Understanding DX sensors once and for all

As photography evolved and moved into the digital realm, the film was replaced by electronic chip known as an image sensor. A full frame digital SLR refers to a camera having an image sensor matching the 35mm format (36 mm x 24 mm). It is one of the widely used formats in digital photography. The other dominant format is APS-C  (approx: 25.1 mm x 16.7 mm).

All the major camera manufacturers including Canon and Nikon manufacture DSLR cameras with image sensors belonging to one of the formats mentioned above.

Simply put, a DX format sensor or lens simply means that it is made for an APS-C sized sensor.  It is Nikon's trademark for the APS-C sensor size.  

Some of the popular DX format camers include Nikon D3100, D7100 and D3300 among others. Any smaller sensor than 35mm format is known as a crop sensor (including DX). FX format cameras use the 35mm format and are known as full frame cameras.

Because of a smaller image sensor, a DX camera and lens system is able to capture a smaller area of image (as compare to an FX camera),  known as the crop factor. DX cameras have a crop factor of around 1.5. This means that a 24mm lens on a DX sensor camera will provide a 36mm (24 x 1.5 =36) view.

Read this post for more information on how a Nikon DX sensor differs from a full-frame FX sensor.

Advantages of having DX camera and lens system:

• A smaller image sensor means smaller camera body and therefore lighter in weight.
• The other major advantage is that such cameras are cheaper because they have a smaller chip size. All the lower end DSLRs by Nikon use the DX format.
• It is helpful for wildlife and sport photographers because it gives an instant 1.5x “zoom”.
• DX optimised lenses by Nikon are lighter and cheaper than FX lenses.

As always in life, all such benefits do come at a cost. Since the DX sensors have smaller size they have lesser light gathering capabilities therefore giving slightly poorer image quality and tonal range. They also exhibit high noise especially at higher ISO and poorer light sensitivity. That is the reason why pro grade photographers who are obsessed with image quality prefer using these full frame systems. Moreover FX lenses are fully compatible with DX bodies but not vice versa.

The world of photography is full of confusing terms and effective/equivalent  focal length is one of them. It's birth is due to DX and other cropped lenses. As discussed earlier, 24mm focal length on a DX lens will be equivalent to 36mm on a full frame lens. This conversion to full frame focal length is called as equivalent focal length. This can be useful when you are buying a lens for your DX camera.

For example, 50mm is considered as the best focal length to capture portraits and do street photography. But that focal length is with respect to a full frame body. The equivalent focal length of a 50mm lens on a DX body will be around 80mm.

For photographers on budget or those who will publish their work only on the web a DX sensor camera should suffice. Obviously if you want the best image quality FX camera is the way to go. But remember that even your subsequent investments in lenses will cost you comparatively more.

I hope this article has eliminated any doubts regarding DX sensors once and for all! Please share your thoughts in the comment section below.