Nikon "G" lense on a old film body

[Nisio]

just a quick question, I've a sigma 10-20 with no aperture ring and a nikon FM2 film body, I know that there's no apperture control if I mount X on Y but what would pictures be like if I was to do it?

Am I right thinking that the aperture would be something like f22 (or the lenses max)? I think the camera 's -/0/+ metering would still work?

[DaireQuinlan]

Originally Posted by Nisio

just a quick question, I've a sigma 10-20 with no aperture ring and a nikon FM2 film body, I know that there's no apperture control if I mount X on Y but what would pictures be like if I was to do it?

Am I right thinking that the aperture would be something like f22 (or the lenses max)? I think the camera 's -/0/+ metering would still work?

Yeah the shooting aperture will always be f/22 or whatever the min aperture is. The problem is that the camera has no way of knowing this, so your metering will be way off (by whatever the amount of stops between the min and max aperture of the lens is) because it'll meter wide open, and in the absence of an aperture indexing ring (the AI in AI and AIS) the camera will presume that its being SHOT wide open aswell. If you shoot manually and compensate for this you should be ok though, so long as your happy shooting at f/22 (imagine the depth of field !).

Another problem though is that I presume the 10-20 is designed for crop bodies, so you'll get at the very least heavy vignetting at the wide end, and more than likely just an image circle. It should work up around the 20mm mark though, but there's no guarantees.

[Nisio]

Thanks for that answer Daire. So if the meter has no information it assumes it's on f2.8 or equivalent? The 10-20 is for crop cameras alright there should be a fair bit of vignetting.

I'm going on a trip soon and might try get away with a nifty fifty on the film camera and the 10-20 on the digital camera, it'd be interesting to swap them around

[DaireQuinlan]

Originally Posted by Nisio

Thanks for that answer Daire. So if the meter has no information it assumes it's on f2.8 or equivalent? The 10-20 is for crop cameras alright there should be a fair bit of vignetting.

Effectively yeah. The AI and AIS Manual bodies rely on that little tab that gets pushed around the circumference of the lens mount to tell them how far down the aperture has been stopped. So they meter wide open and then apply the appropriate adjustment knowing that the aperture ring has been turned 3 stops or whatever. With the G lenses the little tab doesn't get moved around so the camera presumes that the lens is still wide open.

Actually, if the FM2 has DOF preview (I presume it does, my FE2 has it) then you can use it to stop down the lens and make a meter reading. I do this with an extension tube that I have that stops down the lens correctly, but doesn't have an AI follower tab, so it behaves a little like a G lens.

[Thirdfox]

It won't meter wide open if you take the metering after pressing the DOF preview button and hold the AEL.

That's how I shoot with my pre-AI lenses on my Nikon FE.

Though f22 and heavy vignetting isn't a great combination

[Nisio]

There's a DOF preview alright; I'll give it a try sure and see what happens (if I can find something that might look good with f22 and port-hole framing )

Thanks lads

[DaireQuinlan]

Originally Posted by Thirdfox

It won't meter wide open if you take the metering after pressing the DOF preview button and hold the AEL.

Yes, forgot that bit, that is indeed how I shoot with the tube attached in AE mode on every camera I own except for my F100 which is brilliant in every respect but one : for some unknown reason the metering switches off when you do a DOF preview so you can't use stop down metering. It's a weird quirk.

[Thirdfox]

Originally Posted by Nisio

There's a DOF preview alright; I'll give it a try sure and see what happens (if I can find something that might look good with f22 and port-hole framing )

Thanks lads

Remember to bring a tripod! ISO 200 and f/22 even in good sunlight will probably lead to 1/3 sec exposures.

The FM2 uses centre-weighted metering right? Otherwise your metering will be screwed up by the vignetting on the 10-20mm.

[Nisio]

Ya it's centre weighted metering; no space for the tripod probably, I have one of those small bean bag things that might help some.