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10-07-2015, 12:09 PM   #1
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Pentax 75mm + Sigma FT-1201 ?

Has anyone tried to use the Sigma FT-1201 converter (which is only a 1.2 converter, but without loss of f value, so 2.8 stays 2.8) on the Pentax 645 75mm? It makes it into a 90mm, which is a nice combination with the standard lens, and on the Sigma DP3M it performs extremely well, although it was designed for the DP3Q.

I'm not sure whether there would be vignetting on the P 75mm, and I realize there is an excellent 90mm on 645, but it's sadly just ever so slightly out of my reach.

10-07-2015, 01:13 PM   #2
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Without loss? Impossible because 2.8*1.2=3.4
So a F/2.8 lens becomes a F/3.4 lens if you use a 1.2x converter.

Dura lex, sed lex
10-07-2015, 02:23 PM   #3
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It is a lens that screws into the front of a lens and not a rear teleconverter.

from Sigma's website (

Conversion Lens FT-1201 for SIGMA dp3 Quattro

We are pleased to announce the development of Conversion Lens FT-1201 that is exclusively designed for the SIGMA dp3 Quattro.

When it is attached to the front of the lens, it magnifies the focal length of the lens by 1.2 times (60mm / equivalent to 90mm on a 35mm format), and does not change the f/2.8 aperture value. It consists of 4 ultra-high quality lens elements in 3 groups, and maintains excellent rendering performance while offering a different focal length and therefore more shooting possibilities.
10-07-2015, 04:06 PM   #4
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From experience I can confirm that it does NOT change the aperture value on the DP3 Merrill. What is more, it is so good that i see no loss of sharpness (on the very sharp DP3M lens, APS-C 50mm, FF 75mm; the converter makes it FF 90mm). That's what makes it interesting on the 645, but of course it was not designed for the P 75mm, and I no longer own one, although I'd love to try.


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