In reply to Fraser:
..
> If a lens is specifically for a cropped sensor camera, does it mean the focal length noted is 'as it says on the tin'? ie if it's a DX lens saying 55-300mm, is that what you 'really' get? I'd assumed it did, but I'm quite probably wrong.
They give you the real focal length of the lens. They have to, otherwise it would change name if you stuck it on a different format camera - which you can do with just about every lens.