Quote Originally Posted by 2F/2F View Post
They are two different birds built to acheive two different aims.

A teleconverter magnifies the image, but actually reduces close focusing ability. They are used to decrease the angle of view; usually of a lens that is already at least a medium-long lens. They are not made for close-up photography. They contain optics. Infinity focus is maintained.

I have only screwed around with dipoters; never taken a pic with them, so I am not sure if they cut light to a notable degree or not, but I don't think that they do.
Dear 2F/2F,

Thanks for contributing.

As I understand it, the teleconverter retains the original minimum focus distance of the lens to which it is attached and magnifies the image: the net effect is an enlargement similar to that obtained by an extension tube of the same length as the teleconverter, but without loss of working distance. Whether the image quality is the same for both appears to be a moot point. Both result in light loss.

As far as I know, a diopter lens has the advantage of no light loss.