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04-01-2010, 06:38 AM   #1
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Which Teleconverter to use/buy?

Hi Everyone,

I'm thinking about getting a teleconverter but I want to make sure that it will maintain autofocus capability. I'm thinking about using it on the DA* 50-135 as an alternative to lugging around a big huge telephoto zoom. I also want to use it on the Sigma 100-300F4. The 1.4x Sigma APO DG is an obvious candidate at least for the sigma lens. Or is it better that I hold off so that I can use it with my other Sigma HSM lenses (e.g. the upcoming 85mm 1.4 HSM)?

Thoughts?

04-01-2010, 06:50 AM   #2
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QuoteOriginally posted by vandamro Quote
Hi Everyone,

I'm thinking about getting a teleconverter but I want to make sure that it will maintain autofocus capability. I'm thinking about using it on the DA* 50-135 as an alternative to lugging around a big huge telephoto zoom. I also want to use it on the Sigma 100-300F4. The 1.4x Sigma APO DG is an obvious candidate at least for the sigma lens. Or is it better that I hold off so that I can use it with my other Sigma HSM lenses (e.g. the upcoming 85mm 1.4 HSM)?

Thoughts?
beware. the present sigma 1.4x and 2x teleconverters do not support HSM,

Additionally, unless sigma changes their design substantually, I doubt that their new TC (supporting HSM) when it comes available, will support the 85mm lens.

Sigma TCs up to this point are very specially designed to be used with their fast and long lenses, and require the lens have a recess between the back mount and the rear element of about 12mm deep, 35mm in diameter, because the front element of the TC protruces in to the rear of the lens.

The Sigma TCs are great, and offer excellent quality with minimal loss of IQ but are not a general purpose TC.

I am not aware of any current production TC that actually supports HSM, there are some tamron and kenko TCs from the 1990's that can work with HSM because they support the origonal pentax KAF2 mount developed for the power zoom lenses, which use the same power contacts.

I believe functionality is a case by case issue, I don't have any of these TCs so I can't advise further regarding what TCs work with what SDM/HSM lenses.
04-01-2010, 04:34 PM   #3
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This has nothing to do with Film or film SLRs. I'm moving it to the lens section.
04-01-2010, 09:07 PM   #4
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QuoteOriginally posted by vandamro Quote
Hi Everyone,

I'm thinking about getting a teleconverter but I want to make sure that it will maintain autofocus capability. I'm thinking about using it on the DA* 50-135 as an alternative to lugging around a big huge telephoto zoom. I also want to use it on the Sigma 100-300F4. The 1.4x Sigma APO DG is an obvious candidate at least for the sigma lens. Or is it better that I hold off so that I can use it with my other Sigma HSM lenses (e.g. the upcoming 85mm 1.4 HSM)?

Thoughts?
http://www.flickr.com/photos/albert_berry/sets/72157623658994714/
It's not full AF, but fine tunes your focus quite nicely.

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