Q. What is the difference between a Fx and a Dx lens on the two same types of camera bodies ? Will a Fx camera work on a Dx camera ? If yes, what are the points to be considered upon using this combination ? Also, entry level DSLRs like 5300 do not have focus motors. What is meant by this ? What lenses won't work with these models ? - A. Dear Varun, FX refers to Full frame Nikon DSLRs and DX refers to APS-C Nikon DSLRs. You can use any nikkor lens on any Nikon DSLR since the mount is the same. However, if you use a DX lens on an FX body, you will get an image area that is 1.5 times smaller as compared to a full frame image area. As for D5300, you can use any nikkor lens with the camera. But only AF-S lenses will auto focus with these cameras. If you are using and AF lens, you will have to focus manually.