APS-C

The Nikon D70, a typical APS-C format camera

Advanced Photo System type-C (APS-C) is an image sensor format approximately equivalent in size to the Advanced Photo System "classic" size negatives. These negatives were 25.1 × 16.7 mm and had an aspect ratio 3:2.

Sensors meeting these approximate dimensions are used in many digital single-lens reflex cameras, in addition to a few large-sensored live-preview digital cameras (such as the Sony DSC-R1, Sigma DP1 and Leica X1) and a few digital rangefinders (e.g. the Epson R-D1). Such sensors exist in many different variants depending on the manufacturer and camera model. All APS-C variants are considerably smaller than 35 mm standard film which measures 36×24 mm. Sensor sizes range from 20.7×13.8 mm to 28.7×19.1 mm. Each variant results in a slightly different angle of view from lenses at the same focal length and overall a much narrower angle of view compared to 35 mm film. This is why each manufacturer offers a range of lenses designed for its format.

Advantages and disadvantages

Compared to the full-frame format, APS-C sensors offer some advantages and disadvantages. Currently, digital SLRs using full-frame sensors are mostly used by professional photographers and serious amateurs. This may be because SLRs with APS-C sensors are considerably cheaper than full-frame cameras. They are also lighter and smaller. Apart from these differences, there are two other important factors. The first is image quality. Theoretically, a larger sensor produces a better image, i.e. one with more detail and less noise. In practice, the difference may not be obvious and may depend on the use of a high quality lens and on the photographer's skill. The other difference is the crop factor. The smaller APS-C sensor effectively minimizes the field of view by about 1.5, so that a 300mm lens has the same field of view as a 450mm lens on a 35mm. While this crop factor is often called a focal length multiplier, it is important to note that there is no magnification benefit, only a smaller field of view. This means that, although it is possible to use lenses made for the 35mm format on APS-C cameras. However, lenses designed for 35mm may lack sufficient resolution to get the best from smaller formats.

Brand designations

Drawing showing the relative sizes of sensors used in most current digital cameras.

Most DSLR and third party lens manufacturers now make lenses specifically designed for APS-C cameras. The designations by brand include:

• Canon EF-S
• Nikon DX
• Pentax DA
• Konica Minolta DT
• Sony DT
• Sigma DC
• Samsung NX
• Tamron Di II
• Tokina DX

Multiplier factors

A crop factor (sometimes referred to as a "focal length multiplier", even though the actual focal length is the same) can be used to calculate the 35 mm equivalent focal length from the actual focal length. The most common multiplier ratios:

• 2.0× — Four Thirds system
• 1.7× — Sigma SD14, Sigma SD10, Sigma SD9, Canon EOS DCS 3^†
• 1.6× — Canon EOS 7D, 500D (T1i/X3)^†, 550D (T2i/X4), 600D (T3i/X5), 60D, 50D^†, 1000D, 1100D, 40D^†, 400D^†, 30D^†, 450D^†, 20Da^†, 350D^†, 20D^†, 300D^†, 10D^†, D60^†, D30^†
• 1.54× — Pentax K20D^†, Pentax K-7
• 1.53× — Pentax *istD^†, Pentax *istDs^†, Pentax *istDs2^†, Pentax *istDL^†, Pentax *istDL2^†, Pentax K100D^†, Pentax K100D Super^†, Pentax K10D^†, Pentax K200D^†
• 1.52× — all Nikon DSLR cameras except the full-frame D3, D3s, D3x and D700; all Fuji, Sony (except for the full-frame α 850, α 900), newer Pentax DSLRs (k-m, k-x and later models), and Konica Minolta DSLR cameras.
• 1.3×^‡ — Canon EOS-1D Mark IV^††, 1D Mark III^†, 1D Mark II^† (and Mark II N), EOS-1D^?, Kodak DCS 460^†, DCS 560^†, DCS 660^†, DCS 760^†, Leica M8, M8.2

Notes:

^†Discontinued

^††To be discontinued in March 2012.

^‡ A 1.3× Focal Length Multiplier is also known as APS-H. Actual multiplier factor is 1.28× for the Canon EOS-1D Mark III and 1.29× for the Canon EOS-1D Mark IV

APS-C lens formats

Canon, Nikon, Sony and Pentax have developed and designed lenses specifically for their cameras with a lens factor (more fully, lens focal length conversion factor) or "crop factor". APS-C cameras use a smaller area to form the image than traditional 35 mm cameras, and so lenses used on APS-C format cameras have a correspondingly narrower field of view. For example, a 28 mm lens is a wide angle lens on a traditional 35mm camera. But the same lens on an APS-C camera, with a lens factor of 1.6x (relative to a standard full-frame 35mm format camera), has the same angle of view as a 45 mm (28 mm x 1.6 lens factor) lens on a 35 mm camera—i.e. a normal lens. Several third-party lens manufacturers, such as Tamron, Tokina, and Sigma, also manufacture a range of lenses optimised for APS-C sensors.

Canon introduced the Canon EF-S line of lenses in 2003 alongside the 300D. These lenses place the rear of the lens closer to the camera's sensor (referred to as short back focus). This has several benefits, including lighter lenses and a narrower field of view (which implies “longer” zoom). EF-S lenses are compatible with Canon's APS-C digital SLRs, with the exception of the early Canon D30, Canon D60, and Canon 10D, which predated the introduction of the mounting system. EF-S lenses will not physically mount on Canon's full-frame digital or 35mm film SLRs.

Nikon has their DX format for their line of APS-C digital cameras. These can be mounted to the full-frame D3, D3x, and D700 models at the cost of fewer megapixels. These lenses generally exhibit vignetting when mounted on Nikon film bodies, but may be usable at longer focal lengths.

Sony has a DT line specifically designed for their APS-C cameras. These lenses can be mounted on any Sony Alpha, but are specifically designed for the a100-a700 series and the earlier Konica Minolta Dynax 5D and 7D. DT lenses can be mounted on an A850 or A900 in "crop" mode, where the frame is cropped and the resolution is halved.

Similarly Pentax produces the DA line for their APS-C cameras. These lenses are available in focal lengths that offer similar field-of-view as lenses previously available for 135 film. The trademark compact design of the DA limited series takes advantage of the smaller APS-C format. All DA lenses can be mounted on Pentax film bodies, albeit with increased vignetting. Only longer focal lengths in the rugged DA* series cover 35 film format fully.

See also

• Advanced Photo System
• Four Thirds System
• Lenses for SLR and DSLR cameras
• Crop factor

External links

• The Future of Digital — Full Frame or APS-C? written in 2004
• Focal length multiplier
• Digital crop explained
• Sensor size as a determinant of image quality