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Old Aug 9, 2010, 10:27 AM   #11
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Old Aug 9, 2010, 10:57 AM   #12
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Old Aug 9, 2010, 11:27 AM   #13
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Old Aug 9, 2010, 9:27 PM   #14
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So now I just had to go out and research this again ! It seems that it's the Tamron-F Pz-AF MC4 1.4x TC which supports SDM, this is a Q&A from the poster on another site that was discussing it :

So if I understand correctly - The Tamron AF 1.4 works with the SDM? It removes NO function from the lens?
Yes, everything works perfectly...It was and is a pleasant surprise...


He was using a K100D super with the 18-250 tamron lens, sigma 70-300apo, bigma 50-500, Sigma 135-400, 50mm F/1.4 & DA*50-135.

It is not a Pentax x1.7 for sure, but a very reasonable range extension for a very reasonable price (in comparison to the Pentax). I will still be looking out for the Pentax but it does seem to be a good alternative if you come across one.
Hi Kevin,

I think you just single handedly doubled the responses to this thread. .

I have a Tamron 1.4x PZ AF MC4 TC, it was actually one of the first "lenses" I bought after I got my DS -- the first of my Pentax DSLR bodies.

My statement about the Tamron not being an AF adapter was in reference to your post that seemed to imply that there was a Tamron TC out there that added AF capability to MF lenses. AFAiK, there is no such animal. The Pentax F 1.7x AFA is the only practical one that does this. There is a distinction between an AF TC and an Auto Focusing Adapter. The former allows an AF lens to pass through AF information, and auto focus. The latter has moving elements within the AFA that does the focusing, so it adds AF capability to any lens (and actually disables the autofocusing capabilities of AF lenses and treats them the same as if they were MF only).

As far as supporting SDM, The PZ versions of the Tamron 1.4x and the Kenko 1.5x have the PZ contacts that SDM/HSM lenses use, but as the "PZ" designation shows, these contacts were designed for use with Power Zoom lenses, and not necessarily for SDM/HSM in-lens focusing motors, though the contacts are seemingly the same. In fact, both of these TCs were officially discontinued soon after the first SDM lenses were out on the shelves, and neither Tamron nor Kenko ever claimed that they were actually compatible with the new in-lens motor focusing system.

It's interesting that the user that you quote "was using a K100D super with the 18-250 tamron lens, sigma 70-300apo, bigma 50-500, Sigma 135-400, 50mm F/1.4 & DA*50-135" has this particular stable of lenses.

The Tamron 180-250 is an f3.5-6.3 max aperture lens, and with a 1.4x TC, it's max Av would become f8.8 at 250mm. I have the Pentax version of this lens, and even in bright sunlight, AF is hit-and miss --mostly miss. I can occasionally get a focus lock, but lock to lock hunts are much more likely. I don't consider this acceptable performance, and never use this lens with a TC expecting to use AF.

I don't have a Sigma 70-300, but I do have an older model Tamron 70-300/4-5.6 which many consider to be a close equivalent with the same max Av range, and with the Tamron 1.4x, the max Av becomes f8 at 300mm. This combo locks AF more readily than the 18-250, but it's far from a reliable AF performer. For my use, I need AF that locks quickly and reliably at least 90% of the time. The 70-300+1.4x does not come close to this, nor does the Pentax 80-320/4-5.6+1.4x TC combo.

I don't have the Sigma 135-400/4.5-5.6, but I again have a pretty equivalent performing lens, the Tokina 80-400/4.5-5.6. Again we have a combo with f8 as the max aperture with a 1.4x TC, and again, the AF performance is spotty at best, and much worse than the lens alone.

I think that this can also be said of the Bigma at f6.3 at 500mm, perhaps Dawg, Trojansoc, or another Bigma owner can comment on this more definitively. . .

The F or FA50/1.4 will definitely AF fine with the Tamron 1.4x AF TC.

I also have the DA*50-135, and with my Tamron 1.4x AF TC, the SDM motor works, the lens tries to focus, but it will not attain a lock unless the lens is prefocused to very close to perfect focus. I find this unacceptable, but I've heard of other users who apparently find this as usable, and claim that the PZ TCs are "SDM compatible". I can't make this claim with any conviction.

It must be said that outdoor lighting conditions vary considerably according to location, and mine -- in the northern part of the temperate zone might color my view of AF performance compared to someone who lives much closer to the equator. I've noticed a significant difference in light intensity at noon between early spring and the middle of June here around Chicago.

I have my doubts about the quoted user's credibility concerning TC use. . .he/she does not have a lens lineup that inspires confidence on this subject.

For me, for a TC to be considered practical for AF, the combo must function at least close to as well as the lens alone. In other words, apart from the magnification, the IQ and focusing speed should be essentially transparent, with neither taking a significant hit in performance with a high quality, appropriately fast lens.

The AFA gets a pass for the prefocusing requirement with tele lenses since it adds AF speed and the short focusing range is actually a useful limitation (focus limiters are a sought-after feature on a lot of high end dedicated macros and ultra tele lenses). The limited range also allows it to be used with somewhat slower lenses since the prefocusing drill gives the AF system more contrast for the AF system to work with than a lens that's totally out of focus will.

The Tamron 1.4x and Kenko 1.5x, in addition to the Sigma 1.4x (with the limitations to its compatibility due to the protruding front element) are all good TCs, and are certainly useful. I have the Tamron and an earlier Sigma, and always have them in my bag. The P F 1.7x AFA is just uniquely useful to me, and is by far my favorite.

Scott
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Old Aug 9, 2010, 10:14 PM   #15
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Scott sorry to be so late posting but I have been away from the site for a couple of days. I love this series of shots.

In spite of the heat you had a fine day shooting. Nice capture of the hawk.

Your work with the 510mm FL combination on these subjects was outstanding. I assume you were hand holding the camera.

I tried to get a shot the other day of a Hummingbird Moth and it was flitting so fast I could not get a focus on it with my Viv 105.

Nice Job!

Lou
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Old Aug 9, 2010, 10:35 PM   #16
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Scott,

Oh, sorry about that ! Shanghai is experiencing chronic problems with internet signals for the last month or so and often I have to refresh the page (after disconnecting / reconnecting) and repost - guess sometimes the post had already gone through even though it didn't show up here !

I'm amazed - you are a walking encyclopedia ! Fantastic write-up, I've clipped that and stored it with my other clippings for future reference. Thank you very much for taking the time to write that, I've learnt a lot.

The poster on another dedicated Pentax forum (I think you can guess which one) put up quite a few shots from his combos and they did seem sharp, he commented on which ones were hunting excessively and which ones weren't, for most of them if I remember correctly. Not all the shots are still there as the thread is over a year old.

I think I'm going to switch my attention to the AFA !

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Old Aug 9, 2010, 10:48 PM   #17
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Scott sorry to be so late posting but I have been away from the site for a couple of days. I love this series of shots.

In spite of the heat you had a fine day shooting. Nice capture of the hawk.

Your work with the 510mm FL combination on these subjects was outstanding. I assume you were hand holding the camera.

I tried to get a shot the other day of a Hummingbird Moth and it was flitting so fast I could not get a focus on it with my Viv 105.

Nice Job!
Hi Lou,

Thanks!

No need to apologize, I've been pretty remiss about posting comments for the last couple of months at least. The weather, over abundant foliage from the above average rains, and the decreased maintenance budgets and efforts at the forest preserves and parks in the area plus some actual anti-bird measures at some of my usual haunts have made it hard for me to go out shooting, so photography has taken something of a back seat for me lately. At the hospital pond where I've shot GBH, Egrets, Gulls, Caspian Terns, and Killdeer, they actually strung line at 10 foot intervals across the pond to discourage the birds. I wrote a letter to the hospital administrator, but got no response. I've entertained a covert mission with black face and some wire cutters, but I decided that I can't really afford to be much of an activist at my age. . .

The hummingbird moths are a continuing project for me. I've only seen two close enough that I might have a shot at them, and I'm always on the lookout. You're right about the flitting -- they never seem to stop, and they're very tough to shoot. I only got a few shots of this guy, and this one was the only one that was close to acceptable from either motion blur or misfocus.

All the shots were handheld. I decided to do more of this at the beginning of the season.

Scott
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Old Aug 11, 2010, 6:26 PM   #18
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Another late poster - been gone on the trail a lot this past week. Just had to comment though on the great detail and very accurate color in all of these - really nice job.
If you are looking for a good butterfly field guide, you might want to look into "Butterflies through Binoculars" - not too technical, but usually very helpful.
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