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Image sensor format
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Comparative dimensions of sensor sizes
In digital photography, the image sensor format is the shape and size of the image sensor.
The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular camera. In particular, image sensors in digital SLR cameras tend to be smaller than the 24 mm x 36 mm image area of full-frame 35 mm cameras, and therefore lead to a narrower angle of view.
Lenses produced for 35 mm film cameras may mount well on the digital bodies, but the larger image circle of the 35 mm system lens allows
unwanted light into the camera body, and the smaller size of the image sensor compared to 35 mm format results in cropping of the image compared to the results produced on the film camera. This latter effect is known as field-of-view crop; the format size ratio is known as the field of view crop factor, crop factor for short, or focal-length multiplier.
Contents
[hide] (^) 1 Sensor size (^) 2 Sensor size vs. lens size and depth of field (^) 3 Common image sensor formats (^) 3.1 DSLR/MILC formats (^) 3.2 Medium-format DSLR (^) 3.3 Compact digital camera formats (^) 3.4 Table of sensor sizes (^) 4 Bridging the gap in sensor sizes (^) 5 See also (^) 6 Notes and references (^) 7 External links
[edit] Sensor size
All other things being equal, a larger sensor captures images with greater
zoom lens. Another reason for this huge difference is that old-time full- frame compact-zoom film-cameras were meant mainly to produce 10x cm. prints. Digital shots, instead, end up being viewed at high magnification on large screens. So lenses feeding sensors must do a particularly good job, which comes at a price. Bulk included.
Sensor size inversely affects depth of field (the larger the sensor, the shallower the d.o.f.). In other words, larger sensors allow a more marked Bokeh , a much sought-after effect by professional photographers and photo-enthusiasts. As a consequence, though, cameras using large sensors need a particularly accurate focusing (which, in turn, may translate into further bulk, system costs and lens quality issues).
[edit] Common image sensor formats
Sizes of the sensors used in most current digital cameras relative to a standard 35mm frame.
[edit] DSLR/MILC formats
Some professional DSLRs use full-frame sensors, equal to the size of a frame of 35 mm film.
Most consumer-level DSLRs and MILCs/EVILs use relatively large sensors, either around the size of a frame of APS-C film, with a crop factor
(^) Four Thirds System format (crop factor 2.0) (^) Nikon CX format used in Nikon 1 series (crop factor 2.7)
Production costs for a full frame sensor can exceed twenty times the costs of an APS-C sensor. Only about thirty full-frame sensors can be produced on an 8 inches (20 cm) silicon wafer that would fit 112 APS-C sensors, and there is a significant reduction in yield due to the large area for contaminants per component. Additionally, the full frame sensor requires three separate exposures during the photolithography stage, which requires separate masks and quality control steps. The APS-H size was selected since it is the largest that can be imaged with a single mask to help control production costs and manage yields.[2]
Due to the ever-changing constraints of semiconductor fabrication and processing, and because camera manufacturers often source sensors from third-party foundries, it is common for sensor dimensions to vary slightly within the same nominal format. For example, the Nikon D3 and D cameras' nominally full-frame sensors actually measure 36 × 23.9 mm, slightly smaller than a frame of 35 mm film. As another example, the Pentax K200D's sensor (made by Sony) measures 23.5 × 15.7 mm, while the contemporaneous K20D's sensor (made by Samsung) measures 23.4 × 15. mm.
Most DSLR image sensor formats approximate the 3:2 aspect ratio of 35 mm film. Again, the Four Thirds System is a notable exception, with an aspect ratio of 4:3 as seen in most compact digital cameras (see below).
[edit] Medium-format DSLR
The most common sensor size for medium-format digital cameras is approximately 48 × 36 mm (1.9 × 1.4 in)[ citation needed ], due to the widespread use of Kodak's 22-megapixel KAF-22000 and 39-megapixel KAF-39000[3] CCDs in that format. Phase one offers the P65+ digital back with Dalsa's 53.9 × 40.4 mm (2.12 × 1.59 in) 16-bit sensor containing 60.5 megapixels[4] and Leica offers an "S-System" DSLR with a 45 × 30 mm (1.8 × 1.2 in) sensor containing 37-megapixels.[5]^ In 2010, Pentax released the 40MP 645D medium format DSLR with a 44 × 33 mm (1.7 × 1.3 in) sensor.[6]
[edit] Compact digital camera formats
The sensor sizes of many compact digital cameras are expressed in terms of the non-standardized "inch" system, as approximately 1.5 times the length of the diagonal of the sensor. This goes back to the way image sizes of early video cameras were expressed in terms of the outside diameter of the glass envelope of the video camera tube. David Pogue of the New York Times states that "the actual sensor size is much smaller than what the camera companies publish — about one-third smaller." For example, a camera advertising a 1/2.7" sensor does not have a sensor with a diagonal of 0.37"; instead, the diagonal is closer to 0.26".[7][8]^ Instead of "formats", these sensor sizes are often called types , as in "1/2-inch-type CCD." Most compact image sensors have an aspect ratio of 4:3. This matches the aspect ratio of the popular VGA, SVGA, and XGA display resolutions, allowing images to be displayed on most computer monitors without cropping.
As of December 2010, most compact digital cameras use 1/2.5" or 1/2.3"
[edit] Table of sensor sizes
Inch-based sensor formats are not standardized. Originally, they were the outer diameters of image tubes used in the 1950s. Exact dimensions may vary, but those listed are typical.[8]
Ty pe
S
u pe r 1 6 m m
N
ik o n C [9]X
m /3 · 4/ " (Fo ur Th ird s)
Si g m a F ov eo n X 3
C
an o n A P S- C
Sony · Pentax · Sigma · Samsung APS-C / Nikon DX
C
an o n A P S- H
m m F ul l- fr a m e / N ik o n F X
L
ei c a S 2
P
en ta x 64 5 D
K
od ak K A F 39 00 0 C C [10]D
L
e af A F i 1 0
P
h as e O n e P 6 5 +
Di ag on al (m m)
W
idt h (m m)
He ig ht (m m)
Ar ea (m m^2 )
mount. Other companies followed suit, by introducing similar cameras that focus electronically rather than manually (such as Olympus, with its PEN series; Panasonic, with its G and GF series; Sony, with its Nex series; Samsung, with its NX series). Such cameras might overall look like compact digital ones, with at least two notable differences: a sensor of the size found in digital SLRs, and interchangeable lenses.
The latter feature, though, is now to be found in at least one small-sensor compact camera as well (Pentax Q, announced on June 2011). Whereas a new mirrorless interchangeable-lens camera (MILC), equipped with an unedited sensor size (1", CX format), has just been annouced (Sep. 2011).
For years on a large gap existed in sensor size between digital compact cameras on one side and DSLRs/MILCs on the other. The former were all equipped with sensors smaller than 1/1.6" (48.5 mm^2 ), whereas 4/3" ( mm^2 ) was the smallest sensor to be found on DSLRs/MILCs.
The main reason for such a gap was portability: large sensors imply the need of bulky lenses (to provide large, high-quality images made up of rays hitting the photoreceptors at not too steep an angle). That's why MILC cameras tend to show a marked disproportion between their tiny bodies and their imposing lens systems (their zoom objectives especially).
The above mentioned gap was at last bridged by camera models announced in September 2011.
On the compact side of the gap, a very large (for a compact) 2/3" (58. mm^2 ) sensor will equip the high-end compact announced by Fuji on Sep. 1st 2011 (Fuji X10). At the same time, on the other (DSLR/MILC) side of
the collapsing chasm, Nikon announced (in September 2011) the Nikon 1 system , built around a new sensor format they named 'CX' (13.2mm x 8.8mm, that is roughly 1" in the inch system ).
How much this new breed of MILCs will, in addressing the lens-bulk issue, compromise the typical advantages associated with larger sensors (such as high-ISO performance) has yet to be seen at the time of writing. In any case, such format additions (the 'CX' especially) have now eliminated the previous gap in sensor sizes: the crop factor difference now existing between the largest compact camera sensor (2/3", 3.9 c.f.) and the smallest MILC sensor (1", 2.7 c.f.) is about half the one previously existing between 1/1.6" and 4/3" sensors.
[edit] See also
(^) Full-frame digital SLR (^) Depth of field vs. format size (^) Sensor size and angle of view (^) 35 mm equivalent focal length (^) Film format
[edit] Notes and references
(^) ^ http://www.dpreview.com/news/1109/11092119nikonJ1.asp#press (^) ^ "Canon's Full Frame CMOS Sensors" (Press release). Canon.
http://www.usa.canon.com/uploadedimages/FCK/Image/White%
(^) ^ Nikon 1 J1 Camera. Tech Specs , September 21, 2011, http://www.nikonusa.com/Nikon- Products/Product/Nikon1/V27528/Nikon-1-J1.html#tab- ProductDetail.ProductTabs.TechSpecs (^) ^ KODAK KAF-39000 IMAGE SENSOR, DEVICE PERFORMANCE SPECIFICATION , April 21, 2010, http://www.kodak.com/global/plugins/acrobat/en/business/ISS/dat asheet/fullframe/KAF-39000LongSpec.pdf (^) ^ Defined here as the ratio of the diagonal of a full 35 frame to that of the sensor format, that is CF=diag35mm / diagsensor.
[edit] External links
(^) Compact Camera High ISO modes: Separating the facts from the hype (May 2007) (^) The «Mass» of Pixels or the «Mess» of Pixels? at 6mpixel.org
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