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09-27-2012, 09:58 AM   #1
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2x converters

I need some help with converters. I have found two different 2x pentax converters and can't tell the difference other than $$. One is listed as a
2x-s converter A the other is a 2x rear converter K T6. Can someone explain the differences? I want to use one on a 70-300 Tamaron lens on my K-5. I realize niether has AF and I can live with that. Would like thoughts, suggestions, and info.

09-27-2012, 10:04 AM   #2
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See here:
Pentax K-mount Teleconverters and Adapters - Lens Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database

Essentially, the A one supports auto-aperture.

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09-27-2012, 10:10 AM   #3
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One of the things to look out for with the rear converters is they may project into the rear of the lens, and are only meant for long fast lenses.

You will need to check this point
09-27-2012, 11:08 AM   #4
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The A version supports shutter-priority auto-exposure mode. The K has auto-aperture (doesn't require stopping down the lens to allow the light meter to measure the light), but doesn't permit shutter-priority auto-exposure .

09-27-2012, 06:46 PM   #5
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You might also want to search for other threads on tc's and using them with consumer zooms lime the tamron 79-300. Not only do you lose af, but you lose two stops of light, making it harder to manually focus, harder to get a fast enough shutter speed, plus SR won't have the correct focal length info and thus won't be as effective - and the end result will almost certainlly be noticeably worse quality than simply cropping the image without a TC. In other words, money spent and extra trouble just to get a worse image than you could get more easily for free by cropping.
09-28-2012, 09:46 AM   #6
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Thanks Marc,
So instead of a 2x converter, what would say about either the Sigma 600mm mirror lens or the Pentax 400-600 F8-f12 telephoto lens?
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