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11-09-2010, 05:18 PM   #16

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QuoteOriginally posted by Pentaxor Quote
as far as the Kenko 1.5 SHQ and and Tamron 1.4 PZ, both TC's support SDM/HSM
Did you actually try the TCs with SDM/HSM lenses? Or did you say that just because the TCs have the power contacts?

11-09-2010, 09:17 PM   #17
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QuoteOriginally posted by SOldBear Quote
Did you actually try the TCs with SDM/HSM lenses? Or did you say that just because the TCs have the power contacts?
I tried my copy and it works. I would think it has to do with the contacts. although there seems to be some conflict with others that theirs don't work.

but one thing is certain, the Sigma TC's have real issues with the P/K mount. this was verified to me by a lens rep. he said that Sigma is working on it and they might build a new version of TC's that would work well with SDM and most especially HSM. this made me decide to look for the Tamron.
11-09-2010, 11:20 PM   #18
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Do you really need a TC in the modern digital age? Consider that a 1.4 TC only gives you a 1.4 increase in focal length, but you lose 1 full stop of aperture, as well as degradation of the IQ from the lens, dimmer viewfinder, more difficulty in AF, etc. and it costs more money.

I think that for a great many applications, a 1.4 crop-zoom may be preferable to a TC, and you retain the f# of the original lens.

Consider this test. A photo was taken at a focal length of 144mm. Then at 200mm (a 1.4 mag) Compared the two.

Which of these pictures is the untouched 200mm and which is the crop-zoom of the 144 (to make it look like 200mm)? (No fair looking at EXIF)

Here are the 100% crops of the same images:

I haven't found a need for TC's since I used film.
11-10-2010, 05:51 AM   #19
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It's been noted in other posts, that none of the the teleconverters provide the camera with accurate focal length information. Given that sensor-shift SR requires this information to function correctly, one would expect Pentax to want to have this as a feature of any pro-spec teleconverter with their name on it.

I suspect that the SDM AF mechanism also uses focal length information, as my SDM lens hunts to and fro, past the focus point ad infinitum at very close shooting distances when coupled with a teleconverter with SDM/PZ contacts.

11-10-2010, 04:56 PM   #20
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QuoteOriginally posted by PentaxPoke Quote
Here are the 100% crops of the same images:
Top one is definitely sharper.

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