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02-10-2011, 08:52 AM   #1
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TC reviews?

just noticed, pentaxforums doesnt have a TC review section. am i missing it some place? the reason i ask is im intrested in getting a a TC for my sigma 50-150 2.8. i currently have a da L 55-300 but im guessing a simga 50-150 with a 1.5x TC at f/4 and 225mm would be sharp enough and perform better in low light then a da L at 5.6 and 300mm.

the reason im debating my options is last year i went to the 12 hrs of seabring. awesome day but when the sun started to set, the da L was starting to show its weaknesses. i know f/4 to f/5.6 is one stop but that one stop can allow me an extra stop of shutter speed or one stop less of iso.

thanks in advance.

jorge

02-10-2011, 08:56 AM   #2
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I think reviewing TC is difficult because it's all about matching. A TC works great on lens one might be average on another. If you are interested in the Sigma, perhaps checkout the Sigma website and see which is the recommended one.
02-10-2011, 09:02 AM   #3
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Did u look here? I have the Pentax 1.7x af tc and it works with the sigma 50-150mm.

Miscellaneous Lenses for Pentax: Teleconverters (All Brands) - Pentax Third-Party Lens Review Database

Last edited by ivoire; 02-10-2011 at 09:08 AM.
02-10-2011, 10:31 AM   #4
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QuoteOriginally posted by ivoire Quote
Did u look here? I have the Pentax 1.7x af tc and it works with the sigma 50-150mm.

Miscellaneous Lenses for Pentax: Teleconverters (All Brands) - Pentax Third-Party Lens Review Database
How many stops do u lose when using a 1.7x. A stop and a half??

02-10-2011, 11:13 AM   #5
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QuoteOriginally posted by boosted03gti Quote
How many stops do u lose when using a 1.7x. A stop and a half??
That is correct.

And although it's not relevant for use with something like a 50-150mm lens, the maximum (effective) aperture you can use with the 1.7x AF-A is f/2.8. For example, with my DA*55/1.4 or A50/1.2, the lowest aperture I can dial in (accounting for the 1.5 stop loss) is f/2.8 even thought a 1.5 stop loss in aperture size would actually be f/2.4 for the 55/1.4 and f/2 for the 50/1.2.
02-10-2011, 11:56 AM   #6
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Another reason for no TC reviews: it's impossible.

Sure, the Big Names may sell branded TCs, and they may even have had some part in their production. But the vast majority I've seen come from who-knows-where? Where exactly did those Vivitar, Spiratone, Sears, Focal, Promaster, Mepro, Kiron, Kalcor, KFT, Porst, Beck, CPC, Kenko, Panagor, Hama, Albinar, Cambron, Helios, et al TC's originate? (Those are some of the brands of TC's that have passed through my hands lately.)

Or look at Vivitar: I've seen various Viv TC's of obviously different construction but with just the same model ID numbers; and those of obviously the same construction, but with different ID's. And of course they bear no serial numbers, nothing indicating time/place of production, nothing like that. And Viv TC's that are obviously the same as Sears, Spiratone, etc TC's. Tell me, how can any rational rating/review system work with such a maze of models?

OK, so forget the vast majority of TC's, all those disposable off-brands. Just stick to the Big Guys, the ones you pay Real Money for. As mentioned, TC's do or don't match well with specific lenses, so the only rational review system would be of lens+TC combos. Thus, a DA-compatible TC would need to be evaluated with many (or all!!) DA lenses. And with several copies of each. Y'all have fun doing that, y'hear? I've gotta go change the catbox.
02-10-2011, 07:40 PM   #7
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it's kinda annoying that Hoya only made the SP TC for other mounts while Pentax users had to make with the regular TC's. I'm not sure what Pentax/Hoya is trying to achieve by crippling their own market due to unavailability. is Pentax/Hoya trying to promote buying other camera brands just to use their SP TC's?
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