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04-21-2008, 12:57 PM   #1
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Another Tele-converter Question

Would a Sigma 2x tele-converter work with an M 135mm lens?

04-21-2008, 01:21 PM   #2
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Check the sigma site, I don't think so.

Sigma - Lenses - Teleconverters

the issue is the front element of the TC is flush with the mount, and therefore requires a recessed rear element on a lens to fit. The sigma TC is very specific for particular lenses.

ALso most pentax lenses have a mask that keeps stray light out of the mirror box if it is projected beyond the frame size . This interferes with the elements. I have not looked to see if it can be removed.

I know my K135 DOES NOT fit.

In fact, in looking at all 14 of my lenses. it will only fit on the following:

Vivitar Series 1 70-200 F3.5,
Vivitar 400mm F5.6
Pentax 28-205mm F4.5-5.8 FA
Pentax 18-80 F3.5-4.5 FA
maybe SMC-M 100mm F4 Macro

and of course my Sigma 70-200 F2.8 EX (which i bought it for)

It will not fit on any regular fixed focal length Pentax Lenses, for the above mentioned reason, nor my tamron 24mm f2,5, my Tamron 28-75mm F2.8 of sigma 10-20mm although I don't know why anyone would try this particular lens with a TC

Last edited by Lowell Goudge; 04-21-2008 at 01:30 PM.
04-21-2008, 02:12 PM   #3
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QuoteOriginally posted by Lowell Goudge Quote
Check the sigma site, I don't think so.

Sigma - Lenses - Teleconverters

I know my K135 DOES NOT fit.
The Sigma probably won't fit the M either. I just phoned a local shop and they have a near mint 2x Takumar for $79. That would give me 270mm at 5.6 on my M 135 f/3.5 right?
04-21-2008, 02:33 PM   #4
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QuoteOriginally posted by metalfab Quote
The Sigma probably won't fit the M either. I just phoned a local shop and they have a near mint 2x Takumar for $79. That would give me 270mm at 5.6 on my M 135 f/3.5 right?
your F3.5 would become an F7. not F5.6

I would think this i s not the way to get focal length.

If you really want to get out to 300mm there are a lot of low cost zooms that will do this.

I would recommend a different approach.

Look for a 300mm F4. I don;t think you'll be satisfied with a lot of the slow 300mm zooms

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