Zeiss Contax G M-mount Lenses

[koji]

First time posting.

Hacker's lens test results from MIYAZAKI-optical, who actually did the modification to
all those Contax G-lenses, says in the left lower corner is roughly>

Round figure is an image from interferometer
...colour distortion (ie. CA) is small ... good
...glass has no "striae"
...glass has good polishing/making

Right of the above figure is diagram of spherical aberration
...full correction & bump is very small
it can be said that this lens is an almost perfect non-aberration lens,
it has very good front and back bokeh, and you cannot find a better
lens.
...multi magenta coating and good against flare and ghost
...neutral colour rendering
...good construction i.e. lens has no de-centering

----------------------------

I have also converted G-Biogon 21/2.8 in Tokyo, the result with M8 is
quite good. However its file does not work with "cornerfix" well, since
right fall off is too steep for this soft to handle? I now put 6-bit coding
to the lens' L-M mount, and use "cornerfix" to correct cyan corners.

I did modify G-Sonnar 90mm to M-42 mount myself, the result is very good too.
one large example > http://www.pbase.com/kkawakami/image/69121574/original

By the way, nice shots of kids.

 

[Hacker]

Thanks Koji, especially for the wonderful translation. Can you post a picture of your modified lens also?

Welcome to DPI!

Stephen

 

[koji]

Hi Hacker,

PBASE does not work with

faclity well, here is my modified G-Biogon>
http://www.pbase.com/kkawakami/contaxgs

Modified G-planar 2/45 is not mine, just used one week freely before sending it to my friend
in USA after carrying them into Canada. Infinity focusing with Planar 2/45 was not problem, but
Biogon 2.8/21 was tough to fix although it focuses correctly now. I think they made a booboo,
linkage cum was not correctly fixed and adjusted. But I fixed it myself, this was lots of fun.

 

[sandymc]

I have also converted G-Biogon 21/2.8 in Tokyo, the result with M8 is
quite good. However its file does not work with "cornerfix" well, since
right fall off is too steep for this soft to handle? I now put 6-bit coding
to the lens' L-M mount, and use "cornerfix" to correct cyan corners.

Koji,

CornerFix should work fine with a 21mm lens; it can handle the CV 12mm, so I'd be surprised if there was a problem.

My suggestions would be first, check that the reference image you're using (the one of a grey card, or white wall or whatever) is reasonably evenly lit. If that doesn't work, select "Multiple Equation" mode in CornerFix when you generate the profile for the 21mm.

If all else fails, send me the reference image, and I'll take a look at it. Contact info is in the PDF file that came with CornerFix, or you can PM me here, or on the LUF. I'm more often on the LUF though...

Sandy

 

[koji]

Sandy,

Thank for your advice, I finally managed to get a reasonable result using
CornerFix with G-Biogon 21, but my M8 is broken now (actually I did) so
I cannot experiment now. I will find out some original DNG files taken by
this lens then experiment more.

 

[lamman]

Hi Koji, I'm a newbie here too. As I found no focusing tab in the converted G21 lens. Did you find any difficulty turning the aperture and focus rings?

 

[Hacker]

Size comparison against the Nikkor-P.C 8.5cm f/2 LTM:

 

[D.Rokkor]

My LTM converted G-Biogon 21/2,8 has arrived, straight from JapanExposures :rock:

More pics here : http://flor27.free.fr/Carl_Zeiss_G-Biogon_21_2.8_LM_conversion/