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10-21-2009, 08:30 AM   #16
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QuoteOriginally posted by Spock Quote
You misunderstood me - I wasn't referring to AF - I thought it was strange that apparently the only TC that modifies the aperture information is the Pentax AFA 1.7X. If that is the case, I asked, what purpose do the electrical contacts have on the A-series converters?
Simply, to lead the lens' signals through.

Ben

10-21-2009, 08:41 AM   #17
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QuoteOriginally posted by Ben_Edict Quote
Simply, to lead the lens' signals through.

Ben
Seems a bit pointless if it will report an incorrect f-stop value to the camera.
10-21-2009, 03:29 PM   #18
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QuoteOriginally posted by Spock Quote
Seems a bit pointless if it will report an incorrect f-stop value to the camera.
It may seem pointless, but is a simple fact - not my invention. You should not forget, that these tcs are very old and microprocessors were not really en vogue for such small and comparably "low-cost" applications at the time of their release into the market. And up to today Pentax has not released a newer tc.

Ben

Last edited by Ben_Edict; 10-22-2009 at 04:25 AM.
10-22-2009, 03:51 AM   #19
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So what's the verdict on the pro-optic teleconverter? Worth getting?

10-22-2009, 04:32 AM   #20
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QuoteOriginally posted by Spock Quote
So what's the verdict on the pro-optic teleconverter? Worth getting?
Not easy to say. I wouldn't buy it, as experience shows, that image degradation with 2x converters is visible, where generally 1.4x tcs provide very high IQ. Nevertheless, if I need a 2x tc, this experience is worth next to nothing. You could alternatively (if you don't need AF sipport) have a look into the forum's for sale area, for instance here:
https://www.pentaxforums.com/forums/photographers-marketplace/77228-sale-85mm...converter.html

The original Pentax A 2x-S modell is among the best available in PKA mount, only topped by the 2x-L modell - which might not fit your lenses.

Whether this tc is worth the money is also a question of the lenses you intend to use with it. If the lens is optcally perfect, the loss introduiced by the tc might be acceptable. If the lens is mediocre, the IQ loss might not be tolerable. So, for instance I wouldn't use this tc with a slow zoom lens (indeed I never use a tc with such a lens).

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10-22-2009, 08:49 PM   #21
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QuoteOriginally posted by Ben_Edict Quote
Not easy to say. I wouldn't buy it, as experience shows, that image degradation with 2x converters is visible, where generally 1.4x tcs provide very high IQ.
? This TC is a 1.4x.
10-23-2009, 03:09 AM   #22
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QuoteOriginally posted by Spock Quote
? This TC is a 1.4x.
You are right, I am sorry. Through the length of this discussion, I lost track. Nevertheless I wouldn't buy it. For not much more you could find a Tamron 1.4x or the Kenko 1.5x, which are well-proven products or get a second hand Pentax A tc, which would loose AF, but give very good optical performance. But that would be my personal decision and somebody else sure has his own preferences.

If I remember rightly there have been several in-depth discussion threads during the last 6 to 9 months about tcs and I think, the same arguments have been repeated again and again by all the contributors.

Ben
10-23-2009, 03:34 AM   #23
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QuoteOriginally posted by Ben_Edict Quote
I wouldn't buy it. For not much more you could find a Tamron 1.4x or the Kenko 1.5x, which are well-proven products or get a second hand Pentax A tc, which would loose AF, but give very good optical performance.
Thanks Ben. Good advice.

10-23-2009, 04:29 PM   #24
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Talking to one of the guys from one of the top UK Pentax dealers (SRS Microsystems), a lot of these t/cs are actually made in the same factory and simply badged differently. He mentioned Tamron, Kalimar and some Kenko. I have the Tamron 1.4 and looking at tha photo in the OP's link, it is identical - seven contacts, even down to the knurling on the body and release lever. They are supposed to with with lenses of F4 or faster. I have found that it takes 2-5 attempts to focus and the image quality is reduced that a picture taken with my DA*300 on the t/c will not be as good as one taken with my Sigma 150-500.
10-24-2009, 03:54 AM   #25
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QuoteOriginally posted by Oggy Quote
Talking to one of the guys from one of the top UK Pentax dealers (SRS Microsystems), a lot of these t/cs are actually made in the same factory and simply badged differently. He mentioned Tamron, Kalimar and some Kenko. I have the Tamron 1.4 and looking at tha photo in the OP's link, it is identical - seven contacts, even down to the knurling on the body and release lever. They are supposed to with with lenses of F4 or faster. I have found that it takes 2-5 attempts to focus and the image quality is reduced that a picture taken with my DA*300 on the t/c will not be as good as one taken with my Sigma 150-500.
Your information, that many tcs come from the same facory and are just rebadged is ofcourse true and well-known. Just look at those current lenses you'll get from Vivitar, Phoenix, Samyang etc. (made by Samyang).
But not all tcs come frome the same one source. Tamron, it seems, makes its own 1.4x tc, though it is very similar to the Kenko version. That they all sport the same contacts is ofcourse a necessity, as these are the Pentax A and power zoom (sometimes working as SDM contacts) contacts... That the outer appearance resembles the well-aclaimed Tamron modell is in all probabilty not a coincidence, but a feature to profit from the Tamron's merrits.

Your DA 300 is probably among the sharpest lenses for Pentax today and it is no surprise, that a tc will degrade its IQ.

Ben
10-24-2009, 01:44 PM   #26
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Hi Ben

Using a T/C will always degrade image quality regardless of the lens. My point was that it degrades it to the extent that I would be better off if I need that length, digging out the150-500. Given that the T/C makes the AF very unreliable (which I rely on heavilly as my eyes are not great), I hardly ever use mine.
10-24-2009, 01:58 PM   #27
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QuoteOriginally posted by Oggy Quote
Hi Ben

Using a T/C will always degrade image quality regardless of the lens. My point was that it degrades it to the extent that I would be better off if I need that length, digging out the150-500. Given that the T/C makes the AF very unreliable (which I rely on heavilly as my eyes are not great), I hardly ever use mine.
Of course any tc will degradade IQ. I think we all know this. If AF becomes unrealiable, I think the lens was unsuitable for a tc to start with. Under unsuitable lenses I would generally count any consumer grade zoom lens (all are too slow for tc use) etc.

Nevertheless, some lenses and tc combinations are good or even excellent matches. For instance the older (non-HSM) Sigma 70-200/2.8 is stunning with the Sigma Apo 1.4x tc and still very sharp with the Sigma Apo 2x tc. The same is true for any prime tele photo lens which can be used with the Pentax A 1.4x-L tc or even the 2x-L version. In these rare cases (there are more, but I only refer to equipment I really use, not something I just read aboiut somewhere), a tc can be used effectively and with great results.

It is always a matter of the whether the lens/tc-combination works or not.

Ben
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