Why is the TC-14 a "better" option? I can imagine that there is a slight difference in AF speed, but frankly I don't see a huge difference between my TC-14 and my TC-20 in that regard. Nor do I see a horrid degradation in quality. I just ordered, yesterday, a TC-17 so I will have a better idea next week when it arrives.
My 14 and 20 are the "original" models, not the II, but I would not expect that to make any difference at all.
I know that this has been widely debated over at Nikonians where the general consensus has been that the 1.4 has no discernible adverse effect (that is also my experience), the 1.7 is very acceptable, while the 2.0 noticeably degrades image quality.
All lenses I've used the 1.7TC on, including, the 70-200, have needed at least stopping down an additional 1.5 stops to get acceptable image quality. This means an f/2.8 optic (for quality results) becomes effectively 3 stops slower (1.5 from converter, 1.5 from the need to improve quality).
The 1.4 TC only needs 0.5 stops extra to give acceptable images.
I'm a little surprised why people want to use teleconverters on zoom lenses. Optically speaking this is not an optimal approach. A teleconverter is the once-in-a-while helper, not a permanent solution. If you find yourself having the TC always attached, you have the wrong focal length from the beginning. Simple as that.
Ken, thanks for the pointer to that other post. I have yet to see any definitive examples that point to the "problems" with these other TC's. One of the comments talks about the AF speed on the D70. I have both a D2H and a D70, and even with the TC-20 on the 70-200 on the D70 the AF is acceptable. Yes, it is slower than the bare lens as well as the TC-14, but it is not "disappointing". On the D2H, not a problem at all.
Bjorn, can you point to anywhere that shows comparison images of the three TC's, with explanations of what the "unacceptable" bits are? What is difficult for me is trying to see is what I am missing when I look at some of the images I shoot in this regard.
As to your question of why people would use TC's on the zoom lenses, for many I would think it is simply economics. I, for example, would love to have the 200-400 AFS-VR but budgetary constraints won't allow it. So I make do with a Sigma 120-300 f2.8 and my compliment of TC's. For exactly the same reason I own the Sigma 500mm f4.5 HSM.
I think that there is also quite a range when it comes to the word "acceptable", which is why I ask about examples. I know that I would learn a lot from seeing where the photographers such as yourself draw the "acceptable" line and it would certainly help me in both my understanding and working toward better images.
My test photo server currently stores some 600 GB of dull test chart pictures. There is no way I can upload even a small portion of this to a publicly available server and frankly I don't see the reason why either. What's acceptable to some is unacceptable to others, so we would only end up discussing semantics and splitting hairs. I'm not interested in such activities. Besides, since I do flush out data I might not even have the images available unless I go to my backup tapes.
Basically, lens testing is much more complex than people would think. You have to isolate the variables in a scientific sound approach. My experience with reporting such stuff in a decent manner to the general public on the Internet has been downright appalling. People demand simple answers and are annoyed when there is no such thing. Instead, they went their anger elsewhere and I 'm more than likely to get caught in the crossfire. So I have decided to take a break from lens testing, it's not that funny anyway and there are limits to the duration you can allocate to unpaid services.
Snapping some pictures with a hand-held rig isn't lens testing. It does not tell you anything that other people can evaluate or reproduce. When I do test with a lens, several hundred images are taken and the whole of them assessed afterwards. There is no "single" image that can tell "yes/no", "acceptable/unacceptable". Photography is not like that.
Bjorn, I agree with you that this is quite a complex issue, no doubt about that. I use your lens recommendation charts all the time, I have yet to find a case where I have any major disagreement by the way and thank you very much, especially for keeping them so up to date.
I can't speak for anyone else, but I tend to be a "visual learner" and as such a picture is truly worth a thousand words.
:lol: I'm sure that the brush the artist is using is not long enough, wide enough, or of the quality one would wish for, (it has less bristles than the best available). But apparently it does the job the artist wanted and so that is moot.
If a ever get a TC, I would get the 1.7 because if I am using it to get more reach for my 70-200VR (assuming I get rid of my 80-400VR) the 1.4 would not be enough for me, and based on the reports of many users, the 2.0 has issues. It all comes down to what you want it to do and how you will use it. For the occasional extra reach and convenience of a small TC rather than another lens the 1.7 would be my choice.
I have seen a number of photos where the 1.7 was used, and to my eye they looked fine. :lol:
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