Cyan corners and non coded lenses

[artur5]

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Now than I.R. filters seems to be mandatory with the actual M8, as a potential owner my main problem is that I have Zeiss and CV lenses, thus I won't benefit from the Coding that Leica will use to correct vigneting and cyan corners on WA glass.

It's unlikely that Leica will update the firmware with a menu option to manually select the lens -as suggested wisely on this and others forums.

Vigneting is easy to fix, but cyan corners are nastier.

I wonder if any of you -Photoshop gurus - would care to make a sort of plugin or Pshop action to bypass the problem . Somebody hinted to apply a circular gradient mask and correct the curves for the red channel.

I'm not by any means a Pshop expert, rather a beginner. What do you think ?

Of course it would be vastly better to have the Raw file already corrected, but I can't afford to throw away all my lenses and invest 8000 Euro on Leica glass.

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[tashley]

Maybe you could experiment instead with manually coding your lens with the same dot patter as Leica glass with the same or very close focal length. There's a thread about that somewhere here. Probably rather a hack solution but it might just work - I don't fancy trying to get the right radial pattern in a PS layer, especially when there's no EXIF to tell you what the aperture was, since I think (willing to stand corrected) that that is also a relevant variable.

 

I have a CV 15mm and I think I'll largely use it for B&W but even that could be affected by radial shifts so I'd be curious to know if anyone thinks the suggestion I make here about home coding might work?

 

Tim

[marknorton]

If the cyan is aperture related, we all sunk anyway since the camera doesn't know what the aperture is.

[waterlenz]

If the cyan is aperture related, we all sunk anyway since the camera doesn't know what the aperture is.

 

Aperture will not relevant since there is no way even a coded lens can transmit to the camera what aperture is being used. I would look to a menu option being implemented in C1 (hint- hint to C1). There may be need for a couple of variables, which could be adjusted by slider in the GUI. It may not be as simple as just focal length. We will have to wait and see.

Tom

[marknorton]

Yes of course - but does the level of cyan fringing vary with aperture or is it only related to focal length and (may be) exit pupil size/location?

[waterlenz]

Yes of course - but does the level of cyan fringing vary with aperture or is it only related to focal length and (may be) exit pupil size/location?

 

If it varies by aperture then it is not getting fixed for even coded lenses.

Tom

[artur5]

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Maybe you could experiment instead with manually coding your lens with the same dot patter as Leica glass with the same or very close focal length. There's a thread about that somewhere here. Probably rather a hack solution but it might just work - I don't fancy trying to get the right radial pattern in a PS layer, especially when there's no EXIF to tell you what the aperture was, since I think (willing to stand corrected) that that is also a relevant variable.

 

I have a CV 15mm and I think I'll largely use it for B&W but even that could be affected by radial shifts so I'd be curious to know if anyone thinks the suggestion I make here about home coding might work?

 

Tim

 

I wonder how accurate is ( or will be ) Leica's correction if the camera's CPU doesn't know the aperture.

Even if aperture isn't of great relevance, it's a PITA. to correct every file because you have to know also which lens was used.

Your hack solution would a better way, but it's not so easy as to paint black and white dots in the mount. I haven't seen any coded lens, but I think the dots are engraved and filled with paint afterwards ?

LTM glass should be easier and cheaper to fix, with a coded adapter no need to modify the lens. There's room for a third part company here, if Leica didn't patent the whole thing. As I read somewhere, the classic M to LTM adapters could be made with two different codes engraved -one for each focal supported - i.e. a 28-90 ring for 28mm. and another one for 90mm.

Anyway, the optical design of a 21mm. Elmarit it's not exactly like a 21mm.Zeiss so we'll get only a rough correction. The CV12 and CV15 are still worse because there's no Leica equivalent on this focal.

[gravastar]

I've found that the PT Correct/Radial Luminance function of the free Panorama tools 16 bit plugin for Photoshop looks very promising. It allows you to correct vignetting and cyan corners in one operation. You need both the 16bit pano12.dll and the plugin. What I don't know yet is what you do if the correction needed is non linear, ie. not proportional to radius. I'm waiting for an M8 and filters, so it's early days yet.

 

Panorama Tools Plug-ins (16-bit)

Panorama Tools Tutorial for Printable Panoramas

 

I believe that because of expertise in third party tools development it's essential that Leica give the option of disabling corrections to RAW files.

 

Edited to add: I guess this is where the "mapping" of the sensor output to 8 bit RAW could be a problem. For optimum results any corrections need to be done before the data is mapped to 8 bits. For that reason Leica may never offer the disabled option.

 

Bob.

[nemeng]

I've found that the PT Correct/Radial Luminance function of the free Panorama tools 16 bit plugin for Photoshop looks very promising [...]

 

More than just "very promising" :?)

 

Many professionals have been using PTools for years to correct barrel distortion, chromatic aberration, vignetting etc.!

 

FWIW there are simpler interfaces to using PTools - see:

 

Mac OS X: LensFix & Panorama Tools plug-ins

 

Wintel: PTLens

 

The following wiki entry may also be of use:

 

Panorama Tools Plugins - PanoTools

[ho_co]

I guess this is where the "mapping" of the sensor output to 8 bit RAW could be a problem. For optimum results any corrections need to be done before the data is mapped to 8 bits.

Bob--I understand that you say 'optimum results,' but couldn't one convert back to 16-bit to apply the correction?

 

--HC