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04-26-2008, 07:37 AM   #286
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QuoteOriginally posted by Peter Zack Quote
So Javier. The 100-300 you got has both the HSM focus system and the screw drive in the same lens? So this lens would work with the Tamron 1.4 TC?
Yeah, I thought Javier was trying it out with the Tammy 1.4x. I don't see any reason why the HSM wouldn't work with this combo.

04-26-2008, 09:03 AM   #287
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QuoteOriginally posted by Peter Zack Quote
So Javier. The 100-300 you got has both the HSM focus system and the screw drive in the same lens? So this lens would work with the Tamron 1.4 TC?
Yes. I am going to try this today.
04-26-2008, 09:55 AM   #288
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Wait a sec, Sigma put hsm in the new batch of 100-300 f4's?
04-26-2008, 11:26 AM   #289
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I would love to see side by side pics of the DA*300 and the SIG 100-300 of the same image with same settings. Tripod mounted and fired by cable release or remote control w/SR off.

04-27-2008, 09:32 AM   #290
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QuoteOriginally posted by Torphoto Quote
Wait a sec, Sigma put hsm in the new batch of 100-300 f4's?
No, that's someone's wishful thinking. There is no HSM for Pentax or Sony. Sigma - Lenses
04-27-2008, 02:24 PM   #291
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QuoteOriginally posted by clm Quote
No, that's someone's wishful thinking. There is no HSM for Pentax or Sony. Sigma - Lenses
Somebody should sue Amazon for false advertising: Amazon.com: Sigma 100-300mm f/4 EX DG IF HSM APO Fast Aperture Telephoto Zoom Lens for Pentax and Samsung SLR Cameras: Camera & Photo.
04-27-2008, 02:28 PM   #292
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The false info is in the name of the product, in the technical details Amazon says "Hypersonic motor: No" - confusing!

But Javier seems to argue, that it has HSM, now how is it!
04-27-2008, 02:52 PM   #293
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QuoteOriginally posted by gawan Quote
The false info is in the name of the product, in the technical details Amazon says "Hypersonic motor: No" - confusing!

But Javier seems to argue, that it has HSM, now how is it!
Javier did say the HSM didn't work. And that would be because there is no HSM. Javier, be clearer next time!

04-27-2008, 03:35 PM   #294
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QuoteOriginally posted by jgredline Quote
Thanks a bunch for the kind words. Well, Today I took out both my new Sigma 100-300 F/4 and Pentax DA*300 F/4....So far, there is no difference what so ever..None, nada that I can see. I will post some pics tomorrow. By the way, the Sigma 100-300F/4 with out the Sigma TC's HSM motor is quiet and extremely fast and precise. Amazon had three of them when I bought it. I was surprised it was HSM as I thought Sigma was not going put it on pentax mount. With the Sigma TC the HSM does NOT work and it is still pretty fast to auto focus, but noisy...

When I was looking for it, I called Adorama and they had this one.
Sigma 100-300mm f/4 EX DG IF AutoFocus Telephoto Zoom Lens for Pentax AF Cameras I am pretty sure this is an old model, but really good.

This is the one I bought.
Sigma 100-300mm f/4 EX DG IF HSM APO Fast Aperture Telephoto Zoom Lens for Pentax and Samsung SLR Cameras
Amazon.com: Sigma 100-300mm f/4 EX DG IF HSM APO Fast Aperture Telephoto Zoom Lens for Pentax and Samsung SLR Cameras: Camera & Photo
Along with the dedicated TC that only works with certain APO lenses.
I tried to use this TC on some of my other lenses, but would not even fit.
He says Amazon has the HSM one for Pentax
05-02-2008, 07:07 PM   #295
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$136.50 shipped for new Tamron 1.4x teleconverter at eBay

Tamron 1.4x teleconverter
05-02-2008, 08:41 PM   #296
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QuoteOriginally posted by thear Quote
$136.50 shipped for new Tamron 1.4x teleconverter at eBay

Tamron 1.4x teleconverter
I saw this auction a couple of days ago. Unfortunately the seller won't ship OS.
05-03-2008, 04:09 AM   #297
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Cool, thanks for the post, now I can get another one for when I get the DA*300.
05-03-2008, 05:10 AM   #298
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Excellent tc info thread,
Just to add my 2cents; I only have one sdm lens, the da 300 and it works great with the pentax 1.7 afa(no sdm of course) but the kenko pz-af 1.5x teleplus shq will use the sdm but it focusses back and forth not locking in very good. It has 7 contacts on the lens side and six on the camera side. That is with the k10d or the super, I wonder how long for a new pentax sdm tc?
05-03-2008, 05:43 AM   #299
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I bought a Kenko Teleplus DG 1.5x recently. I was going for a Tamron at first but there are difficulties finding them in Europe. I wasn't too bothered buying Kenko as I was happy with the IQ that my Teleplus MC7 DG 2x produced.

With all these TCs though there seem to be idiosyncracies whatever the brand. When I looked at the Tamron specs at places such as Cordcamera it says "full AF operation is only possible with lenses with open aperture of f/2.8". Yet people seem to get autofocus with lenses like the Sigma 70-300 F4-5.6.

My Kenko 1.5x will give me SDM focusing with the K10D plus DA*300 (there is a little hunting at times but other times it locks on pretty fast, perhaps to do with variations in light/contrast). I would expect it to autofocus as the specs say it should autofocus with lenses with open aperture of F4.5 or brighter. With the 2x, I get autofocus with my Sigma 70-300 at 70mm but I have to manual focus at 300mm. Again, this is to be expected as the specs say it will autofocus with lenses of open aperture of F4.0 or brighter. But with the DA*300 I have to use it on manual focus even though with a constant F4 I would have thought I should be able to get autofocus. Contacts on the TCs, lens and camera side, seem to be identical.

Any thoughts on why the Tamron appears to give AF with lenses of open aperture smaller than F2.8 and why I can't get AF with my Kenko 2x, even though the DA 300 is a constant F4?

Paul
05-03-2008, 06:22 AM   #300
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AF capability depends on how large the aperture looks like from the AF sensor's position of view.

Common wisdom says that it needs to be f/5.6 or wider (which is a minimum angle) . Of course, with TC mounted if it has to AF with TC.

So, with 1.4x, it is f/4 and with 2x TC it is f/2.8 w/o the TC.

Because of slight variation in optical formula, the exact visible virtual size of the aperture may vary by +/- 1/2 EV. But that's it.

If you go for smaller apertures, the contrast in the AF sensor blacks out (just like with the focus indicator in conventional focus screens) and it stops working. It is quite a binary transition.
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