FX and DX Format Cameras

Nikon makes DSLR and Z Series cameras with two different sensor sizes known as FX format and DX format. 

FX format cameras have an image sensor that measures approximately 36mm x 24mm. This is also known as a full-frame format as the sensor is the same size as a traditional 35mm still image frame. The size of the FX sensor offers higher sensitivity and lower noise. 

A DX sensor is 2/3rd the size of an FX sensor and measures 24mm by 16mm. The DX sensor allows the production of lighter and smaller cameras that still have very high image quality.

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Nikon lenses are designed to work on both image formats but DX format lenses are optimised to work on DX format cameras and have a “DX” mark on the lens. DX and FX lenses can be used interchangeably on both cameras but the lenses angle of view changes depending on the camera format.

Lenses are round and they project a round image onto the camera image sensor. The image circle of an FX lens is designed to match the size of the FX sensor. Since the FX sensor is rectangular in shape, the resulting image is also rectangular.

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For example, that means a 24mm FX lens will give you a 24mm FX angle of view as you would expect. 

Using an FX format lens with a DX format camera

An FX lens image circle when projected on a DX sensor crops the image by about 1/3rd. This crop has the same effect as magnifying the image by approximately 1.5x. This means that a 24mm FX lens on a DX format camera will give you the equivalent angle of view of a 36mm lens on an FX camera. This is called a 1.5x crop factor.

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Using a DX format lens with a FX format camera

With this combination the DX image circle is actually smaller than the full frame sensor. 

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Nikon FX cameras automatically compensate for this by only activating the pixels matching the DX sensor size. This is called Auto DX crop.

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Benefits of using FX and DX formats

Most NIKKOR lenses can be used on both DX and FX cameras. If you are considering upgrading from a DX camera to the larger full frame FX camera, then you can continue to use your existing DX NIKKOR lenses and the FX camera will automatically compensate for the smaller image circle using Auto DX crop. If you then purchase a full frame NIKKOR lens for the FX camera, the lens can still be attached to your DX camera and the image will appear magnified 1.5x. 

FX and DX format cameras offer the option to select different Image areas from the Shooting menu. Setting different options for the image area allow you to shoot in different area crop modes, options vary between cameras.

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