kfoo Loc: Arkansas

I have a Nikon D7100. I had a friend of mine give me, he bought a Sony, an FX lens. What are the disadvantages of using the FX lens on a DX body.

CHG_CANON Loc: the Windy City

No disadvantages. Full-frame lenses will tend to be larger and heavier and more expensive, that's all.

kpmac Loc: Ragley, La

None, really.

kfoo Loc: Arkansas

What about he pixel on the DX body?

Quixdraw Loc: x

And, you get a bit more reach. I rarely use my DX lenses on DX cameras. Not a pixel peeper, but IMO the FX lenses are mostly better. There are some good DX ones, and to CC's point, they are generally smaller and lighter than FX glass.

User ID

A non-issue.

Keen

With Nikon, you can put most FX lenses on most DX bodies, or most DX lenses on most FX bodies. Doing either will effect the field of view. Whether it is worth doing is questionable. In some cases, it is worth doing, and in other cases it is not. Try it, and see if you like the results. If it gives you results you like, there is no disadvantage.

CHG_CANON Loc: the Windy City

Please don't present bad tangents or actual misinformation. The field of view of a lens on a DX body is exactly the same at the same focal lengths, whether the lens is a DX model or an FX model. This was the OP's question.

How a DX lens behaves on an FX body is a completely different question that only happens to have the same words in a different order.

rmorrison1116 Loc: Near Valley Forge, Pennsylvania

I use my Nikkor 28-300, which is a full frame lens, on my D7200 all the time with excellent results.

BebuLamar

You throw away half of the image formed by the lens which you paid for.

camerapapi Loc: Miami, Fl.

Actually I prefer a FX lens on a DX body but not the other way around. When using the FX lens on the DX body you will immediately notice that the focal length of the lens is not exactly what you see in the field of view of your camera. An example, if you fit a 24 mm FX lens to your DX body the so called "digital factor" makes it look when you look through your viewfinder like a 36 mm lens. The 24 mm focal length is still 24 mm but the digital factor makes it similar to the field of view of a 36 mm lens. You need a 16 mm FX lens to see the view of a 24 mm lens with your DX camera. Today many optical manufacturers make extreme DX wide angle lenses and Tokina comes to mind. Those lenses cover the whole DX sensor and are specifically made for the DX format.

A great advantage of using a FX tele lens with a DX body is that precisely because of the digital factor the field of view makes it look like a much larger tele than it is. Another example, fit a 200 mm FX lens in a DX body and your field of view now is 300 mm. It is not the same, unless you are close to your subject to shoot birds with a 200 than with a 300 mm field of view.

The FX lens covers the central part of the DX sensor so the corners of the lens are not taken into consideration meaning a sharper image.
I hope this helps you to understand the advantages of setting a FX lens in your DX body.

cameraf4 Loc: Delaware

One of the reasons I did not like DX cameras was, as a Landscape guy, I hated that my "extreme wide angle" 20mm lens only gave me images like a barely wide 30mm would on an FX body. You really do throw away a bunch of the lens viewing potential. A boon for Tele guys, sucks for WA guys like me.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

You will only be using the central part of the DX lens on your D7100 body. And that's the best part of any lens. Advantage FF lens on a DX body.

jerryc41 Loc: Catskill Mts of NY

Try a lens simulator.

https://www.sigma-imaging-uk.com/focal-length-simulator/
http://imaging.nikon.com/lineup/lens/simulator/
https://hisgallery.com/blog/collection-of-online-camera-simulators-lens-simulators
http://canonfeatures.ca/comparison-tool
https://www.diyphotography.net/use-nikons-lens-simulator-to-pick-your-next-lens-non-nikon-shooters-too/

SuperflyTNT Loc: Manassas VA

That’s a ridiculous statement.