6bit oding adventures with CV 12/15/21/28 lenses

[edlaurpic]

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I tried to manually code four CV lenses yesterday - the 12 and 15 heliars and the 21 and 28 skopars. The Leica adapters I used were all marked 9cm. The camera has been to Solms for the "upgrade" and has the latest firmware. I used 486 UV/IR cut filters on all of the lenses. Lens recognition was enabled in the menu.

 

I succeeded in having the proper focal length show up in the exif data for all of the lenses, but there is strong cyan in the corners of both the 12 and the 15 on which I used the CV step up ring, then stepped down to take a 67 UV/IR cut. Vignetting was the same with or without the step down ring and 67 filter, but the cyan corners were very strong with the 12 and 15 when the filter was in front of the lens.

 

The good news is that the 21 and 28 had only mild cyan in the corners.

 

Questions:

 

Did I code the lenses correctly? For the 12, 15, and 21, I coded them as a 21/2.8 elmarit. For the 28, I coded it as a 28/2.8 (not as an f/2 summicron). These seemed to be the closest lenses to the CVs.

 

Second, is it correct that coded lenses on which UV/IR cut filters are attached will reduce or eliminate the cyan corners? Or is that only with the next iteration of the firmware?

 

Any insights you may have would be appreciated.

[edlaurpic]

I forgot to mention that the 28 frame line came up for all of the lenses in the viewfinder, but the 12, 15 and 21 showed 21 in the exif, while the 28 showed 28 in the exif.

[marknorton]

The existing firmware will reduce the cyan a bit but it's not until 1.10 when we expect to be able to tell the camera there's an IR filter on the front and have it correct the cyan more fully.

 

Other than the 21mm Elmarit, the only wider lens is the nre Tri-Elmar, so it you might think of coding that lens. As far as we know, you will not see any focal length reported for this lens because the lens does not tell the camera what the selected focal length is.

 

The frame line you see in the camera depends only on the bayonet ring, not the coding.

[sean_reid]

Hi Ed,

 

The 28 Skopar will do a bit better coded as 28 Summicron Asph. The 21 works well coded as you have. Both of these should correct cyan drift much better once firmware 1.10 is out.

 

You can reduce vignetting by coding the 12 and 15 as 21s but the cyan drift correction won't even be close. I recommend using those two lenses with no filter and processing with Jamie's profile.

 

Cheers,

 

Sean

[scott kirkpatrick]

I tried to manually code four CV lenses yesterday - the 12 and 15 heliars and the 21 and 28 skopars. The Leica adapters I used were all marked 9cm.

 

The good news is that the 21 and 28 had only mild cyan in the corners.

 

Questions:

 

Did I code the lenses correctly? For the 12, 15, and 21, I coded them as a 21/2.8 elmarit. For the 28, I coded it as a 28/2.8 (not as an f/2 summicron). These seemed to be the closest lenses to the CVs.

 

Second, is it correct that coded lenses on which UV/IR cut filters are attached will reduce or eliminate the cyan corners? Or is that only with the next iteration of the firmware?

 

 

Congratulations.

 

In firmware 1.06, the vignetting correction for the Summicron 28 was a little stronger than for the Elmarit 28, but since the Elmarit needs more, it may get a stronger correction in a future firmware release. I would stay with that identification for now.

 

So far the firmware is only designed to correct the red vignetting (cyan drift) without an IR-cut filter. There is some because of the greenish filter over the M8's CCD chip which stops most but not all IR and reduces red to something more like human sensitivity. Light passing through this filter at an angle gets more red reduction than it needs. Future firmware will add a second correction for an IR-cut filter in front of the lens. Hopefully, this will be a menu option, not a requirement, but we don't know that yet.

 

scott

[edlaurpic]

Thanks very much for your comments, suggestions. I will await the next firmware upgrade.

 

I am not sure where or when in any other forum devoted to cameras or photography I have seen so fast and thorough a response ... and this happens often on this forum, for which those of us with less experience and skill should be grateful.

[J_Brittenson]

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How did you manage to put a filter on the 15? Some sort of slip-on filter holder?

[gtmerideth]

WE are very grateful!

g.

[sean_reid]

How did you manage to put a filter on the 15? Some sort of slip-on filter holder?

 

With a little tape on the barrel, one can mount a filter on the 15 using the holder intended for the 12 - but I wouldn't. <G>

 

BTW, I'm still hoping for some odes in this oding adventure. Ode to the M8...owed to Mastercard after buying the M8...dropped my M8 on a Grecian Urn...something <G>

 

Cheers,

 

Sean

[EricC]

Questions:

 

Did I code the lenses correctly? For the 12, 15, and 21, I coded them as a 21/2.8 elmarit. For the 28, I coded it as a 28/2.8 (not as an f/2 summicron). These seemed to be the closest lenses to the CVs.

 

Any insights you may have would be appreciated.

 

Hello,

 

Thank you for doing these tests.

 

I would have thought that it may have been a better option to code the 12 and 15 using the code for the New 16-18-21 Tri-Elmar as the 16mm wide end is closer to the 12 and very close to the 15.

 

EDIT : Ooops, didn't see Mark's post above.

 

All the Best

Eric