This seemed like the best place to post this. Maybe I'm being really thick here (why change the habits of a lifetime) but I can't fathom this one out. I have an old manual focus Tamron 90mm f/2.5 adaptall, that I use on a number of film bodies, and also in stop down mode on a D700. Just recently I noticed it didn't stop down to f/32 with the Nikon adapter attached. After a bit of playing and thinking, I came to the conclusion that the stop down 'wheel' (not a pin like on most other old MF lenses) wasn't getting fully depressed, only reaching f/32. However, it went to f/32 when pushed with a finger. To check this out, I put the mearest skim of Araldite (a 2 part glue) on the adapter at the point where it meets the stop down wheel, and left it to set, to ensure the adapter pushes the wheel down far enough to engage f/32, and hey presto, problem solved. This may, or may not be associated with the actual problem which is this. The D700/90mm combo underexposes by about 1 stop. In stopdown mode the camera should choose an appropriate shutter speed for the manually set aperture to give a correct exposure, so it shouldn't matter what aperture is set, a correct exposure should be had (I've been using the uniform light brown of my decking steps to compare it with other lenses). I've checked it at similar focal length to 2 other modern AF lens that give correct exposures and it is about 1 stop underexposed regardless of the aperture set. I can get round it by setting +1 exposure compensation which presumably gives twice the shutter duration. To start with I thought maybe the aperture ring had got out of whack with the actual aperture and, say, when f/8 was set, the actual aperture was f/11. But that doesn't make sense as the camera doesn't care less what number is written on the lens barrel. In stop down mode it exposes correctly (or at least should do) for the size of the 'ole. Looking down the lens barrel, wide open at f/2.5 the aperture blades just dissapear into the body of the lens, as I would expect, so I don't think there is a problem with the aperture areas. So I tried it on a film camera with a different adaptall 2 adapter (M42) and it's fine. I feel like I'm asking a stoopid question that has a VERY obvious answer here, but I'm stumped. Enlighten me someone, please!