the F3, M and FE came out about the time Nikon switched ti AI so ikon put a small chrome button near the little index tab that when pressed lets you lift the tab out of the way. This lets you mount a non AI lens without damage but the meter will not work. Hope this helps
You can mount non-AI lenses on the F3. And as you pointed out, you will need to lift the tiny "flap" on just above the mount. To meter, you will need to stop down.
As you face the camera without a lens and looking at it directly into the lens mount, the little lever that flips up is at the 1 O' Clock position.
To lift the little lever, you need to push down the little button, which is directly to the right of the little lever along the curve of the lens mount in. About 10mm further around the lens mount housing curve.
To close the lever to the normal down position, just push the lever down.
As I understand it, the F3 is capable of mounting any Nikkor SLR lens from 1959 onwards.
Yep, use it all the time. My F3 is my only camera to carry, when I need my 24mm (non AI), my 50 AIS, my 105 (again non-ai) and my 70-300 ED. It largely depends on what assortment of lenses you have, but the F3 has a superb meter for non-AI, up to the newest lenses..
Someone mentioned the F3's meter won't work with non AI lenses. I thought it would meter, but you have to use stop down metering with non AI lenses. And I also second John White's work. He converted 2 lenses for me and did a great job.
Someone mentioned the F3's meter won't work with non AI lenses. I thought it would meter, but you have to use stop down metering with non AI lenses. And I also second John White's work. He converted 2 lenses for me and did a great job.