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03-27-2010, 10:43 AM   #151
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This is a known bug. It only affects display so not really important.

03-27-2010, 10:44 AM   #152
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QuoteOriginally posted by lithos Quote
Perhaps the "A" in the "AF" in this product's name should stand for "Assisted" rather than "Auto."
Which is why, according to manual, it is supposed to be used with lens focussed on infinity. Is this written for performance issues or only for easier use, go figure.
Maybe just so they can write AF and not assisted, indeed.
03-29-2010, 05:14 PM   #153
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QuoteOriginally posted by cupic Quote
I think the 50mm f/1.4 will give you 85mm f/2.4,straight out multiplication
Wish I could dial that in with the aperture setting tho. :ugh:

I will add, as good as the 50/1.7 works with the 1.7x AF TC, the 50/1.4 works even better. I use shot of the Chrysler building, Met Life building [former Pan Am building] and Empire State Building, specifically the many antenna on them, to determine this. I haven't determined for sure, but the 50/1.4 + 1.7x AF TC may out resolve my Voigtlander 125/2.5; when stopped down of course. Voigtlander @ f/2.8 compared to the 50/1.4 * 1.7 @ f/2.8 goes to the Voigtlander.
04-14-2010, 11:41 PM   #154
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Would love a 1.2x (or lower AF TC

I picked up one of these in auction not too long ago. Was pretty much brand new, and I really need to use it more, judging by some of these fantastic photographs.

More controversially, I'd love to have a straight pass through TC where the sole purpose is to provide AF to Manual lenses without substantial Aperture penalty. Perhaps a Pentax F 1.2 or something. Would it still be a teleconverter if the magnification was 1x?

04-15-2010, 12:34 AM   #155
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QuoteOriginally posted by writeb Quote
More controversially, I'd love to have a straight pass through TC where the sole purpose is to provide AF to Manual lenses without substantial Aperture penalty. Perhaps a Pentax F 1.2 or something. Would it still be a teleconverter if the magnification was 1x?
I think an 1x converter would be a complicated beast: It would imply some kind of retrofocal design in order to compensate for the added distance to the film plane. Maybe even a 1.2x would be problematic.

But how about 1.4x? It still gives you only a modest aperture penalty: A 1.4x TC turns a 50 mm/1.7 into a 70 mm/2.4. That's not too bad - it could turn a M 50/1.7 into a "poor man's DA70"
04-15-2010, 03:06 AM   #156
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QuoteOriginally posted by gazonk Quote
But how about 1.4x? It still gives you only a modest aperture penalty: A 1.4x TC turns a 50 mm/1.7 into a 70 mm/2.4. That's not too bad - it could turn a M 50/1.7 into a "poor man's DA70"
It wouldn't be a "poor man's" solution. The DA70 may be cheaper than such an AF-adapter + 50mm lens.

I think, we should stop talking about the Pentax AF-adapter as being a 1.7x tc. That's only a byproduct and Pentax did not consider it to be a real tc. The smaller the magnification factor, the bigger the problems. Not only in terms of retrofocal design, but also in terms of correction for aberrations and, that's just a guess, also in terms of available AF throw. I would think, without calculating it, that the AF action gets more limited, the lower the magnification gets.

Ben
04-15-2010, 03:21 AM   #157
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QuoteOriginally posted by Ben_Edict Quote
I think, we should stop talking about the Pentax AF-adapter as being a 1.7x tc. That's only a byproduct and Pentax did not consider it to be a real tc.
I understand your point, Ben, but--regardless of Pentax's intentions--the multiplication factor is at least as significant a feature as the AF. In fact, For my purposes at least, it is more important. I don't understand how it could not be considered a TC (and a very good one.)
04-15-2010, 03:25 AM   #158
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QuoteOriginally posted by Ben_Edict Quote
It wouldn't be a "poor man's" solution. The DA70 may be cheaper than such an AF-adapter + 50mm lens.
Well, in Japan, the 1.7x TC costs less than half the price of the DA70, so if it was possible to make an 1.4x in the same price class (I share your doubts whether an AF 1.4x converter would be feasible), it would in fact be significantly cheaper to buy the TC + e.g. a used A-50mm 1.7. But implicit in my "poor man's" argument was also that you would use this TC for several lenses.

04-15-2010, 03:34 AM   #159
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QuoteOriginally posted by dadipentak Quote
I understand your point, Ben, but--regardless of Pentax's intentions--the multiplication factor is at least as significant a feature as the AF. In fact, For my purposes at least, it is more important. I don't understand how it could not be considered a TC (and a very good one.)
Yes, I don't understand that either. 1.4x and 1.7x teleconverters are interesting because they give a more useful max aperture than 2x (or more) converters.

I only own one TC, it's a Vivitar 2x that I bought at least 20 years ago which is so bad that I haven't shot a single really decent shot with it, made me think TCs are in general crap. But from all the praise for the Pentax 1.7x AF TC, I'm now considering if I shall try and get a new one from Japan.
04-15-2010, 04:04 AM   #160
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QuoteOriginally posted by dadipentak Quote
I understand your point, Ben, but--regardless of Pentax's intentions--the multiplication factor is at least as significant a feature as the AF. In fact, For my purposes at least, it is more important. I don't understand how it could not be considered a TC (and a very good one.)
Yes, I know it is probably more often used as a tc than as an AF-adapter. I have one myself, but hardly ever use it. The Pentax -L tele converters are simply stunningly good and my prefered choice for the two or three lenses, I use with a tc at all.

I would have prefered an AF-adapter with zero magnification and a real Pentax AF tc as a separate product. But that wish never came true…

Ben
04-21-2010, 03:13 PM   #161
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Here is my small comparision test,

Photo from left to right:

DA*300; DA*300 + 1.5X KENKO ; DA*300 + 1.7X AF PENTAX; DA*300 + 2X KENKO MC7

All at ISO400; 1/1250 sec f8 o corresponding

Crop 50% take from screenshot in lightroom



here is the link to the original photo
RapidShare: 1-CLICK Web hosting - Easy Filehosting ... i.zip.html

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