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03-22-2014, 03:40 AM   #1
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Sigma 1.4x DG EX APO Teleconverter

Hello,

I was thinking about getting a Sigma 1.4x DG EX APO Teleconverter but I was wondering...

Is the TC worth buying ? I read the reviews on this forum and it looks quite good but... in a more practical way :

Is it worth putting it on a 500mm ? I got a 80ED telescope lens, used in a prime focus setup. It gives very good IQ, so is it better to crop or to use the TC (and crop even more? ).

As a consequence, does this TC work with manual focus lens ? Because my 80ED is connected through a T2.

Thank you !


03-22-2014, 05:54 AM   #2
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Before anything else, consider you need an opening at the end of the lens 35mm in diameter, 12 mm deep, because the front element of the TC protrudes into the lens
03-22-2014, 06:34 AM   #3
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There is nothing to worry about that, there is a long macro tube so that MDF is relatively small.

However, as there is no electronic, will the TC work ? I mean, will my DSLR still ask me "what focal length" am I using ?
03-22-2014, 06:40 AM   #4
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There are a lot of ED80 telescopes on the market. Dublets, triplets, quadruplets, with different sort of ED glass. Some are good, others are very good, and other not so. Anyway, you can use it with a TC. And the TC with manual lenses.

But, because photo TC are made to be used with photo lenses, which are corrected for flat field, I think it will work best with a field flattener put between telescope and TC, or without, if you have a quadruplet ED telescope, because those are corrected for flat field. That doesn't mean that will not work without a field flattener. but can be a difference.

Anyway, how good the result will be, I think that only someone with the same setup like yours can tell.

PS. Yes, your DSLR will ask about focal length.

03-22-2014, 09:01 AM   #5
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QuoteOriginally posted by DiY171 Quote
There is nothing to worry about that, there is a long macro tube so that MDF is relatively small.

However, as there is no electronic, will the TC work ? I mean, will my DSLR still ask me "what focal length" am I using ?
The TC will work without electronics, providing that you can offer shorted connections , as later pentax DSLRs will not let the shutter trip if there is no shorting of the Lens contacts.

Just make sure that the mount and/orextension tube are conducting not painted
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