film images are very difficult to fabricate, thus in law enforcement and in cases where the authenticity of an image is important (passport or visa photographs), film provides greater security over digital, which has the disadvantage that photographs can be conveniently moved to a personal computer for modification.
Nikon film scanner, right, which converts 35mm film images to digital
Nikon film scanner, right, which converts 35mm film images to digital
Converting film to digital
Film photographs may be digitized in a process known as scanning. They may then be manipulated as digital photographs.
There are currently three ways to scan or convert a film image to digital format.[citation needed] The first is through a reflective image scanner. Inexpensive flatbed scanners, depending upon the model used, can scan a paper-sized image from 8" x 14" to ledger size, 11" x 17". An expensive and very high resolution drum scanner can also be used to scan reflective and transparent images.
The second method is to use a dedicated film scanner, such as the Nikon Coolscan (pictured) which can scan 35 mm transparencies and negatives. Other film scanners can scan 120 film, typically up to 6 x 7 cm or 6 x 9 cm.
The third method is to take a digital photograph of the source image. One can mount a digital camera on a copy stand (or an old enlarger with its projection head removed) and photograph the source image. It is also possible to use a slide projector to project the image from a transparency and then take a digital photograph of the projection.
LET'S FINDOUT
Quality
[edit] Spatial resolution
There are many measures that can be used to assess the quality of still photographs. The most discussed of these is spatial resolution, i.e. the number of separate points in the photograph.[citation needed] This is measured by how many picture cells make up the photo, usually counted in the millions and hence called "megapixels".[citation needed]
The comparison of resolution between film and digital photography is complex. Measuring the resolution of both film and digital photographs depends on numerous issues. For film, this issue depends on the size of film used (35 mm, Medium format or Large format), the speed of the film used and the quality of lenses in the camera. Additionally, since film is an analogue medium, it does not have pixels so its resolution measured in pixels can only be an estimate.
Similarly, digital cameras rarely perform to their stated megapixel count.[citation needed] Other factors are important in digital camera resolution such as the actual number of pixels used to store the image, the effect of the Bayer pattern or other sensor filters on the digital sensor, and the image processing algorithm used to interpolate sensor pixels to image pixels. In addition, digital sensors are generally arranged in a rectangular pattern, making images susceptible to moire pattern artifacts, whereas film is immune to such effects due to the random orientation of grains.[citation needed]
Estimates of the resolution of a photograph taken with a 35 mm film camera vary. It is possible for more resolution to be recorded if, for example, a finer grain film and/or developer are used or less resolution to be recorded with poor quality optics or low light levels. The digital megapixel equivalent of film is highly variable and roughly depends on film speed. Slow, fine-grained 35 mm B&W films with speeds of ISO 50 to 100 have estimated megapixel equivalents of 20 to 30 megapixels. Color films (both negative and slide types) are estimated between 8 and 12 megapixels. This would place film cameras (as of 2008) well over almost all point and shoot digital cameras. However, different films with the same ISO speeds can have different linear resolutions, so a direct comparison to digital is not easy. Resolution for 35mm film drops drastically with higher ISO ratings, particularly above ISO 400.[citation needed]
While 35 mm is the standard format for consumer cameras, many professional film cameras use Medium format or Large format (generally sheet) films which, due to the size of the film used, can boast resolution many times greater than the current top-of-the-range digital cameras. For example, it is estimated that a medium format film photograph can record around 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch)[1] which would equate to around 800 megapixels on the largest common film format, 8 × 10 inches. However, the estimate above does not take into account lens sharpness.[citation needed]
The question of photo quality often comes up when attempting to print a digital image at various sizes. The following tables can aid the consumer in determining a maximum photo print size based upon the megapixel depth[2]:
MegaPixel
Size Image Resolution Outstanding Print
fine compression Very Good Print Fair Print
1 480 x 640 - - - - Wallets Up to 4x6
1.2 768 x 1024 Wallets Up to 4x6 Up to 5x7
1.5 1024 x 1280 Up to 3x5 Up to 5x7 Up to 8x10
2 1200 x 1600 Up to 4x6 Up to 8x10 Up to 10x15
3 1536 x 2048 Up to 5x7 Up to 8x12 Up to 12x18
4 1800 x 2400 Up to 6x9 Up to 11x14 Up to 16x20
5 1932 x 2580 Up to 6x9 Up to 12x18 Up to 16x24
6 2016 x 3040 Up to 8x10 Up to 12x18 Up to 20x30
7.1 2304 x 3072 Up to 8x10 Up to 16x24 Up to 24x36
8.3 2336 x 3504 Up to 10x15 Up to 20x30 Up to 30x40
10.2 2592 x 3872 Up to 11x14 Up to 24x30 Up to 30x40
10.9 2704 x 4060 Up to 11x14 Up to 24x36 Up to 36x48
16.6 3328 x 4992 Up to 12x18 Up to 36x48 Up to 48x64
When deciding between film and digital and between different types of camera you want to use for a given project, it is necessary to take into account the medium which will be used for display, and the viewing distance. For instance, if a photograph will only be viewed on a television or computer display (which can resolve only about .3 megapixels[3] and 1-2 megapixels, respectively, as of 2008. HD sets of 1080p are around 1.8mp), then the resolution provided by a low-end digital cameras may be sufficient. For standard 4 × 6 inch prints, it is debatable whether there will be any perceived quality difference between digital and film when it comes to resolution. However color film will generally have the ability to reproduce a much wider range of colors than digital sensors smaller than 3 megapixels. The difference is visible on most modern computer monitors and on traditional chemically processed prints, but may not be noticeable on output media with limited color pallets such as lower end desktop inkjet prints and even large media such as billboards. Comparisons can depend on the gamut of the output media, which can influence the perception of resolution. An output media with a smaller gamut will need to use more dpi to reproduce a given color.
[edit] Noise levels
It should be noted that a special case exists for long exposure photography - Currently available technology contributes random noise to the images taken by digital cameras, produced by thermal noise and manufacturing defects. Some digital cameras apply noise reduction to long exposure photographs to counteract this. For very long exposures it is necessary to operate the detector at low temperatures to avoid noise impacting the final image. Film grain is not affected by exposure time, although the apparent speed of the film does change with longer exposures, a phenomenon known as reciprocity failure.[citation needed]
[edit] Dynamic range
As of early 2008, many current DSLRs offer a dynamic range that is as wide or wider than film such as the Canon 5D[4], 30D[5], 40D[6], Nikon D40[7], D40x[8], D80[9], D200 [10]), and Sony A700.[11] CCDs such as Fuji's Super CCD, which combines photosites of different sizes, have also addressed this problem with a gain of a much as 3 stops of range, but this has been at the expense of decreased actual resolution.
Drawing showing the relative sizes of sensors used in most current digital cameras.
Drawing showing the relative sizes of sensors used in most current digital cameras.
[edit] Effects of sensor size
Most digital cameras, even most digital SLRs, have sensors that are smaller than a standard frame of 35 mm film. These smaller sensors have a number of effects on the captured image and the use of the camera:[13]
1. Increased depth of field.
2. Decreased light sensitivity and increased pixel noise.
3. For digital SLRs, cropping of the field of view when using lenses designed for 35 mm camera.
4. Lenses can be smaller, since they only need to project light onto a smaller image area
5. Increased degree of enlargement.
The depth of field of a camera/lens combination increases as the film/sensor size decreases. This is arguably an advantage for compact digital cameras since they are intended for taking snapshots. It means that more of the scene will be in focus than with a larger sensor, and the autofocus system does not need to be as accurate to capture an acceptable image. However, art photography often makes use of a limited depth of field to create special effects, such as isolating a subject from the background. When using a digital camera with a small sensor, the photographer would have to use a larger aperture on the lens to achieve similar amounts of "bokeh".
Light sensitivity and pixel noise are both related to pixel size, which is in turn related to sensor size and resolution. As the resolution of sensors increase, the size of the individual pixels has to decrease. This smaller pixel size means that each one collects less light and the resulting signal is amplified more to produce the final value. This amplification also includes an amount of noise in the signal. With a smaller signal, the signal-to-noise ratio decreases. Not only is more noise present in the image (relatively speaking), but the relatively higher noise floor means that less useful information can be extracted from the darker parts of the image.
Most digital SLRs use lens mounts originally designed for film cameras, commonly 35 mm. If the camera has a smaller sensor than the intended film frame, the field of view of the lens is cropped. This crop factor is often called a "focal length multiplier" since the effect can be simplified to that of multiplying the focal length of the lens. For lenses that are not "digital specific" (designed for a smaller sensor despite using the 35 mm-compatible lens mount) this has the slight beneficial side effect of only using the center part of the lens, where the image quality is normally best; the "soft edges" are cropped off.
Only a few of the most expensive digital SLRs have so-called "full-frame" sensors — a sensor the same size as a 35 mm film frame (36 × 24 mm). These larger sensors eliminate the issues of depth of field and crop factor when compared to 35 mm film cameras.
With compact digital cameras the sensors are tiny compared to DSLRs. This means that prints are extreme enlargements of the original image, and that the lens has to perform outstandingly in order to provide enough resolution to match the tiny pixels on the sensor. However, many modern compact camera lenses, even 12x "super-zoom" designs, achieve the needed sharpness. The use of a small sensor also has the effect of increasing depth of field to the extent of making images very "flat" looking because backgrounds can not be blurred except for subjects very close to the camera.
Convenience and flexibility
Digital photography is flexible to the extreme; a photographer can change anything about a photograph after it has been taken.
Digital photography is flexible to the extreme; a photographer can change anything about a photograph after it has been taken.
These two pictures are a before and after demonstrating the capabilities of the digital photographer.
These two pictures are a before and after demonstrating the capabilities of the digital photographer.
This has been one of the major drivers of the widespread adoption of digital cameras. Before the advent of digital cameras, once a photograph was taken, the roll of film would need to be finished and sent off to a lab to be developed. Only once the film was returned was it possible to see the photograph. However, most digital cameras incorporate an LCD screen which allows the photograph to be viewed immediately after it has been taken. This allows the photographer to delete undesired or unnecessary photographs, and offers an immediate opportunity to re-take. When a user desires prints, it is only necessary to print the good photographs.
Another major advantage of digital technology is that photographs can be conveniently moved to a personal computer for modification. Many professional-grade digital cameras are capable of storing pictures in a Camera RAW format which stores the output from the sensor directly rather than processing it immediately to an image. When edited in suitable software, such as Adobe Photoshop or dcraw, the photographer can manipulate certain parameters of the taken photograph (such as contrast, sharpness or color balance) before it is "developed" into a final image. Less sophisticated users may choose to simply "touch up" the actual content of the recorded image;[citation needed] software with which to do this is often provided
Price
The two formats (film and digital) have different cost emphases. With digital photography, cameras tend to be significantly more expensive than film ones,[citation needed] comparing like for like. This is offset by the fact that taking photographs is effectively cost-free.
With film photography, good-quality cameras tend to be less complicated and, therefore, less expensive, but at the expense of ongoing film and processing costs. In particular, film cameras offer no chance to review photographs immediately after they are shot, and all photos taken must be processed before knowing anything about the quality of the final photograph.
However, there are additional costs associated with digital photography. Digital cameras make heavy use of batteries, some of which are proprietary and expensive.[citation needed] Whilst rechargeable, they degrade over time and must be periodically replaced. Although there is no film in digital cameras, they must store the images on memory cards or microdrives, which also have limited life. Additionally, some provision for long-term storage of the digital image must be made.[citation needed] This may be either an optical disc produced by a shop or photofinisher, or on the photographer's computer system.
With many photographers switching to digital, many film cameras (and associated equipment like lenses) are now available on the second-hand market (especially online auction sites like eBay) at often very reduced prices. This has allowed people on a budget to own a quality film camera when they might not have been able to afford the digital equivalent. Or alternatively, they are able to purchase more equipment (e.g lenses, filters, etc) than they could have with a digital camera.[citation needed]
The price differential between the two formats is often dictated by the intent of the photographer and the purpose of the work.[citation needed]
Robustness
Dust on the image plane is a constant issue for photographers. DSLR cameras are especially prone to dust problems because the sensor is reused for every shot, where a film SLR will effectively have a new "sensor" slid into place for every shot. A fresh, dust free film frame comes at risk of debris such as dust or sand in the camera scratching the film. A single grain of sand can damage a whole roll of film. Also as film SLRs age, they can develop burs in their rollers. With a digital SLRs dust is difficult to avoid, but easy rectify if one has a computer with photo editing software available. Some digital SLRs have systems that remove dust from the sensor by vibrating or knocking the sensor. Some cameras do this in conjunction with software that remembers where dust is located on the sensor and removes dust-affected pixels from images.
One huge advantage to compact point and shoot digital cameras is that they are exclusively available with fixed lenses, so dust is not an issue for them. This is not true of point an shoot film cameras, which are often only light tight and not environmentally sealed.
Archiving
When choosing between film and digital formats, one may need to consider the suitability of each as an archival medium.
Films and prints processed and stored in ideal conditions have demonstrated an ability to remain substantially unchanged for more than 100 years. Gold or platinum toned prints probably have a lifespan limited only by the lifespan of the base material, probably many hundreds of years.
The archival potential of digital photographs is less well understood since digital media have existed for only the last 50 years. There exist three problems which must be overcome for archival usage: physical stability of the recording medium, future readability of the storage medium and future readability of the file formats used for storage.
Many digital media are not capable of storing data for prolonged periods of time. For example, magnetic disks and tapes may lose their data after twenty years, flash memory cards even less. Good quality optical media may be the most durable storage media for digital data.
It is important to consider the future readability of storage media. Assuming the storage media can continue to hold data for prolonged periods of time, the short lifespan of digital technologies often causes the drives to read media to become unavailable. For example, the first 5¼-inch Floppy disks were first made available in 1976. However, the drives to read them are already extremely rare just 30 years later.
It must also be considered whether there still exists software which can decode the data. For example, many modern digital cameras save photographs in JPEG format. This format has existed for only around 15 years. Whether it will still be readable in a century is unknown, although the huge number of JPEG files currently being produced will surely influence this issue.
Most professional cameras can save in a RAW image format, the future of which is much more uncertain. Some of these formats contain proprietary data which is encrypted or protected by patents, and could be abandoned by their makers at any time for simple economic reasons. This could make it difficult to read these 'raw' files in the future, unless the camera makers were to release information on the file formats.
However, digital archives have several methods of overcoming such obstacles. In order to counteract the file format problems, many organizations prefer to choose an open and popular file format. Doing so increases the chance that software will exist to decode the file in the future.[citation needed]
Additionally many organizations take an active approach to archiving rather than relying on formats being readable decades later. This takes advantage of the ability to make perfect copies of digital media. So, for example, rather than leaving data on a format which may potentially become unreadable or unsupported, the information can typically be copied to newer media without loss of quality. This is only possible with digital media.[citation needed]
And, of course, the digital images can always be printed out and saved like traditional photographs although there are few , if any, commercial services available producing true silver halide prints from digital sources. All dye based prints, as noted above, have only limited permanence (with the exception of Cibachrome).[citation needed]
Integrity
Film produces a first generation image, which contains only the information admitted through the aperture of the camera. Film "sees" in color, in a specific spectral band such as orthochromatic, or in broad panchromatic sensitivity. Differences in development technique can produce subtle changes in the finished negative or positive, but once this process is complete it is considered permanent.
Film images are very difficult to fabricate, thus in law enforcement and in cases where the authenticity of an image is important (passport or visa photographs), film provides greater security over digital, which has the disadvantage that photographs can be conveniently moved to a personal computer for modification.
Nikon film scanner, right, which converts 35mm film images to digital
Nikon film scanner, right, which converts 35mm film images to digital
Converting film to digital
Film photographs may be digitized in a process known as scanning. They may then be manipulated as digital photographs.
There are currently three ways to scan or convert a film image to digital format.[citation needed] The first is through a reflective image scanner. Inexpensive flatbed scanners, depending upon the model used, can scan a paper-sized image from 8" x 14" to ledger size, 11" x 17". An expensive and very high resolution drum scanner can also be used to scan reflective and transparent images.
The second method is to use a dedicated film scanner, such as the Nikon Coolscan (pictured) which can scan 35 mm transparencies and negatives. Other film scanners can scan 120 film, typically up to 6 x 7 cm or 6 x 9 cm.
The third method is to take a digital photograph of the source image. One can mount a digital camera on a copy stand (or an old enlarger with its projection head removed) and photograph the source image. It is also possible to use a slide projector to project the image from a transparency and then take a digital photograph of the projection.
COLOR TEMPERATURE
Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. The color temperature of a light source is determined by comparing its chromaticity with a theoretical, heated black-body radiator. The temperature (usually measured in kelvin (K)) at which the heated black-body radiator matches the color of the light source is that source's color temperature; for a black body source, it is directly related to Planck's law.
Wednesday, April 30, 2008
Lenses and it's functions
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Lenses are often referred to by terms that express their angle of view:
- Ultra wide-angle lenses, also known as fisheye lenses, cover up to 180° (or even wider in special cases)
- Wide-angle lenses generally cover between 100° and 60°
- Normal, or Standard lenses generally cover between 50° and 25°
- Telephoto lenses generally cover between 15° and 10°
- Super Telephoto lenses generally cover between 8° through less than 1°
Zoom lenses are a special case wherein the focal length, and hence angle of view, of the lens can be altered mechanically without removing the lens from the camera.
Longer lenses magnify the subject more, apparently compressing distance and (when focused on the foreground) blurring the background because of their shallower depth of field. Wider lenses tend to magnify distance between objects while allowing greater depth of field.
Another result of using a wide angle lens is a greater apparent perspective distortion when the camera is not aligned perpendicularly to the subject: parallel lines converge at the same rate as with a normal lens, but converge more due to the wider total field. For example, buildings appear to be falling backwards much more severely when the camera is pointed upward from ground level than they would if photographed with a normal lens at the same distance from the subject, because more of the subject building is visible in the wide-angle shot.
Because different lenses generally require a different camera–subject distance to preserve the size of a subject, changing the angle of view can indirectly distort perspective, changing the apparent relative size of the subject and foreground.
 28 mm lens, 65.5° × 46.4° |  50 mm lens, 39.6° × 27.0° |
 70 mm lens, 28.9° × 19.5° |  210 mm lens, 9.8° × 6.5° |
Circular fisheye
A circular fisheye lens (as opposed to a full-frame fisheye) is an example of a lens where the angle of coverage is less than the angle of view. The image projected onto the film is circular because the diameter of the image projected is narrower than that needed to cover the widest portion of the film.
Common lens angles of view
This table shows the diagonal, horizontal, and vertical angles of view, in degrees, for lenses producing rectilinear images, when used with 36 mm × 24 mm format (that is, 135 film or full-frame 35mm digital using width 36 mm, height 24 mm, and diagonal 43.3 mm for d in the formula above[5]).
| Focal Length (mm) | 13 | 15 | 18 | 21 | 24 | 28 | 35 | 50 | 85 | 105 | 135 | 180 | 210 | 300 | 400 | 500 | 600 | 830 | 1200 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Diagonal (°) | 118 | 111 | 100 | 91.7 | 84.1 | 75.4 | 63.4 | 46.8 | 28.6 | 23.3 | 18.2 | 13.7 | 11.8 | 8.25 | 6.19 | 4.96 | 4.13 | 2.99 | 2.07 |
| Vertical (°) | 85.4 | 77.3 | 67.4 | 59.5 | 53.1 | 46.4 | 37.8 | 27.0 | 16.1 | 13.0 | 10.2 | 7.63 | 6.54 | 4.58 | 3.44 | 2.75 | 2.29 | 1.66 | 1.15 |
| Horizontal (°) | 108 | 100.4 | 90.0 | 81.2 | 73.7 | 65.5 | 54.4 | 39.6 | 23.9 | 19.5 | 15.2 | 11.4 | 9.80 | 6.87 | 5.15 | 4.12 | 3.44 | 2.48 | 1.72 |
Three-dimensional digital art
Displaying 3d graphics requires 3d projection of the models onto a 2d surface, and uses a series of mathematical calculations to render the scene. The angle of view of the scene is thus readily set and changed; some renderers even measure the angle of view as the focal length of an imaginary lens. The angle of view can also be projected onto the surface at an angle greater than 90°, effectively creating a fish eye lens effect.
Cinematography
Modifying the angle of view over time, or zooming, is a frequently used cinematic technique.
Video games
As an effect, some first person games, especially racing games, widen the angle of view beyond 90° to exaggerate the distance the player is travelling, thus exaggerating the player's perceived speed. This effect can be done progressively, or upon the activation of some sort of "turbo boost." An interesting visual effect in itself, it also provides a way for game developers to suggest speeds faster than the game engine or computer hardware is capable of displaying. Some examples include Burnout 3: Takedown and Grand Theft Auto: San Andreas.
Players of first-person shooter games sometimes set the angle of view of the game, widening it in an unnatural way (a difference of 20 or 30 degrees from normal), in order to see more peripherally.
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Calculating angle of view
Calculating a camera's angle of view
For lenses projecting rectilinear (non-spatially-distorted) images of distant objects, the effective focal length and the image format dimensions completely define the angle of view. Calculations for lenses producing non-rectilinear images are much more complex and in the end not very useful in most practical applications.
Angle of view may be measured horizontally (from the left to right edge of the frame), vertically (from the top to bottom of the frame), or diagonally (from one corner of the frame to its opposite corner).
For a lens projecting a rectilinear image, the angle of view (α) can be calculated from the chosen dimension (d), and effective focal length (f) as follows:[3]
Because this is a trigonometric function, the angle of view does not vary quite linearly with the reciprocal of the focal length. However, except for wide-angle lenses, it is reasonable to approximate 
The effective focal length is nearly equal to the stated focal length of the lens (F), except in macro photography where the lens-to-object distance is comparable to the focal length. In this case, the magnification factor (m) must be taken into account:
(In photography m is usually defined to be positive, despite the inverted image.) For example, with a magnification ratio of 1:2, we find 
[edit] Example
Consider a 35 mm camera with a normal lens having a focal length of F=50 mm. The dimensions of the 35 mm image format are 24 mm (vertically) × 36 mm (horizontal), giving a diagonal of about 43.3 mm.
Now the angles of view are:
- horizontally,
39.6°
- vertically,
27.0°
- diagonally,
46.7°
[edit] Derivation of the angle-of-view formula
Consider a rectilinear lens in a camera used to photograph an object at a distance S1, and forming an image that just barely fits in the dimension d of the frame (the film or image sensor). Treat the lens as if it were a pinhole at distance S2 from the image plane (technically, the center of perspective of a rectilinear lens is at the center of its entrance pupil[4]):
Now α / 2 is the angle between the optical axis of the lens and the ray joining its optical center to the edge of the film. Here α is defined to be the angle-of-view, since it is the angle enclosing the largest object whose image can fit on the film. We want to find the relationship between:
-
- the angle α (half of the angle-of-view)
- the "opposite" side of the right triangle, d / 2 (half the film-format dimension)
- the "adjacent" side, S2 (distance from the lens to the image plane)
Using basic trigonometry, we find:
which we can solve for α, giving:
To project a sharp image of distant objects, S2 needs to be equal to the focal length F, which is attained by setting the lens for infinity focus. Then the angle of view is given by:
-
where f = F
[edit] Macro photography
For macro photography, we cannot neglect the difference between S2 and F From the thin lens formula,
-
.
We substitute for the magnification, m = S2 / S1, and with some algebra find:
Defining f = S2 as the "effective focal length", we get the formula presented above:
-
.
Principles of photography
ANGLE OF VIEW
In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It parallels, and may be used interchangeably with, the more general visual term field of view.
It is important to distinguish the angle of view from the angle of coverage, which describes the angle of projection by the lens onto the focal plane. For most cameras, it may be assumed that the image circle produced by the lens is large enough to cover the film or sensor completely.[1] If the angle of view exceeds the angle of coverage, however, then vignetting will be present in the resulting photograph. For an example of this, see below.
Angle_of_view.svg (SVG file, nominally 425 × 351 pixels, file size: 9 KB)
Types of photography
Photography types
Black-and-white photography
"Casting Winds" - this black & white displays the classic monochrome look, as well as the use of simulated optical filtering (wratten #25) to enhance or diminish the rendering of certain light wavelengths.
All photography was originally monochrome, or black-and-white. Even after color film was readily available, black-and-white photography continued to dominate for decades, due to its lower cost and its "classic" photographic look. It is important to note that some monochromatic pictures are not always pure blacks and whites but contain other hues depending on the process. The Cyanotype process produces an image of blue and white for example.
Many photographers continue to produce some monochrome images. Some full color digital images are processed using a variety of techniques to create black and whites, and some cameras have even been produced to exclusively shoot monochrome. (See also Monochrome Photography).
Color photography
Color photography was explored beginning in the mid 1800s. Early experiments in color could not fix the photograph and prevent the color from fading. The first permanent color photo was taken in 1861 by the physicist James Clerk Maxwell.
Early color photograph taken by Prokudin-Gorskii (1915)
One of the early methods of taking color photos was to use three cameras. Each camera would have a color filter in front of the lens. This technique provides the photographer with the three basic channels required to recreate a color image in a darkroom or processing plant. Russian photographer Sergei Mikhailovich Prokudin-Gorskii developed another technique, with three color plates taken in quick succession.
Practical application of the technique was held back by the very limited color response of early film; however, in the early 1900s, following the work of photo-chemists such as H. W. Vogel, emulsions with adequate sensitivity to green and red light at last became available.
The first color plate, Autochrome, invented by the French Lumière brothers, reached the market in 1907. It was based on a 'screen-plate' filter made of dyed dots of potato starch, and was the only color film on the market until German Agfa introduced the similar Agfacolor in 1932. In 1935, American Kodak introduced the first modern ('integrated tri-pack') color film, Kodachrome, based on three colored emulsions. This was followed in 1936 by Agfa's Agfacolor Neue. Unlike the Kodachrome tri-pack process the color couplers in Agfacolor Neue were integral with the emulsion layers, which greatly simplified the film processing. Most modern color films, except Kodachrome, are based on the Agfacolor Neue technology. Instant color film was introduced by Polaroid in 1963.
Color photography may form images as a positive transparency, intended for use in a slide projector or as color negatives, intended for use in creating positive color enlargements on specially coated paper. The latter is now the most common form of film (non-digital) color photography owing to the introduction of automated photoprinting equipment.
Digital photography
- See also: Digital versus film photography
Nikon digital camera and scanner, which converts film images to digital
Traditional photography burdened photographers working at remote locations without easy access to processing facilities, and competition from television pressured photographers to deliver images to newspapers with greater speed. Photo journalists at remote locations often carried miniature photo labs and a means of transmitting images through telephone lines. In 1981, Sony unveiled the first consumer camera to use a charge-coupled device for imaging, eliminating the need for film: the Sony Mavica. While the Mavica saved images to disk, the images were displayed on television, and the camera was not fully digital. In 1990, Kodak unveiled the DCS 100, the first commercially available digital camera. Although its high cost precluded uses other than photojournalism and professional photography, commercial digital photography was born.
Digital imaging uses an electronic image sensor to record the image as a set of electronic data rather than as chemical changes on film. The primary difference between digital and chemical photography is that analog photography resists manipulation because it involves film, optics and photographic paper, while digital imaging is a highly manipulative medium. This difference allows for a degree of image post-processing that is comparatively difficult in film-based photography and permits different communicative potentials and applications.
Digital point-and-shoot cameras have become widespread consumer products, outselling film cameras, and including new features such as video and audio recording. Kodak announced in January 2004 that it would no longer sell reloadable 35 mm cameras in western Europe, Canada and the United States after the end of that year. Kodak was at that time a minor player in the reloadable film cameras market. In January 2006, Nikon followed suit and announced that they will stop the production of all but two models of their film cameras: the low-end Nikon FM10, and the high-end Nikon F6. On May 25, 2006, Canon announced they will stop developing new film SLR cameras.[3]
According to a survey made by Kodak in 2007, 75 percent of professional photographers say they will continue to use film, even though some embrace digital.[4]
According to the U.S. survey results, more than two-thirds (68 percent) of professional photographers prefer the results of film to those of digital for certain applications including:
- film’s superiority in capturing more information on medium and large format films (48 percent);
- creating a traditional photographic look (48 percent);
- capturing shadow and highlighting details (45 percent);
- the wide exposure latitude of film (42 percent); and
- archival storage (38 percent)
Because photography is popularly synonymous with truth ("The camera doesn't lie."), digital imaging has raised many ethical concerns. Many photojournalists have declared they will not crop their pictures, or are forbidden from combining elements of multiple photos to make "illustrations," passing them as real photographs. Many courts will not accept digital images as evidence because of their inherently manipulative nature. Today's technology has made picture editing relatively simple for even the novice photographer.
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