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Leica M240 purple / magenta cast


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Hi!

My Leica M240 just came back from Leica-service and have started to show a purple/magenta cast on the right/top side of the frame, depending on which way it is tilted. 

 

Do you guys have any idea what this phenomenon might be? I've used with 7artisans 35/2 and 50/1.1

 

Really appriciate all the help and thoughts I can get!

 

Thanks in advance!

 

/Fredrik 

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I get the same color cast with my M-P240, but only with my CV 21/4.0.  The CV 35/1.4 and my old Elmarit 90/2.8 don’t have any color cast at all.  

 

From the reading I’ve done on really wide lenses, the color cast is expected and correctable.  I haven’t read about anyone having an issue with the 7artisans lens (regarding color)...just some critiques on bokeh, etc.

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Thanks for all the answers guys! I really do think its the sensor that's misaligned or something, cause it said in the description of the service that they had adjusted the sensor. But tomorrow I'm gonna double check with a Leica lens, just to be sure its not the lenses.

 

Cheers! 

 

/Fredrik 

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I have no experience with the 7art 50/1.1 but i have the 35/2 which protrudes rather deeply into the body. It does not cause color shift on my M240 though. You may wish to try a Leica lens (preferably above 35mm) to be sure but i suspect the problem comes from the sensor as well.

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These pictures are taken today with a Leica summarit 35/2.4 lens - they look pretty good, don't they?

 

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On 6/8/2019 at 9:06 PM, Fredrik_Jalhed said:

have started to show a purple/magenta cast on the right/top side of the frame

It's on the other side too although a little less visible.

It's an effect I'd not be surprised to find on an uncoded wide-angle lens (so no correction applied) but I wouldn't expect to see it from a 50 mm lens.  (I assume your 35 Summarit is 6-bit coded, which might be the reason that it's free of the effect.)

I wonder whether the rear elements of your 7 Artisans lenses protrude too close to the sensor so that rays at the edge of the sensor are oblique and causing this vignetting and colour shift?  You could try retesting the 7Artisans lenses with the M240 coding for a wide angle lens selected to see if it makes a difference.  If it does, you know how to get round it without the pain of sending your camera back to Leica.

Pete.

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Actually, the 7Artisans 50mm f/1.1 has a very deep rear element for a 50 - not surprising that it produces oblique rays we're more used to seeing from a wider, shorter-focus lenses.

Fredrik - this is a well-known phenomenon with classic Leica-type rangefinder lenses whose optics sit close to a digital sensor, and/or produce a wide field of view. Including those made by 7Artisans, Voigtlander, Zeiss, old Canon and Nikon RF lenses, etc. Usually from lenses 35mm or wider - but as I say, your 50mm f/1.1 is built rather like a wide-angle, with that deep back element close to the image plane.

It has to do with the different physical structure of a silicon chip vs. gelatin film. And is basic physics - it is the interaction of the lens and the sensor, not a flaw in one or the other. (I won't bore you with the deeper technical details).

It is the main reason Leica-made M lenses have been 6-bit coded ever since the first M8 digital (2006) - the bar-code on the lens back tells the camera CPU exactly which lens is being used, and the camera's processor can remove the specific pattern of purple stains for that exact lens, automatically as you shoot.

Look at the back of your 35 Summarit f/2.4 mount to see the 6 black-and-white coding dots - that's what told your M(240) processor to remove a similar purple stain using the Summarit.

 ••••.

Since your 7A lenses have no coding dots, you will need to tell the camera which corrections to use by picking a lens type from the Lens Menu in the camera. In other words, the problem is not that they are Chinese, but that they they don't use Leica's proprietary (i.e. patented) coding system. Even many Leica lenses will produce such purple fringes if not coded, and some are not even supported by the software (too extreme a purple pattern - 21 Super-Angulons, 28mm v.1)

It is a question of the exact optical formula of the lens, not strictly focal length and aperture, so you will have to shoot a series of tests with the 7A lenses, identified as a variety of different Leica lenses, to see which setting best removes the purple stains. In other words,  don't assume that setting "50mm f/1.0 Noctilux" will work correctly for your 7A 50mm f/1.1 - "35 Summilux ASPH" or even "21mm Elmarit" may actually do the best job of reducing its particular purple/magenta pattern.

 

Edited by adan
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Just shot this masterwork with a 6-bit coded 7art 35/2 on my M240. No color shift expectedly. Disabling lens profile doesn't change anything through Iridient Developer.

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I've tried everything now with my 7artisans lenses, and I sincerely believe that these copies are just not working that good with my Leica. Yes, with a lot of tweaking, fixing in post process, it maybe could work, for some pictures, but for some pictures it would never work. That itself is reason enough. But the even more, and far greater reason is seeing the M240-files taken with a real Leica-lens just made it so very clear to me that this camera should only be used with Leica glass. 

 

Thanks all for the help and comments! Really appreciate it.

 

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Just now, Fredrik_Jalhed said:

[...] this camera should only be used with Leica glass.

I would not draw such a conclusion. My M240, M8.2 and digital CL work fine with my 6-bit coded 7art 35/2 # 630514 so it is a lens i can only recommend besides its flare issue when strong light sources are just outside the frame. It is a cheap lens though so sample variation is to be expected.

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3 hours ago, lct said:

I would not draw such a conclusion. My M240, M8.2 and digital CL work fine with my 6-bit coded 7art 35/2 # 630514 so it is a lens i can only recommend besides its flare issue when strong light sources are just outside the frame. It is a cheap lens though so sample variation is to be expected.

Ofcourse you wouldn't, or shouldn't. But for me, with the versions I have here, at hand, that's the only conclusion possible. 

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Superb photos can be taken with non Leica lenses on the M240 fortunately. Among my own lenses, i can quote CV 21/3.5, CV 35/2, ZM 35/2.8, ZM 50/1.5, Rokkor 40/2 v2 and Rokkor 90/4 besides the 7art 35/2 and other lenses used by our colleagues on the photo forum. As for my Leica M lenses, most work well on the M240 as expected but some of them need to be corrected in PP like the otherwise superb Super-Angulon 21/3.4 but also the later Elmarit 21/2.8 asph which shows some "italian flag" issues on my body, let alone on yours i suspect given its current problems with the 7art 35/2 already. 

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4 minutes ago, lct said:

Superb photos can be taken with non Leica lenses on the M240 fortunately. Among my own lenses, i can quote CV 21/3.5, CV 35/2, ZM 35/2.8, ZM 50/1.5, Rokkor 40/2 v2 and Rokkor 90/4 besides the 7art 35/2 and other lenses used by our colleagues on the photo forum. As for my Leica M lenses, most work well on the M240 as expected but some of them need to be corrected in PP like the otherwise superb Super-Angulon 21/3.4 but also the later Elmarit 21/2.8 asph which shows some "italian flag" issues on my body, let alone on yours i suspect given its current problems with the 7art 35/2 already. 

You can't compare them brands with the 7artisans, thats just not right. 

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