crop factor on full frame?

[madmardle]

There is a letter in this weeks AP from a Nikon user who is thinking about going full frame and wondering if his existing lenses are suitable. He has a 16-85 afs DX, another dx which I forget what it was, and a 70-300 FX. Their answer was that they would all be OK on a D600, but that the two DX models would still be subject to the 1.5 crop and the 70-300 would be fine as it is designated FX.
Am I missing something here? I thought that the 1.5 crop factor was to do with the smaller sensor size on DX bodies, and that that therefore DX lenses were not suitable on full frame models as they were not big enough to cover the sensor, or have I got it totally wrong.
I only ask as I too have a 16-85, a 35 1.8, and a 70-300, and I thought that only the latter would be ok if I could ever afford to go full frame.

 

[Cagey75]

There is a crop mode on the D600 & D800 that would allow DX lenses to work just fine. In FX mode you will get vignetting in the corners, but they are still usable. But, for FX, you really are best to use FX lenses.

 

[Moreorless]

As I understand it the actual coverage of DX lenses varies from lens to lens and thoughout the zoom range of certain lenses.

Doing a quick image search the 16-85mm on FX (without using the DX crop mode) would look like...

At 16mm...

At 85mm...

35mm 1.8 on FX...

 

[Nod]

A few years ago, shortly after I got my D700, I met up with Yv and had a play with her Sigma 10-20 on it. At 10mm, it threw this up

and at 20mm, the vignetting was much reduced (very similar to the 85mm shot above). I could have switched to Dx mode (which would reduce the D700 to fewer MP than my old Dx D70) but since I have a Sigma 12-24 (almost insanely wide on FF and so little distortion [perspective is very exagerated but ye cannae break the laws o' Physics!]) and a fisheye (Sigma 8mm) I didn't bother switching the frame size - the experiment was purely to see the amount of vignetting.

Not sure about your 35mm (if it's marked Dx, it'll vignette) but the 70-300 works very well on FF and the extra high ISO capabilities of FF sensored cameras reduces the impact the relative slowness (max aperture) has on shutter speeds.

IIRC, lenses to avoid on FF (as far as vignetting etc.) are marked Dx for Nikon lenses, DC for Sigmas, DiII for Tamrons and I think Tokina have nicked Nikon's Dx coding. All can be used on FF bodies but with vignetting (and a major loss of MP).

 

[madmardle]

OK Peeps,
Thanks for the replies, I didn't kmow that there were crop modes on the D600 etc.
Cheers,
Ken

 

[Nod]

Ken, if you have registered any of your kit (and possibly even if you haven't), you can download any Nikon manual from their website. Very handy for researching features on any future purchases and for seeing how easy (or hard!) it is to get at things you are going to want to.