So, I have a Nikon D40 and my cousin gave me his old sigma lens. He's a professional photographer and he moved from nikon to canon. This lens is a Sigma 70-210mm f3,5-4,5 APO Macro. The lens has manual aperture selection and the only way my camera recognize it is when I set the lens to f22. Thats because the aperture selection ring has a projection that presses a "lever" on my camera, and this way, the D40 recognize the lens. Here's a link with a picture of the lens: http://www.sigmauser.co.uk/images/stories/museum/199470210APOMacro.htm It's almost the same as mine, but mine doesn't have the autofocus inscriptions, although I think it can handle autofocus. I was wondering if this lens would fit for me while having the D40. I mean, I can only take photos in F22. So I would be a little restricted here. I have plans to buy a new camera, but I don't see that happening in short time. Maybe in 3 years. And I don't know if this lens will fit a modern camera either. So my question is, do I keep this lens? Or should I sell it? Is it possible that this lens would fit another camera, a new one, or just old models? Older than my D40. Thanks.