Quote:
Originally Posted by bojan
No need for stacking, tele-extender (as well as barlow) will have larger magnification if distance to camera is longer.
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Hi Bojan,
That's true for a Barlow (typically using a negative doublet lens) but, not true for a telecentric amplifier (teleconverter, telextender or powermate) which typically use a negative doublet and positive doublet in concert. With a true Barlow (negative doublet) the light rays diverge coming out and hence the possibility of adjusting magnification with position. With a telecentric amplifier device( teleconverter, power mate, etc..) the light rays are parallel out and the magnification is fixed by the focal length ratio of the negative and positive doublets it contains.
I can't imagine one would want to use a Barlow with a camera lens (and camera) when it so easy and back registration distances are easily controlled by design of the normal teleconverter device. Just click them together. But, like anything, there's no free lunch and image quality and light will be reduced compared with a prime focus optic of equivalent focal length,( depending on the quality of that optic of course)
Best
JA