FX format (Nikon)

This is Nikon’s name for its full frame DSLRs, to distinguish them from its APS-C size ‘DX’ models. Most Nikon lenses are designed to fit this larger FX format. Those that don’t have ‘DX’ in the model name – though they can still be used on an FX Nikon in ‘DX crop’ mode.

Full frame sensor

This is a sensor the same size as the 35mm film negative, measuring 36 x 24mm. This is the most desirable camera type for most enthusiasts and pros, but full frame cameras are bigger, heavier and more expensive. Most DSLRs and mirrorless cameras use smaller APS-C sensors.

Effective focal length

The angle of view of a lens changes according to the size of the sensor in the camera. A smaller sensor captures a narrower angle of view and makes it look as if the lens has a longer focal length. So in addition to the actual focal length, the manufacturers will usually quote the ‘effective’ focal length too.

DX format (Nikon)

This is Nikon’s name for its APS-C format DSLRs. Some Nikon lenses are designed specifically for these smaller format models, and they include ‘DX’ in the lens name to signify that the can’t be used on the full frame models (well, they can, but only in a ‘DX crop’ mode.

Crop factor

Used to work out the effective focal length of lenses on cameras which don’t have full frame sensors. You multiply the actual focal length by the crop factor to get the effective focal length. The crop factor of an APS-C camera is 1.5, so a 50mm lens has an effective focal length of 75mm.

APS-H sensor

This is a relatively uncommon sensor size mid-way between APS-C and full frame. Canon used it for its EOS-1D high-speed pro sports/press photography DSLRs before these were merged with the introduction of the full frame EOS-1D X. Canon has since announced the development of a 250MP APS-H format sensor, though this has not yet been used in any commercial product. Sigma, meanwhile, has announced a new Sigma SD Quattro H mirrorless camera with a new APS-H format Foveon sensor. APS-H sensors measure approximately 30 x 20mm, or a couple of millimetres less.

APS-C sensor

This is the most common sensor size in cameras designed for enthusiasts and experts and it’s found in consumer DSLRs, mirrorless compact system cameras and some high-end compacts. APS-C sensors are around half the size of a full-frame sensor or the 35mm negative, and measure approximately 24 x 16mm. They have a crop factor of 1.5x, which means that you have to multiply the lens’s focal length by 1.5x to get its effective focal length in 35mm/full frame camera terms.

1.5-inch sensor

A unique sensor size used by Canon in its top PowerShot compact camera, the G1 X II. It’s just a little smaller than the APS-C format used by most DSLRs and larger than the 1-inch sensors used in other high-end PowerShot models, so it gets close to the quality of a good interchangeable lens camera.

1-inch sensor

A new sensor size roughly half way between the small sensors in point and shoot digital cameras and the much larger ones in digital SLRs and mirrorless cameras. It’s found in more advanced high-end compact cameras, and Nikon uses it for its Nikon 1 mirrorless cameras. It’s been adopted by a number of makers as a way of getting better image quality from compact (non interchangeable lens) cameras.