Pindy Posted February 3, 2011 Share #1 Posted February 3, 2011 Advertisement (gone after registration) Check out the purple fringes I've been getting in high contrast. The lens is a 35mm Summilux ASPH (previous edition). Is this normal for this lens? Having shot the last year and a half with this lens on an M6 with B&W, I can't say I've seen anything like it, neither with any Canon L or Nikon lens I've ever shot with: No amount of defringing or CA adjustment in LR3 (or in my demo of Capture One) seems to make any difference. I suppose I expected a little better performance from such a highly regarded lens. Link to post Share on other sites More sharing options...
Advertisement Posted February 3, 2011 Posted February 3, 2011 Hi Pindy, Take a look here Is this an inordinate amount of CA?. I'm sure you'll find what you were looking for!
3rdtrick Posted February 3, 2011 Share #2 Posted February 3, 2011 How far did you drill into the image? I have noticed things with the M9 images that I never saw before because I am able to drill into them farther than ever before. My 35 is a pre-ASPH so I cannot compare but I am sure others on here can. Pete Link to post Share on other sites More sharing options...
Pindy Posted February 3, 2011 Author Share #3 Posted February 3, 2011 How far did you drill into the image?I have noticed things with the M9 images that I never saw before because I am able to drill into them farther than ever before. My 35 is a pre-ASPH so I cannot compare but I am sure others on here can. Pete That is a 100% crop. You can see it at nearly any magnification. Link to post Share on other sites More sharing options...
adan Posted February 3, 2011 Share #4 Posted February 3, 2011 Well, you've nuked the sensor with gross overexposure of those areas that are fringing. Even the highlights on the columns are blown out to white, let alone the light sources. Pour too much light onto a sensor, and you will get both optical flare from light diffused and reflected within the cover glass/IR filter, and electronic "blooming" from excess electrons spilling into neighboring pixels. So I can't really tell anything about the lens performance from this image. Were the Canons and Nikkors you used also f/1.4 35mms? Link to post Share on other sites More sharing options...
01af Posted February 3, 2011 Share #5 Posted February 3, 2011 At the given magnification, I cannot see the slightest amount of chromatic aberration in your image. Link to post Share on other sites More sharing options...
3rdtrick Posted February 3, 2011 Share #6 Posted February 3, 2011 I looked at a few from my pre-A lux and even wide open they do not seem that bad. I usually shoot at F2 unless I am looking for a specific look. Hopefully someone with the ASPH will make a comparison. Pete Link to post Share on other sites More sharing options...
Pindy Posted February 3, 2011 Author Share #7 Posted February 3, 2011 Advertisement (gone after registration) At the given magnification, I cannot see the slightest amount of chromatic aberration in your image. I am obviously mis-speaking. Link to post Share on other sites More sharing options...
Pindy Posted February 3, 2011 Author Share #8 Posted February 3, 2011 Well, you've nuked the sensor with gross overexposure of those areas that are fringing. Even the highlights on the columns are blown out to white, let alone the light sources. Pour too much light onto a sensor, and you will get both optical flare from light diffused and reflected within the cover glass/IR filter, and electronic "blooming" from excess electrons spilling into neighboring pixels. So I can't really tell anything about the lens performance from this image. Were the Canons and Nikkors you used also f/1.4 35mms? Well I'm damned if I do or don't. Given how fussy the M9 sensor is about underexposure (banding, noise, weird colors) I'm loathe to give it anything other than a healthy amount of open shutter. Do that, and lights turn ugly... and purple. Link to post Share on other sites More sharing options...
3rdtrick Posted February 3, 2011 Share #9 Posted February 3, 2011 Thank you Andy, I think we all learned something today... Pete Link to post Share on other sites More sharing options...
Washington Posted February 3, 2011 Share #10 Posted February 3, 2011 Looks to me like a perfect candidate for HDR..... which IS quite useful at times and you can make it look "real" with the right adjustments. I am not a fan of those "psychedelic" HDR's. Link to post Share on other sites More sharing options...
Pindy Posted February 3, 2011 Author Share #11 Posted February 3, 2011 So I can't really tell anything about the lens performance from this image. Were the Canons and Nikkors you used also f/1.4 35mms? Yes, and similar focal lengths in others. I expect a little trouble, but usually not at this level. Link to post Share on other sites More sharing options...
Pindy Posted February 3, 2011 Author Share #12 Posted February 3, 2011 Looks to me like a perfect candidate for HDR..... which IS quite useful at timesand you can make it look "real" with the right adjustments. I am not a fan of those "psychedelic" HDR's. This brings up an interesting idea for a test. If the effect is only in extreme overexposure, that would corroborate Andy's notion of it being just what happens to a sensor—which I don't dispute—but it would be nice for me to discover that my lens is not the culprit. Link to post Share on other sites More sharing options...
adan Posted February 4, 2011 Share #13 Posted February 4, 2011 Keep in mind that the M9's LCD is rather dark, and especially blocks up the shadows. So a "good" exposure may look quite dark on the back of the camera (but will open up a lot on the computer). However, shooting at night makes the LCD look pretty bright to dark-adapted eyes, so in this particular situation that may not apply. This is a situation where I'd probably bracket exposures (whether I was going to do HDR or not) - digital is more like exposing slide film than exposing B&W negs in an M6. At any rate, this is not classical lens-based CA, which would tend to show green on one side of objects and purple on the other (or other pairings of complementary colors - red/cyan or yellow/blue). EDIT: cf: http://www.l-camera-forum.com/leica-forum/digital-forum/145063-what-chromatic-aberrations-really-look-like.html Link to post Share on other sites More sharing options...
ho_co Posted February 4, 2011 Share #14 Posted February 4, 2011 This is an aspect of digital photography known as "purple fringing." (Use the Forum's search function to look up a number of posts on the same topic.) Since the effect is related to the sensor's processing characteristics, you won't see it if you shoot the same lens on film. Other cameras also show it to varying degrees in similar conditions. Link to post Share on other sites More sharing options...
Pindy Posted February 4, 2011 Author Share #15 Posted February 4, 2011 This is an aspect of digital photography known as "purple fringing." (Use the Forum's search function to look up a number of posts on the same topic.) Since the effect is related to the sensor's processing characteristics, you won't see it if you shoot the same lens on film. Other cameras also show it to varying degrees in similar conditions. Though "purple" and "fringes" were the 4th and 5th words of my original post, I wasn't aware until now that they were not of the same type of artifacts as CA. Some reading up would be good. Link to post Share on other sites More sharing options...
ho_co Posted February 4, 2011 Share #16 Posted February 4, 2011 Believe me, we've all learned because of posts like yours. And no one had heard of "purple fringing" before we started seeing it on digital sensors. Some of the threads on the topic grew pretty long as we gradually started to get it sorted out. It was after one of them that Andy posted his "What CA really looks like" thread. Digital has meant a lot of learning, particularly for those of us who thought we knew our way around the 'classical' aspects of photography. Link to post Share on other sites More sharing options...
Washington Posted February 4, 2011 Share #17 Posted February 4, 2011 Give HDR a shot and see what happens. I don't think it's your lens at all. The subject is a tough customer! Link to post Share on other sites More sharing options...
lars_bergquist Posted February 4, 2011 Share #18 Posted February 4, 2011 It seems to me that you should check the histogram of the original file, if you still have it. There is probably lots of exposure slammed tight into the right end of the graph, indicating that the sensor has got lots more light than it can handle. Making a test exposure and checking the histogram is the best exposure meter there is. Ideally, nearly the whole exposure range should be shown on the graph line, with just a minimal amount of "abutting" on the shadow side to ensure good blacks, and none on the highlight side. The histogram is an education in itself. I learned more about exposure after the advent og the M8 than I learned in the preceding fifty years – and I spent some of those years in darkrooms! The old man from the Age of Hypo (not Hype) Link to post Share on other sites More sharing options...
250swb Posted February 4, 2011 Share #19 Posted February 4, 2011 Pindy, it may be worth thinking about how you meter the scene along with the other useful advice already given. Your Nikon or Canon lenses are probably used on cameras where you have multi pattern metering modes enabled, so the exposure is more accurate across the overall scene. If I use my imagination to construct your full size image the Leica meter will act more like a spot meter in that situation, it won't take much movement of the camera one way or another to go from reading off a shadow to reading off a highlight. So you need to find an average area to meter off, and use your camera in manual mode so any slight movement of the meter over a shadow or highlight area isn't going to throw the whole exposure off. But you may be doing this anyway. Andy's point about the M9 LCD being 'dull' is a good one, its not a great indication of exposure, more for checking composition. But if you use it with the histogram you are using facts for choosing your exposure, not guesswork. Steve Link to post Share on other sites More sharing options...
01af Posted February 4, 2011 Share #20 Posted February 4, 2011 ... it would be nice for me to discover that my lens is not the culprit. So be reassured: The lens is not the culprit. I'm not saying the Summilux-M 35 mm Asph was totally free of chromatic aberration. But its usual level of CA is very low, and no CA is visible in your sample image shown above. As others already have stated, the fringes purely are a sensor issue that comes from vastly over-exposed highlights. Possibly the aperture being wide open also adds to the effect—but even then, it still is not a lens issue but an interaction between the photosites and the width of the incoming light cones. Try a smaller aperture; it might help (but mostly likely won't solve the issue entirely). On film and with a subject like that, you'd run into the same kind of problems basically; it just would look differently. The highlights would also be burnt out and spill over in the adjacent areas—only the spills would look white, not violet, and hence appear less objectionable. It's not too hard to de-colourise or de-saturate those digital fringes in post-processing. Link to post Share on other sites More sharing options...
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