Pegasus Loc: Texas Gulf Coast

Yet the DX 35mm lens also has ED glass and its filter size is similar to the FX 35mm f2.0 at 52mm. Makes you wonder why the DX lens has such a large objective lens when so much is not used by the DX format and it's not the "sweet part of the lens."

lamiaceae Loc: San Luis Obispo County, CA

If you are getting it as a gift (free) who cares if it Auto-Focuses on a D3100 or not. If you get a DX D5100 or higher or any FX you should then have full functions with the gift lens (unless they mean a ancient "film" lens, and I believe those can be modified to mount safely).

RickL Loc: Vail, Az

Fx af film lenses need no modification and fit the d7xxx, d750 and the dxxx. These camera all have motors and operate these lenses well

The D810 takes the dx lenses at 24 mp

rehess Loc: South Bend, Indiana, USA

I moved from Canon to Pentax two years ago, but one thing I'll say for Canon is "if it mounts, it works" {and you can answer the if it mounts" part by determining once what mounts your camera provides}.

DavidPine Loc: Fredericksburg, TX

I only use FX lenses on my D500. Quality is outstanding.

jamesl Loc: Pennsylvania

I have 2 FX lenses at this time that I use on my D3100. They are a Nikon 50 mm and a Sigma 70-300 mm and they work fine except that they only work in manual focus since the D3100 doesn't have a focus motor built into the body. When I use them on my D7100 the auto focus works fine since the D7100 has the focus motor in it. If you don't mind manual focus you should be fine.

Jeffcs Loc: Myrtle Beach South Carolina

You are correct in above when the crop factor come into play is when the image is printed FF to DX into say a 4X5 size or the 4X5 is to FF as something closer to 3X4 on a DX so to make equal size prints from a DX body is where the angle of view and crop factor of 1.5

rgfulton

Wrong, the f number of a lens is a function of the aperture diameter and focal length, not the "effective" focal length.

whwiden

I like to use a 28mm pancake lens from Voigtlander on a DX body for general street photography. It gives about a 42mm equivalent angle of view--almost perfect for a normal lens.

rgfulton

And you experience no edge/corner image degradation? Sounds like a well designed (perhaps over-designed) lens!

whitewolfowner

They work great; you are using the center of the lens and most FX lenses will out perform any DX lens in the Nikon line.

RWR Loc: La Mesa, CA

Only the barrel diameter is the same. I have an 85mm FX Nikkor and an 85mm DX Nikkor - both take 52mm filters but the DX front element diameter is about 20mm less.

Diamond41 Loc: St. Louis, MO

I have D3300 and FX lenses fit but do not play well. I will keep my lenses and will upgrade to something to handle them, perhaps a 750 or 810.

Bunkershot Loc: Central Florida

Go for it. I have a D7100 and have been accumulating fx lenses. I now have a 10-20, a 24-70 and a 105 macro. All of them function superbly with the dx sensor.

Pegasus Loc: Texas Gulf Coast

I'm a little confused here so maybe you can help me out. Are you actually comparing an 85mm f/1.4 FX lens or an 85mm f/1.8 FX lens to an 85mm f/3.5 DX lens and then saying that the objective lens on the DX lens is smaller because the DX format doesn't need as big an objective lens as an FX lens?

See, the reason I'm confused is that I always thought that focal length is focal length, irrespective of the sensor format and that it was the same for the f-number. I also thought that a bigger objective lens for the same focal length affected the f-number, not the magnification or field of view. By your statement you invalidated these beliefs.

I see four 85mm prime lenses at the Nikon website, three are FX lenses, an f/1.4, an f/1.8 and a Micro lens. I'll discard the micro lens for now. The fourth 85mm lens if an f/3.5 DX lens. The f/1.4 has a filter size of 77mm. The f/1.8 has a filter size of 67 and only the f/3.5 DX lens has a filter size of 52mm, so, I'm not sure what 85mm FX lens you have but if its filter size is 52mm, then if going to be f/2 or slower and it's not listed at the Nikon site. Maybe it's an old lens.

I hope you can help me understand your point of view.

ETA: My calculations show that the objective lens diameter for the three lenses are as follow: f/1.4: 61mm; f/1.8: 47mm; f/3.5mm: 24mm.

ETA 2: I found a reference to an old 85mm f/2 lens with a 52mm filter size produced in the 1970. Maybe that's the one you're talking about. Its objective lens diameter would be 43mm.