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Old Jul 1, 2009, 10:31 PM   #41
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And if the TC isn't chipped, you'll be able to autofocus throughout the zoom range of the lens. Otherwise, you can autofocus at the shorter focal lengths but not the longer focal lengths.
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Old Jul 2, 2009, 6:26 AM   #42
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If staying cheap then the Tamron does OK, I used to have one back in 2005 when I was a Konica Minolta 5D shooter. Jim does suggest that the Vivitar 100-400mm f/4.5-6.7 AF is a strong performer if you need that extra 100mm.
If you need 400mm on a tight budget, I'd probably go that route over a cheap mirror lens, etc. You can usually find these Vivitar lenses for $200 or less.

A few of our members bought one and seem very pleased with it. Here's an old thread that includes a few posts discussing the Vivitar 100-400mm. You'll also see some of photos from it:

http://forums.steves-digicams.com/so...tml#post712189

You can see more photos Gary took at the same game here:

http://www.kleinoakbaseball.com/07ga...30-07/Flash01/
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Old Jul 2, 2009, 6:36 AM   #43
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well thanks for the help guys, i went and got me a Tamron today, it's the DI LD version, when I get some spare cash I will look for a good quality 1.4x or 1.7x converter, is there a particular make I should look for ? I have seen a few makes, the Kenko one and Sony do one that's mega bucks then there is Tamron, Sigma etc, would i be right in thinking the Tamron would work best with a Tamron zoom lens ? I would have thought Tamron would use the R&D dept to optmise their converters for their own lenses ?
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Old Jul 2, 2009, 9:05 AM   #44
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The Kenko Pro 300 and Tamron SP TCs are probably the same (cosmetic differences only) from most reports I've seen.

Those are probably your best bet (the older and cheaper "unchipped" Kenko or Tamron versions without any electronics) since they usually don't report corrected aperture information to the camera. If you try to use a TC that does report corrected aperture, the camera is not going to try to Autofocus (since it's going to see an Aperture value of f/8 using a 1.4X TC on the long end of a dim zoom like that Tamron 70-300mm, which is too dim for the camera to attempt Autofocus). A 2x TC is even worse (as you'll lose 2 stops of light, which means that only about 1/4 the light will get through compared to using the lens without the TC).

But, if you use a TC that doesn't report the corrected aperture, the camera still thinks it's got f/5.6 available (even though you're really at f/8 since you'll lose a stop of light through a 1.4x TC, the camera won't know that and will still try to Autofocus). But, you'll still have less light getting through to the AF sensors, so Autofocus may struggle in less than optimum lighting.

Again, it's probably a bad idea to use a TC on a lens like that Tamron 70-300mm. In addition to Autofocus issues because of loss of light through a TC with a dimmer lens, you'd probably need to stop down the aperture from wide open to help out with the image degradation you'd get using a TC, and you already have significant loss of light through one (so, stopping down the aperture even more is going to require even higher ISO speeds to keep your shutter speeds fast enough to reduce blur).


You may find this page to be of interest (it goes into some of the differences between various TCs available for Alpha mount cameras):

http://www.dyxum.com/lenses/TC/index.asp
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Old Jul 2, 2009, 3:33 PM   #45
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Congradulations on the Tamron. I think you'll like it.

The Kenko Pro 300 and the Tamron SP teleconverters will probably cost more than your lens. They are very good, but they're matched, meaning they only work with a few lenses, and the Tamron 70-300 Di LD isn't one of them. Don't try. You can damage your lens and a very expensive teleconverter.

The ones that will work are the less expensive, lower quality teleconverters. Kenko makes them all, but other companies put their names on them. All 2X TCs are chipped, which means they will report the corrected focal length and aperture to the camera. That would turn your 70-300mm f/4.5-5.6 into a 140-600mm f/9-11, which will never autofocus. No 1.7X TCs, no 1.5X TCs and almost no 1.4X TCs are chipped, so they won't report the corrected focal length and aperture, but the camera won't embed the correct data in the EXIF file header for the image, and it won't correctly compensate for camera shake.
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Old Jul 2, 2009, 5:14 PM   #46
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Are you sure about that (Kenko TC not working with that Tamron)? I see quite a few photos around from Tamron 70-300mm lenses using both 1.4x and 1.5x Kenko TCs. Here's an album with some examples:

http://www.smugmug.com/gallery/62312...10338013_6wn4M

They appear to have better clearance compared to some TCs.

Ditto for the Tamron TCs (which appear to be the same as the Kenkos except for cosmetic differences from what I've read). Tamron even has some web pages showing that combo. Here's one example:

http://www.tamron.com/lenses/tele-guide.asp

Now, I guess it's possible that the newer 70-300mm lenses may be different enough to cause a clearance issue with some camera mounts (it just seems very unlikely it would change enough to cause a problem). Have you seen anyone report any clearance issues trying to use a Kenko TC on a Tamron 70-300mm?
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Old Jul 2, 2009, 7:53 PM   #47
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Are you sure about that (Kenko TC not working with that Tamron)? I see quite a few photos around from Tamron 70-300mm lenses using both 1.4x and 1.5x Kenko TCs.
Those are Kenko's and Tamron's generic TCs, not the Kenko Pro 300 and Tamron SP TCs you said in your post were Tazkb's best bet. The generic TCs will fit anything, including the 70-300 Di LD. The Kenko Pro 300 and Tamron SP TCs are matched, and only work with a few lenses, mostly fast telephoto primes.
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Old Jul 3, 2009, 7:48 AM   #48
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I must admit I find it strange that Tamron's own Tc wouldn't work with Tamrons own 70-300 di ld lens ? surely Tamron would desing their own Tc to work with their own lenses ? if not then it's a bit stupid really don't you think ?
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Old Jul 3, 2009, 8:30 AM   #49
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I would be very surprised if it didn't work with that Tamron, since they show examples of magnification using a TC with a Tamron AF 70-300mm LD lens, with discussion about the Pro series at the bottom of the page about them on their web site:

http://www.tamron.com/lenses/tele-guide.asp

I don't see any noticeable difference in rear element clearance looking at photos of the newer versions of the Tamron 70-300. You'd have to try one to make sure. But, I doubt you'd have a problem with most lenses like that, unless they have a protruding rear element. From the Dyxum page I see about TCs, it looks like the author tested one of the 1.4x Pro models with quite a few lenses that were not on Kenko's "supported lenses" list (including several dimmer Tamrons like the 28-200mm and 28-300mm). My guess is that he didn't have any others to test one with. ;-)

http://www.dyxum.com/lenses/TC/index.asp

Just because Kenko (who also manufacturers Tokina branded lenses) didn't include non-Tokina lenses in their list of "supported" models (which is probably an older list since I see a 35-300 zoom on it), doesn't mean it isn't going to work on them.

Personally, I'd probably stick to the 1.4x versions of the Tamron SP or Kenko Pro 300 for use with that type of lens. I have no way to verify it, but I've seen others say they are the same TC. They should have a bit better optical quality than the non-Pro versions, especially if you use sharper lenses, which is why I'd go that route over a generic TC. On the downside, because they have better optics, you've got less optical clearance than you would with a cheaper generic TC. So, you may have a problem with some lenses that have protruding rear elements.

If you decide to try one, please let us know if it works or not.
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Old Jul 3, 2009, 9:02 AM   #50
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I must admit I find it strange that Tamron's own Tc wouldn't work with Tamrons own 70-300 di ld lens ? surely Tamron would desing their own Tc to work with their own lenses ? if not then it's a bit stupid really don't you think ?
Tamron makes (or rather, sells) two different lines of teleconverters. They make the high end Tamron SP ("Superior Performance") Pro-Series Teleconverters, and the Standard Teleconverters.

From the Tamron website:

"The SP AF PRO-series teleconverters, ... , are designed to be used with lenses that are F/2.8 ... ." (Emphasis mine.)

The 70-300 Di LD does not fall into that category, therefore, the SP Teleconverters are not for use on that lens. The Standard Series Teleconverters can be used on any lens including the 70-300 Di LD.
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