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24mm Lux w/ SL- purple center spot issue


Hlarocca
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Not all that wrong.

Lens coatings do make use of wavelength interference, but to "destroy" reflected light, rather than split it dichroically and send different wavelengths/colors in different directions.

 

Oddly, though, when I used a Heliopan 39mm UV/IR filter on my M8 and 15mm Voigtlander, I did mount it backwards - and it performed normally. I reversed it so that the filter frame would fit over the curved front element, like [(, and wedged it into the built-in tulip lens shade of the CV by wrapping several layers of thinly-sliced black photo tape around the rim of the filter to "fatten" it. Never came loose.

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farnz and adan,

I really appreciate your insight. 

 

It does seem like the issue is worse in bright/ daylight conditions.  I haven't noticed it indoors.  I'll have to do more experimentation when I get a chance.  I don't want to have to avoid packing the lens on my excursions because of the issue, but my confidence level in it's ability to perform normally is waning and it's frustrating to have such an expensive lens with such an ovious anomaly.  Is this kind of spotting easily removed in photoshop?
BTW- I have the new 35mm Lux-M ASPH w/ Floating Element, if it also has a concave rear element it certainly has never exhibited this issue. 

Any suggestions on what I can do?  Should I send the lens in to Leica for an inspection?  if this is a lens design flaw/ issue, then certainly I shouldn't be the only one to have this problem?

 

Again, thanks much!

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Did you use a lens shade? Or did the sun shine directly onto the front lens element? Try to do a comparison shot, one without lens shade and the other one with lens shade (or with someone shading off the sunlight with his/her hand). I am pretty sure this is a reflection/flare issue originating from a strong point light source (such as the sun) shining into your lens.

 

Andy

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Hi, Hariocca,

 

If my theory is correct then there's not much you can do to make the sensor less reflective without degrading the image quality or damaging the sensor and the same goes for the rear element of your Summilux.

 

You can reduce the purple spot's visibility in post-processing and the way I would approach it is to pull the picture into Photoshop, convert to LAB colour space (so that all your colour information is separate from the luminance/brightness information) and add a Curves adjustment layer.  This will allow you to adjust the purple spot's colours in the A and B channels by increasing green, increasing red slightly, decreasing blue, and increasing yellow slightly.  Then invert the Curve adjustment layers mask and apply the colour changes to only the purple spot so that the rest of the picture is unchanged.

 

I've attached an adjusted jpeg example from your dropbox link to show you the effect.  It's not perfect by any means and using the DNG file would have let me get closer and I spent no more than 15 minutes on it to get it to this point but additional time would have got closer to making the purple spot invisible by bringing the inherent colours from beneath the spot through.

 

Pete.

 

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Hlarocca, this is just a shot in the dark, but the culprit could be the vented hood. Try covering the hole with a black electrical tape or any sticky opaque material that can cover the hole completely. I encountered a similar problem with my WATE with the original vented hood, although in my case the flare was always located in the lower right hand corner of the frame and it happens only in about 2% of the shots. I surmise that the vent, in extremely bright conditions,  can act like a pinhole camera and can project astray light on the surface of the front element. I have not encountered the problem after covering the vent with a black electrical tape. 

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Does it happen at low light environment?  Of course it's not supposed to be in bring sunlight neither but I am just curious.

 

I have the same lens and your post does worry me a lot.  Lately, I've discovered many Leica issues... not just product itself but also their support.  Different offices/experts tell me different stories to a specify problem, it seemed like they don't know what they are doing. 

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Hi all,

Thanks everyone for your input, and especially the touched up example from Pete, it looks much better and I appreciate you taking the time to do that. Clearly I need to do some more experimentation to determine in exactly what kind of conditions it happens and how to minimize or avoid it. I’ll try changing apertures and see how that affects it, but in my experience it’s happened all the way down to at least 5.6, but for sure it seems worse at smaller apertures. As soon as I get home this weekend I will experiment and let you know more.

 

I always use the lens hood. I haven’t tried to tape up the corner vent in the hood, the thought has also occurred to be, but I don’t think that’s the issue because it’s happened in circumstances when the sun was not on that side of the camera.

 

Jaeger,

It does not seem to happen in low light environs. Do you use your lens with an SL? Have you experienced any similar issues? I’m not worried about Leica quality as a whole, I feel they make incredibly high quality products, but I must admit to being surprised about this issue with the 24 Lux/ SL, which is why I wanted to check within the Leica community to see if anyone else is experiencing the same anomalies. I obviously can’t speak to your issues, but I’ve met mostly exceptionally professional and knowledgeable folks in my interactions with Leica staff, from Frankfurt A.M. to Seoul to Los Angeles, and quite a few places in between and I’ve been to some very extreme out of the way environments, from the Amazon in summer to Svalbard in January and I’ve never had any issues with my Leica gear, except for this one thing.

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I use the Leica M-Adapter L.

 

I just did some quick, rudimentary testing with the camera/ lens combo and noticed that as I close the aperture, the purple spot gets smaller but more intense, as if the focusing gets tighter. As I open the aperture, the spot gets larger but has less intensity. It seems as if the same amount of purple light is being diffused onto a greater area at larger aperture and focused into a smaller, tighter area as the aperture gets smaller. The spot is definitely round. Pointing towards or away from the sun or brightly lit area doesn’t seem to affect much, it is still present but perhaps changes intensity depending on ambient light conditions. Indoors or in lower overall light conditions it is less visible.

 

Also, the spot seems to almost always be there, if I focus on a dark object surrounded by a brighter area it is the most noticeable and if I then adjust focus to the brighter area it is still there but being masked slightly by the brighter light. From f16 to f5.6 it’s quite visible. At f4 it’s barely visible and at about 2.8 and larger it doesn’t seem to be visible anymore.

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Hmm... so I'm curious as to why this condition isn't seen on the M.  The explanations seem generic enough that I would have thought one might encounter this on it as well. 

 

Jaeger says he hasn't seen it on his M - that is not the same as saying it isn't seen on the M at all. "Absence of evidence is not evidence of absence."

 

BTW - I don't doubt Jaeger has not encountered it in his pictures with an M, or at least not enough to be visible (a purple spot on a purple dress?). But is that a good statistical sample across thousands of Ms and millions of pictures?

 

If I am right about the image reflecting off the shiny sensor, then off the "mirror-lens" rear lens element, into a semi-focused spot on the sensor, it will be very "subject-matter" dependent: strong subject contrast (very light and and very dark areas), as well as the exact positioning of the dark and light areas within the composition (especially related to the center of the image). As Hlarocca's pictures and description in #35 suggest. May also depend on whether the lens is focused at infinity or close-up (the rear element will move in and out and change the sharpness or diffuseness of the spot).

 

When this happened with my 75 Summicron (on an M8/9), 1) it did require strong brights and darks, and 2) a small change in composition would remove, diminish or hide the spot. I saw it almost only in the studio, with "arranged still-lifes" that included an intentionally ink-black background. It did not appear (or at least was too subtle to notice) in the other 99.99% of my 75mm Summicron pictures. Including the same studio setup with a slight change in composition. But when it happened, it happened.

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Jaeger says he hasn't seen it on his M - that is not the same as saying it isn't seen on the M at all. "Absence of evidence is not evidence of absence."

That was my first thought.  But in this  case, I refer you to the curious incident of the dog in the night. ie. despite plenty of threads here carping about the M sensor, this has never come up. I suspect you're correct, and of course, the 24 SLux is a relatively rare lens, but this is a pretty demanding lot around here. I'm surprised by the 'absence of evidence'.  

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