DX & FX lenses

480sparky

Senior Member
DX lenses are marked right on them as such.

The physical difference is the size of the image circle projected onto the sensor. DX lenses need only to project a circle large enough for a DX sensor. FX lenses project larger circles for covering the larger FX sensors.
 

Dangerspouse

Senior Member
Hi arshuter -

Basically, DX and FX cameras have different sensor sizes so they need lenses which will spread light across the correct area of each. You can mount FX lenses on a DX body and vice-versa, but there will be considerations that must be taken into account (most FX cameras automatically sense if you mounted a DX on it and adjust, but DX cameras don't do that if you stick an FX on, I believe). Your D7100 has a DX sensor (the smaller of the two sensors).

You can tell which lens is which by looking at the lens itself. Either "DX" or "FX" will be printed on the model nomenclature.

Check out these from the Nikon site itself. They're quick, and should answer any questions you have:

https://www.nikonusa.com/en/learn-and-explore/a/products-and-innovation/the-dx-and-fx-formats.html

https://www.nikonusa.com/en/learn-and-explore/a/products-and-innovation/dx-nikkor-lenses.html

Hope this helps!

:)
 
Top