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02-17-2012, 10:51 AM   #1
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Tamron Adaptall-2 SP 60-300mm and Pentax 1.7x TC

I assume there is no issue using the 1.7x with the 60-300mm, but has anyone tried this? I have the 60-300 at home in a different state so I cant look at it, but am I correct in assuming that the 1.7x would NOT add autofocus capability to it?

Any thoughts are welcome.

02-17-2012, 12:46 PM   #2
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You can attach the Pentax F1.7x AFA to any K mount lens to get 1.7x magnification but AF is only possible under bright to very bright conditions (midday) and if the subject is contrasty. I found f3.5 to be about the minimum aperture to achieve AF for normal contrast subjects, by f4.0 getting AF lock or AF confirmation iffy. Your 23A with f5.4 at 300mm and the F1.7x AFA, AF lock is mostly by chance.
02-17-2012, 01:52 PM   #3
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QuoteOriginally posted by millertime Quote
I assume there is no issue using the 1.7x with the 60-300mm, but has anyone tried this? I have the 60-300 at home in a different state so I cant look at it, but am I correct in assuming that the 1.7x would NOT add autofocus capability to it?

Any thoughts are welcome.
The pentax SMC-F 1.7x AF converter can make the lens auto focus within a focusing range once you manually focus close to the focus point, BUT I do not know if your lens is fast enough to reliably autofocus. The AF converter (by specification ) is designed for lenses with a maximum aperture of F2.8 but has been found by many users here to be reliable as long as maximum aperture is F4.0 or faster. There are some reports that it works and can achieve focus lock on F4.5 lenses, but I can advise it simply does not work with an F5.6 or slower lens.

Also, the TC will carry aperture data through if you have a KA mount for the lens, and will modify the aperçu values for the impact of the TC so that metering and p-TTL flash works reliably
02-17-2012, 02:15 PM   #4
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I've had some success with this combination

QuoteOriginally posted by millertime Quote
I assume there is no issue using the 1.7x with the 60-300mm, but has anyone tried this? I have the 60-300 at home in a different state so I cant look at it, but am I correct in assuming that the 1.7x would NOT add autofocus capability to it?

Any thoughts are welcome.
I have used this combination a few times, and want to do more, because it focuses very nicely with decent light with my K7. It is heavy for me, so I am better with it on a tripod with the Manfrotto lens holder for a tripod.

The first picture is with a tripod, pretty sure cable release, at 100%, the fine detail is still clear.

The aperture does not register on the first picture, on the next three it is f/6.7, I had the 60-300 wide open at f3.8.

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This cedar waxwing was handheld and still pretty sharp considering I am not too steady.

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These finches were taken through a window and hand held. The second one is a crop.

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I certainly think it can be usable and focuses pretty quickly, and though I'm not a tester, at least as fast as the 1.7 attached to my DA 55-300.

Hope this helps, Sharon


Last edited by Penmacgal; 02-17-2012 at 02:31 PM. Reason: Added aperture information
02-17-2012, 04:01 PM   #5
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Cool thanks for the replies.

@Penmacgal: Good to see your results, I would also be using it on a K-7, only in good lighting and on a monopod or tripod. I'll have to have it shipped out to me and keep my eye out for a 1.7x. Nice choice in bird feeders btw
02-17-2012, 07:51 PM   #6
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Your welcome

QuoteOriginally posted by millertime Quote
Cool thanks for the replies.

@Penmacgal: Good to see your results, I would also be using it on a K-7, only in good lighting and on a monopod or tripod. I'll have to have it shipped out to me and keep my eye out for a 1.7x. Nice choice in bird feeders btw
I'm hoping to use this combination tomorrow on a birding event, I do like the Tamron Adaptall 2 60-300mm.

BTW, don't know what I was thinking, those are song sparrows, not finches.

I wish that was my feeder! My friend has a nice glassed-in porch overlooking the feeder with plenty of shrubs and evergreens for cover. She gets some great photos.
10-22-2013, 03:48 AM   #7
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Would this be a case where the low-light focusing capabilities of K5ii and K5iis help? Or am I out to lunch here?
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