Author Topic: Sal-tc20 compatibility?  (Read 3146 times)

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Offline a700 guy

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Sal-tc20 compatibility?
« on: April 08, 2009, 03:48:40 PM »
I'm hoping someone can help me shed some light (even if it is two stops down:P) on this as I have not been able to find a solid answer.

I'm looking to get the 2x Sony teleconverter for use with my sal-75300 lens. (I'd love to get the G glass but so far I've not been able to embezzle that much money from my family.)

I do know that the minimum 5.6 aperture on my lens will mean I lose AF and I'm ok with that, but I've heard from a SonyStyle stor rep that the two would be physically incompatible. He had no hard information on this but said he was pretty sure that was the case. He seemed relatively knowledgeable about the whole Alpha lineup, but here I am second guessing him.

The store that I was at does not stock the sal-tc20, and they would only get one in if I were to purchase it, so I'm unable to test that way.

Does anyone have first hand experience with this pairing?

Thanks for the help.

Offline Fud

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Re: Sal-tc20 compatibility?
« Reply #1 on: April 08, 2009, 04:49:21 PM »
I'm not certain if Sony operate the same as minolta did but their teleconvertors would only physically work with certain G lenses as there is a problem with non G lenses on how close the glass is to the mount
A900+VG, A77+VG, Minolta 17-35G,  Sony CZ24-70 F2.8,Sony 70-200 F2.8 SSM, Sony 70-400 SSM, Sony 135STF,85 F1.4, 200 F4 Macro, 600 F4 HS APO

Offline Rob aka [minolta mad]

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Re: Sal-tc20 compatibility?
« Reply #2 on: April 08, 2009, 05:08:53 PM »
The Sony 1.4 and 2 x TC,s will only work with the Sony 70-400mm F/4-5.6, Sony 300mm F/2.8, Sony 70-200mm F/2.8 and Sony 135mm F/2.8 but no AF on this lens.

According to kurtmunger.com
http://www.newcamerareview.com/sony_teleconvertersid229.html


Rob

Offline a700 guy

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Re: Sal-tc20 compatibility?
« Reply #3 on: April 08, 2009, 06:08:47 PM »
Thank you both. Just the information I was looking for.

I wish Sony would just say that on their site though. I really thought they were just saying it's incompatible because of the loss of AF.

Offline FarmerDave

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Re: Sal-tc20 compatibility?
« Reply #4 on: April 09, 2009, 05:17:13 AM »
According to your definition, the new 70-400G is incompatible then because although you get 140-800 with the 2xTC, you can only focus manually with that combo (same with the 1.4).
I am afraid it is the physics. The last element of the lens has to leave enough room for the glass elements in the extender. Too bad it doesn't work with the 100mm Macro. Imagine how close you can get!

Offline Bill

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Re: Sal-tc20 compatibility?
« Reply #5 on: April 10, 2009, 03:04:47 PM »
There are 3 issues with T/Cs. 

First are the # of pins.  If the t/c has only 5 contact pins instead of the 8 that are found on the new Sony models, the SSM will not work, thus the lens will not focus.

Second, the Minolta AF system is programmed to autofocus only to f/6.3, with the exception of the 500/8 mirror, which overrides this programming.  The reason for this is that because of the light falloff to the AF sensors as the aperture is stopped down, there is much more hunting for focus lock, which is hard on the entire system from batteries to motors and gears, etc.  Therefore, a 2X t/c will only autofocus with lenses that have an aperture of f/2.8 and faster.  Slower and you must manually focus.

Thirdly, the Minolta and Sony T/Cs will not physically mate to lenses other than those specified.  While 3rd party "universal" T/Cs will mate to any lens, the KM/Sony design has a front element that mates tightly to the rear element of the lenses specified.  While most lenses and third party T/Cs have recessed elements in these areas, the KM/Sony lenses have elements that are much closer to the mount's mating surface plane.  In many cases, trying to mate these incompatable lenses and T/Cs will result in a glass on glass condition.  Forcing the two together can actually physically damage these glass elements.

At least this is my understanding.

Bill
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Offline sonyboy

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Re: Sal-tc20 compatibility?
« Reply #6 on: April 10, 2009, 04:09:34 PM »
The Sony 1.4 and 2 x TC,s will only work with the Sony 70-400mm F/4-5.6, Sony 300mm F/2.8, Sony 70-200mm F/2.8 and Sony 135mm F/2.8 but no AF on this lens.

According to kurtmunger.com
http://www.newcamerareview.com/sony_teleconvertersid229.html


Rob
Just to point out if needed that the Sony converters will work also on the old Minolta G lens that were compatable with the minolta TC.
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