CV lens code

[gmbandera]

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Someone has codified cv lens?

And in that way?

I tried but... wrong result!

 

Thanks

 

Best Regards

 

Gian Mario

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[cbretteville]

Whatever has been tested and found to work you'll find at Casten's site: Leica M8 Lens Codes

 

Two CVs listed at this time.

 

- Carl

[gmbandera]

ok

Thanks!

 

Gian Mario

[sean_reid]

I did the coding and testing for the CVs listed on Carsten's page. They do work, but the Ultron 28 is slightly over-corrected in the corners because it vignettes less than either of the current Leica 28s.

 

Cheers,

 

Sean

[waterlenz]

I did the coding and testing for the CVs listed on Carsten's page. They do work, but the Ultron 28 is slightly over-corrected in the corners because it vignettes less than either of the current Leica 28s.

 

Cheers,

 

Sean

 

The best correction may not necessarily be by emulating a Leica lens of the same FL.

T

[carstenw]

True enough, Tom, but I do believe that the right frames have to be selected. In that case, if you can't find a suitable 28mm lens to use for the CV28, you might need to try a 90 That will look funny in the EXIF.

[waterlenz]

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True enough, Tom, but I do believe that the right frames have to be selected. In that case, if you can't find a suitable 28mm lens to use for the CV28, you might need to try a 90 That will look funny in the EXIF.

 

 

What is more important to you, correcting for the cyan in the corners or having the right EXIF data? For example, I have an after-market chipped Nikon AI lens which works fine but the lens ID is all wrong, no big deal, but it meters OK on a D70, which it otherwise would not.

T

[grober]

Someone please discover then broadcast the best coding for the ZM 25mm Biogon. Given the right 6-bit code I may not sell this lens after all.

 

I can't try anything 'cause my M8 is in Germany for the recall.

 

Thanks!

 

-g

[carstenw]

Tom, clearly the right correction is more important, but I might accept a slightly wrong correction if I had "correct" EXIF data. In any case, for the Ultron 28mm, I would guess that the Leica 28mm f/2 or f/2.8 will be closer than a 90mm. I am sure that Sean will tell us one day.

[sean_reid]

The best correction may not necessarily be by emulating a Leica lens of the same FL.

T

 

If only it were that simple. <G> There will be two primary kinds of correction in 1.10. The first is for vignetting, which of course can vary widely even among lenses of the same nominal focal length. The second is a color correction for the cyan drift, which tends to be more consistent among lenses of a given focal length.

 

The correction itself is triggered not only by the code but also by the position of the frame lines selector. As Carsten points out, a 28 could be coded as a 90 but I doubt that would be a very useful thing to do, esp. since a 28 will show cyan drift and a 90 will show none.

 

If one tries to use a 35 LTM adapter, the wrong frame lines will be triggered and the cyan drift correction will likely be incorrect as well. It might be a better match to a given 28 with respect to vignetting but is problematic nonetheless.

 

If you start playing with these lenses and hand coding them you'll soon see what I mean. There may possibly be something gained from coding a 50 as a 75, or vice versa, but in general I think a lens will do best coded as a lens of the same nominal focal length.

 

Cheers,

 

Sean

[LJL]

J.W. (grober),

I am with you on this wish also. My present thinking is that there is something between the framelines marker and the coding that results in cancellation. One can just mark the lens with a black marker, but one cannot get the lens to call up the 24mm frameline set on the M8. That suggests that the 28mm frameline set that the Zeiss 25 calls up does not have a working code with the 24mm coding. Somebody, I thought, had posted a message saying that Zeiss was looking into a "retrofit" of the mount that would bring up the 24mm framelines for the M8. If that becomes true, then the hand coding wth the black marker may work. Until then, I think we are just hoping and waiting. (I really like the Zeiss lens also, and have been using it without filters in good light, but I bought it to use as much indoors and under more challenging lighting conditions. So far that is a gamble when shooting. I did get a step-up ring to handle a UV/IR cut filter that I have for other lenses, but it means no lens hood, and then has a bit of cyan corner issues.)

 

LJ

[sean_reid]

J.W. (grober),

I am with you on this wish also. My present thinking is that there is something between the framelines marker and the coding that results in cancellation. One can just mark the lens with a black marker, but one cannot get the lens to call up the 24mm frameline set on the M8. That suggests that the 28mm frameline set that the Zeiss 25 calls up does not have a working code with the 24mm coding. Somebody, I thought, had posted a message saying that Zeiss was looking into a "retrofit" of the mount that would bring up the 24mm framelines for the M8. If that becomes true, then the hand coding wth the black marker may work. Until then, I think we are just hoping and waiting. (I really like the Zeiss lens also, and have been using it without filters in good light, but I bought it to use as much indoors and under more challenging lighting conditions. So far that is a gamble when shooting. I did get a step-up ring to handle a UV/IR cut filter that I have for other lenses, but it means no lens hood, and then has a bit of cyan corner issues.)

 

LJ

 

I spoke with my contact at Zeiss in September about changing the bayonet on the 25 and they're very interested in doing that but have not yet made any official announcement. To use a hand-coded ZM 25 on the M8 now (if one wants to trigger the corrections), one must hold the frame lever in the 24/35 position which obviously is not practical for most work.

 

The ZM 21 is in the same boat.

 

Cheers,

 

Sean

[LJL]

Thanks, Sean. I thought it was you that had looked into this, but I was not sure if the info came from this forum or our PMs.

 

I am all for Zeiss building a new "M8-mount" for the 25/2.8. Put me on any communication/voting/suggestion/request list, etc., that may help that cause. It is great lens and I really would like to be using it in a less restricted mode. I too have thought about selling it and getting the Leica. I still may, if just to have the convenience and features of use that the Zeiss COULD easily have with a relatively small change.

 

Thanks again for all your efforts and inputs. They are appreciated. Happy Holidays also!

 

LJ

[waterlenz]

If only it were that simple. <G> There will be two primary kinds of correction in 1.10. The first is for vignetting, which of course can vary widely even among lenses of the same nominal focal length. The second is a color correction for the cyan drift, which tends to be more consistent among lenses of a given focal length.

 

The correction itself is triggered not only by the code but also by the position of the frame lines selector. As Carsten points out, a 28 could be coded as a 90 but I doubt that would be a very useful thing to do, esp. since a 28 will show cyan drift and a 90 will show none.

 

If one tries to use a 35 LTM adapter, the wrong frame lines will be triggered and the cyan drift correction will likely be incorrect as well. It might be a better match to a given 28 with respect to vignetting but is problematic nonetheless.

 

If you start playing with these lenses and hand coding them you'll soon see what I mean. There may possibly be something gained from coding a 50 as a 75, or vice versa, but in general I think a lens will do best coded as a lens of the same nominal focal length.

 

Cheers,

 

Sean

 

This redundancy in the FL coding (redundant other than with a Tri-Elmar) is bad news for 3rd party and non-coded Leica lenses of FL for which VF framelines are available. I guess one could put up with the wrong framelines to get better correction (e.g., not use the 28/90 LTM adapter with the Ultron 28, but the one that matches the FL of the Leica lens with the best correction if that lens is not a Leica 28; maybe one of 35's for the Ultron). This may be less of an issue for the short FL lenses, here one would select the best correction match regardless of FL since one would be using a separate finder anyway.

[waterlenz]

J.W. (grober),

One can just mark the lens with a black marker, but one cannot get the lens to call up the 24mm frameline set on the M8.

 

LJ

 

The frameline selection is purely mechanical - M3 legacy technology.

T

[artur5]

I spoke with my contact at Zeiss in September about changing the bayonet on the 25 and they're very interested in doing that but have not yet made any official announcement. To use a hand-coded ZM 25 on the M8 now (if one wants to trigger the corrections), one must hold the frame lever in the 24/35 position which obviously is not practical for most work.

 

The ZM 21 is in the same boat.

 

Cheers,

 

Sean

 

For Zeiss It would be very easy to fit a ZM35/2 bayonet ring on the ZM 24 and a ZM 28/2.8 bayonet ring on the ZM 21/2.8 in order to invoke the 24/35 and the 28/90 frame lines as Leica lenses do.

As far as I know, all the Japan made ZM lenses share the same ring -fixed to the lens body with 3 screws -at least the ZM35 and the ZM21 that I own. Obviously, the key flange for each of the 3 pairs -28/90 -24/35 -50/75 is different.

I even ordered a replacement ring for a ZM28 on the Zeiss web site some weeks ago, but I got no answer ..

[sean_reid]

Easy if one can get those screws loose. I couldn't do it. The ZM 25 and ZM 21 each have 4 screws holding the bayonet on and they must be in with loctite or the equivalent.

 

Cheers,

 

Sean

[hrosell]

Hi Sean,

 

This is a personal msge to you (sorry to bother the thread) but have been trying to reply to your kind and reassuring mail without success as it seems you have reached your storage quota!

Thus, many thanks indeed and Merry Xmas to you – and to everyone else in this forum.

Enjoy!!!

 

Horacio

 

===

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Hallo,

Look here: Interesting Leica gear

[jaapv]

There is an interesting side-effect to this. If one wishes to switch OFF the lens detection for a single shot, for instance to restore the natural vignetting of a lens, it is not necessary to go into the menu. Just press the frameline selector lever.

[waterlenz]

There is an interesting side-effect to this. If one wishes to switch OFF the lens detection for a single shot, for instance to restore the natural vignetting of a lens, it is not necessary to go into the menu. Just press the frameline selector lever.

 

This is one for the 'hidden feature' department.

T