APS-C vs FULL-FRAME

THE CROP FACTOR

Digital SLRs have either a full-frame

sensor – so called because it matches the size of 35mm film – or an APS-C format sensor, which is slightly smaller (36 x 24mm vs 23.6 x 15.7mm). APS-C-based SLRs are also known as crop-sensor cameras. This is because the APS-C sensor only captures the centre portion of the frame seen by the lens, just as if the full-frame image had been cropped afterwards. In terms of the amount that is cropped, it varies slightly between models – Nikon APS-C sensors zoom to 1.5x compared to full-frame, and Canons zoom to 1.6x.

FULL-FRAME TERMINOLOGY (NIKON & CA NON)

Nikon’s range of full-frame camera bodies and lenses are called FX, and

the crop-sensor range is DX. FX lenses can be used on DX bodies, but DX lenses shouldn’t really be used on full-frame bodies due to vignetting. Canon crop-sensor lenses are known as EF-S and full-frame as EF, and the same principles apply – in fact, EF-S lenses can’t even be mounted on

EF full-frame bodies.

CHANGING VIEW POINTS

Focal length numbers can be confusing, especially when you factor in the sensor size. Place a 50mm lens on a full frame camera

and the angle of view will be a traditional 50mm view - a spread of around 40 degrees. But put the same 50mm lens on a DSLR with an APS-C sized sensor and the angle of view will tighten to around 26 degrees, comparable to a 75mm focal length

on a full-frame body.

SENSORS AND DEPTH OF FIELD

As well as the angle of view, sensor size also has a bearing on depth of field. The larger the sensor size, the

less depth of field. This is why cameras with small sensors, such as smartphones, find it harder to produce a shallow depth of field, and perform poorly in low light. And it’s also why large-format 5 x 4 cameras need apertures that stop down to f/64 for front-to-back sharpness.