#PHOTO TIP – What is the difference between FX format and DX format?

One of the decisions that confronts photographers when buying a new camera is what format to choose.It can be very confusing as there does not seem to be any uniform sustem governing the way that formats are named, so it is tough to know exactly how to compare them.

For those buying a DSLR the choice is a bit simpler but the choices can still be bewildering.

Two of the most popular Nikon DSLR formats are FX  and DX. Other manufacturers use different names (Canon have EF and EF-S) but essentially FX is a Full Frame sensor (roughly equivalent to a 35mm film) and DX is a smaller sensor known as APS-C.

To help you understand the difference between them we have copied the information below from the Nikon support site.

The image area on the sensor differs between the FX and DX formats in terms of physical size. The FX format has an image area based on the 35mm (36 x 24) image circle, the image area of the DX format is approximately 24 x 16 mm.



 FX format sensor size approx. 36 x 24mm

 DX format sensor size 24 x 16mm


FX format
The larger FX image sensor is virtually the same size as the 35mm [135] film format which means that the focal length of a lens used on either format will be virtually the same. Many Nikkor auto focus and manual focus lenses can be used with FX format cameras. As Nikon has a long history of lens making there are restrictions and caveats to using some lenses which should be checked before making a decision to purchase. Click here for more information.

DX Nikkor lenses are engineered and optimised for use on both DX format and FX format digital SLR cameras. When mounted on an FX format digital SLR, the camera’s DX-Crop Mode is automatically engaged, altering the image capture area accordingly. This image crop is also reflected in the cameras viewfinder display with the image area not captured greyed out.


D3 viewfinder display (non-DX lens attached).

D3 viewfinder display (DX lens attached).


DX format
All lenses designated as DX type can be used with DX format digital SLR cameras. Many Nikkor lenses designed for FX or 35mm [135] film formats can also be used with DX format digital SLR cameras. The effect of using a Nikkor lens on a DX format camera will produce a magnification of the focal length of the lens by a factor of 1.5x (eg. a 50mm lens will produce the equivilant of a 75mm focal length). Click here for more information.


It is worth noting that the FX format is generally used in the top of the range professional cameras whilst the DX format is found in models that bridge the divide between professional and consumer models.

A larger sensor will generally mean a larger megapixel count and a more expensive camera.