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06-16-2008, 11:53 AM   #1
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montezuma's Avatar

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TC for 50-135 and when 120-400 comes out

I just got my 50-135mm smc, but now I want more reach. Does anyone know when the sigma 120-400mm lens coems out? Also for now what is a good 1.4x or even 2x teleconverter for the 50-135mm?

06-17-2008, 08:15 AM   #2
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Location: Ontario, Canada
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I have the 50-135 and a few TCs...

My Sigma's wont even fit on it (due to the rear element on the lens - common with trying to use Sigma TCs with non-Sigma lenses - and about half the Sigma lenses too...)

My Tamron 2X MC7 works as a TC but won't auto-focus at all. Slight, but noticeable, IQ loss...

My Pentax 1.7x does auto-focus, but not as quickly as it does with other "fast" lenses. Some IQ loss, but less than with Tamron TC.

Both the Tamron and Pentax TCs produce acceptable pictures, though, of course, none are as sharp as the lens alone. In my (limited) experience with this lens, it's so sharp - for a zoom - that a crop is usually better than using either TC, and it seems that the TC reduces it from an incredible lens to merely a good consumer-quality lens... Of course, YMMV.

(If you take a look at some of the other TC threads, some folks have had good experiences with the better 1.4x's, even getting AF to work sometimes...)
06-17-2008, 09:27 AM   #3
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Has anybody tried the Kenko TCs with the 50-135?

06-17-2008, 05:12 PM   #4
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The Kenko 1.5 works only on manual focus but the images are very sharp. I don't know what's taking Pentax so long to come out with a teleconvertor that works with their DA* lenses.



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