[quote name='hwyhobo' timestamp='1287131387' post='3638']
No, TC would not be just for academic exercise of comparing to another lens, but rather for practical purposes.
[/quote]
Hmm then why not also consider, say the Sigma 120-300 2.8 (OS?) + 1.4x? It's a really sharp lens. I've tested it against the Nikon 300 2.8 VR and the Canon 300 2.8 IS (i.e. some of the best lenses out there) and it stacks up really well.
[quote name='hwyhobo' timestamp='1287131387' post='3638']
Well, 2xTCIII has excellent opinion for quality.
[/quote]
Sure... it's probably the best quality TC out there... no doubt about that. But like Brightcolours said, all TCs do is prettymuch magnify the center portion of the primary lens. And all magnifications result in a loss of IQ (and light)... which happens even if the TC is perfect. So yeah...
[quote name='hwyhobo' timestamp='1287131387' post='3638']
Are you saying Nikon 70-200 f/2.8 II has poor IQ?
[/quote]
For me, yes... I've used it. It's sharp but it fringes up in bright light and has quite a bit of CA that reduces the clarity of the image that MTFs don't capture. Compare it to the Canon 70-200 2.8 IS II for example and you'll know what I mean. But the 200 f2 IS is better than anything [url="http://www.flickr.com/people/genotypewriter"]I've seen[/url] from Nikon <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='B)' />
And I did mean that all good primes are better than the best zooms in general. They have faster apertures, less distortion and most of the time less CA at equivalent apertures (CA "correction" doesn't bring back lost detail). But if you ask me, the thing that makes the biggest difference is the way most people use zooms <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='B)' /> Just IMO...
GTW
