pack_tor Posted November 22, 2009 Share #1  Posted November 22, 2009 Advertisement (gone after registration) Hi,  Just got my M9 - loving it as my first rangefinder. However I got a couple of overexposed shots recently (my fault, i know) that's showing quite a bit of purple fringing. I'm using 50 1.4 ASPH (got it used recently). Since this is my first Leica lens/body, I'm not sure where the issue is....  Is this a lens issue? Is this a software issue ? or, Is this a sensor issue? Maybe it's not an issue at all? Am i expected to fix it in software? I was expecting the Lux to show no fringing at all considering it's regarded at the best 50 ever made - or, am i expecting too much?  The image was processed in Lightroom 3 Beta (with Brightness, Contrast and other relevant settings zeroed out. White balance is set to auto). I can eliminate it by turning "defringe" set to highlights only. If I have to correct it everytime using software, isn't there an issue somewhere ?  Please advise. I have the 100% crop + the resized image attached. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/104611-m9-50-lux-asph-too-much-purple-fringing/?do=findComment&comment=1127272'>More sharing options...
Advertisement Posted November 22, 2009 Posted November 22, 2009 Hi pack_tor, Take a look here M9 + 50 Lux Asph - Too much purple fringing?. I'm sure you'll find what you were looking for!
mjh Posted November 22, 2009 Share #2 Â Posted November 22, 2009 Purple fringing is caused by the sensor, not the lens, and there is nothing like overexposure to exacerbate the issue. No need to worry about the lens. Link to post Share on other sites More sharing options...
ulrikft Posted November 23, 2009 Share #3 Â Posted November 23, 2009 Purple fringing is caused by the sensor, not the lens, and there is nothing like overexposure to exacerbate the issue. No need to worry about the lens. Â This is.. just plain wrong. Fringing can be optical or sensor-related. This looks like optical. Link to post Share on other sites More sharing options...
mjh Posted November 23, 2009 Share #4  Posted November 23, 2009 Fringing can be optical or sensor-related. Sure enough, and there are all kinds of fringing, but purple fringing specifically is purely sensor-related, period. (There are some claiming that purple fringing is actually longitudinal chromatic aberration of the lens, but that can be refuted experimentally by showing that purple fringing can occur even in the absence of any wavelength corresponding to magenta – or blue, which together with red would also give purple/magenta.) Link to post Share on other sites More sharing options...
Rick Posted November 23, 2009 Share #5 Â Posted November 23, 2009 mjh is right. You might be able to remove it by going into LR in the detail panel and clicking on defringe. Link to post Share on other sites More sharing options...
BerndReini Posted November 23, 2009 Share #6 Â Posted November 23, 2009 The 50lux is a very sharp and contrasty lens that creates very good delineation. Since it doesn't let highlights "bleed" over into neighboring areas, this huge difference in exposure can be a problem for the sensor. In general though, I find that CA is extremely well controlled with the 50lux, much better than the Noctilux F1.0. Link to post Share on other sites More sharing options...
ho_co Posted November 23, 2009 Share #7 Â Posted November 23, 2009 Advertisement (gone after registration) pack-- You might also try another RAW processor (Capture One, for example) to prove to yourself that there's nothing wrong with your equipment. Â I've got no idea why, but some M8 shots I made had worse purple fringing than this when processed in Adobe products, but virtually none when processed in C1. Â I don't care for C1 because I don't understand it, but many people feel it does a better job. (For example, see Lightroom proponent Michael Reichmann's article, A Workflow Combining Capture One and Lightroom.) Â In addition, there have been many threads on the topic of purple fringing on the forum where you can seek solace. Â Â BTW--congratulations on both the camera and the lens! Link to post Share on other sites More sharing options...
adan Posted November 23, 2009 Share #8 Â Posted November 23, 2009 There is only one lens I own that does NOT need some kind of corrections applied "everytime using software." Â My 21 pre-ASPH (for whatever reason - it is fuzzy in the corners but almost never has color fringing, either from its own optics or the sensor. (It has the red-left issue, but that requires other techniques not available in raw processors anyway)). Â I have presets saved for all my other lenses, to fix CA, vignetting, defringing, or whatever. One click applies the preset to each image (and is probably batch-able - if I shot in batches). Link to post Share on other sites More sharing options...
C_R Posted November 23, 2009 Share #9 Â Posted November 23, 2009 Looks quite similar like my 1.5/50 CV Nokton with LR3 conversion. I tried CaptureOne V, and it was gone.... Link to post Share on other sites More sharing options...
pack_tor Posted November 23, 2009 Author Share #10 Â Posted November 23, 2009 Thanks everyone - I tried processing the image with C1. Pretty much no purple fringing. So, this can definitely be controlled using Lightroom (defringe) or C1. My only concern was if my 50 Lux or M9 are defective in any way - based on the comments here, do I assume they are normal? Link to post Share on other sites More sharing options...
jonoslack Posted November 23, 2009 Share #11 Â Posted November 23, 2009 Thanks everyone - I tried processing the image with C1. Pretty much no purple fringing. So, this can definitely be controlled using Lightroom (defringe) or C1.My only concern was if my 50 Lux or M9 are defective in any way - based on the comments here, do I assume they are normal? Â I think so - that really was a worst case kind of a scene, if you can deal with it in C1 then you're sorted (even if you want to use Lightroom most of the time). Â I've also seen fringing with my M9/50 'lux, but very rarely, and always fixable. Â Enjoy it! Link to post Share on other sites More sharing options...
marcusperkins Posted November 23, 2009 Share #12 Â Posted November 23, 2009 It probably is partially due to the lens, which is amplified by the sensor. One feeds the other. Â Shoot the same scene on film, and you will almost certainly see a similar effect. Â If it had nothing to do with the lens, why does the problem manifest itself more acutely with certain lenses? Â Canon appears to have eliminated the problem almost completely with their new 24TS lens, whereas the original version was very prone to it. This suggests (to me at least) that the lens plays a large part. Â However, as you've figured out, removal in post is largely straightforward, so nothing to worry about. Link to post Share on other sites More sharing options...
thrice Posted November 23, 2009 Share #13 Â Posted November 23, 2009 mjh, I suggest you get in touch with Eugene Hecht's publisher, as his definitive bible on optical theory and mathematics being taught in most universities disagrees with you. Â It is also one of the only english texts offering eplanations using mathematical theory for effects such as purple fringing (which he claims is caused by optics). Perhaps you can publish your own book? Since you claim purple fringing is definitively caused by the sensor, can you hypothesise why this film shot shows purple fringing? I checked your website, I'm surprised that you don't know the fundamental theory. Can you please explain the science behind sensors causing purple fringing? And if possible could you please link me to the controlled monochromatic tests that showed purple fringing occurring? Thanks. Â Here's another link to toothwalker's brilliant site with examples of longitudinal chromatic aberration causing purple and green fringing. His explanations are fully referenced to accepted textbooks, experts and manufacturers, you can use his reference list to correct those people too I assume You might struggle to correct Isaac Newton though. Â pack_tor, I think it is normal, in an overexposed scene, very few large aperture lenses exist that will preclude fringing. Link to post Share on other sites More sharing options...
jaapv Posted November 23, 2009 Share #14 Â Posted November 23, 2009 It still does not explain, Daniel, why some RAW converters are more affected than others. Link to post Share on other sites More sharing options...
thrice Posted November 23, 2009 Share #15 Â Posted November 23, 2009 Jaap I didn't try to explain it as I was only correcting the one false statement, I wasn't refuting the fact that some RAW convertors show more CA than others. In my experience this is because some RAW convertors do automatic correction for fringing. My Leica 19mm R had very mild blue/red fringing in the corners, this showed up in Lightroom and on slides but not in C1 (shot using an adapter on full frame Canon). I'm getting quite sick of misinformation on fundamentals, I may just have to do a controlled test side by side between M9 and M6 using the same lenses when I am able. But the science is on my side. Â If you have evidence to the contrary or word from the engineers please feel free to present it. Link to post Share on other sites More sharing options...
pgk Posted November 23, 2009 Share #16 Â Posted November 23, 2009 Looking at the posted picture at 100% I would say that there is just a hint of green fringing too - indicating some (albeit very little in all honesty) longitudinal chromatic aberration. But IMHO, the degree of purple fringing is more significant which I would suggest may be down to the sensor. So, as ever, its not necessarily as simple as just one straightforward cause. Â FWIW my 24/1.4 MkI Canon lens exhibits what I think must be substantial longitudinal chromatic aberrations wide open, as it produces green fringing on out-of-focus high contrast edges behind the point of focus and purple fringing on high contrast edges in front of the point of focus - clearly this cannot be a sensor problem. I think that the purple is sometimes more evident (on more contrasty subject matter) so I suspect that under certain circumstances there are sensor derived problems too, which makes sense. I use my 50 asph on my cropped sensor M8 and have never had any problems with fringing even wide open. As the M9 utilises its full frame capability it seems able to show up what very marginal chromatic problems still persist in the very corner of the frame although from the picture posted I'd say that they really are very marginal indeed Link to post Share on other sites More sharing options...
jaapv Posted November 23, 2009 Share #17 Â Posted November 23, 2009 Jaap I didn't try to explain it as I was only correcting the one false statement, I wasn't refuting the fact that some RAW convertors show more CA than others. In my experience this is because some RAW convertors do automatic correction for fringing. My Leica 19mm R had very mild blue/red fringing in the corners, this showed up in Lightroom and on slides but not in C1 (shot using an adapter on full frame Canon). I'm getting quite sick of misinformation on fundamentals, I may just have to do a controlled test side by side between M9 and M6 using the same lenses when I am able. But the science is on my side. Â If you have evidence to the contrary or word from the engineers please feel free to present it. Daniel, I do not dispute that a lens can have longitudinal CA resulting in purple fringing, but as I understand it the interpretation of the bayer pattern on high-contrast edges can, depending on the algorithm used, also lead to this effect. It will be very interesting to see a film-sensor comparison to the determine the exact cause for this lens, or, maybe , the proportion in which each possible cause is responsible. Link to post Share on other sites More sharing options...
Rick Posted November 23, 2009 Share #18 Â Posted November 23, 2009 pack_tor, I forgot to mention that when I got my M8 I bought the 50/1.4 Asph like you and after a few months I saw the fringing in some pictures and not know what it was, I assumed I might have a bad copy of the lens. Tony at PopFlash sent me a new 50/1.4 and let me compare. I could not tell the difference between the two lenses so I sent the newer one back to him (nice guy). Â It was much later that I discovered the defringe feature in LR and recognized that this was what I was seeing. I would say that I can duplicate the effect on several lenses I have. It is easiest to see with a cloudy background through the trees. Anyway, I just wanted to say, it is not your copy of the lens, mine does it too and so did the second copy I tested. Link to post Share on other sites More sharing options...
tgray Posted November 23, 2009 Share #19 Â Posted November 23, 2009 Here's another link to toothwalker's brilliant site with examples of longitudinal chromatic aberration causing purple and green fringing. His explanations are fully referenced to accepted textbooks, experts and manufacturers, you can use his reference list to correct those people too I assume You might struggle to correct Isaac Newton though. Â If that was the source of the purple fringing in this case, one should be able to construct a scenario where you can get only green fringing too. It's quite possible that the source of the fringing is from this, though I've read a quote from the designer of this lens that it is an APO design. Â Can't one test longitudinal chromatic aberration by focusing on a rule printed in black on white paper, set at an oblique angle to the camera? You should see purple fringing on one side of the focal point and green on the other. I'm sure there are other test for LCA that once could run on this lens. Â I've read that purple blooming such as this (on sensors) can be caused by chromatic aberration, not of the lens, but of the microlenses on the sensor. If true, it would make it a sensor specific phenomena. As would de-bayering the raw data. I'm not sure if either of those are effects in the real world, but on the surface, they are plausible. Â Again, while this example could be from LCA in the lens, it could be from other sources. Just because the evidence in one example (toothwalker, your film shot) matches one explanation (LCA) does not mean that that explanation is the correct one here. Link to post Share on other sites More sharing options...
Philip Freedman Posted November 23, 2009 Share #20 Â Posted November 23, 2009 My 50 1.4 ASPH also shows purple fringing in backlit situations. My old 1970's 50 f2 Summicron 11817 is much better ! Â Philip Link to post Share on other sites More sharing options...
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