lct Posted March 24, 2015 Share #141 Posted March 24, 2015 Advertisement (gone after registration) So blue, red and/or magenta fringing invisible on film and deriving from lenses having little CA, if any, like apo lenses should be attributed mainly to the CA of said lenses instead of digital sensors according to you, do i understand you right? Link to post Share on other sites More sharing options...
Advertisement Posted March 24, 2015 Posted March 24, 2015 Hi lct, Take a look here Is this CA problem on my 50/1.4 ASPH, it's normal or not?. I'm sure you'll find what you were looking for!
Jeff S Posted March 24, 2015 Share #142 Posted March 24, 2015 Where is 01af? Jeff Link to post Share on other sites More sharing options...
CheshireCat Posted March 24, 2015 Share #143 Posted March 24, 2015 So blue, red and/or magenta fringing invisible on film and deriving from lenses having little CA, if any, like apo lenses should be attributed mainly to the CA of said lenses instead of digital sensors according to you, do i understand you right? Yes. And digital sensors make CA more visible than on film. Link to post Share on other sites More sharing options...
pgk Posted March 24, 2015 Share #144 Posted March 24, 2015 That is not really what we are discussing here... Wrong. This isn't actually a discussion is it;)! Link to post Share on other sites More sharing options...
lct Posted March 24, 2015 Share #145 Posted March 24, 2015 Yes.And digital sensors make CA more visible than on film. So given that the 50/2 apo shows the stronger purple fringing, either it is not a true apo lens, or the smaller the CA the higher the CA sort of... Hard to follow you i must say. Link to post Share on other sites More sharing options...
CheshireCat Posted March 24, 2015 Share #146 Posted March 24, 2015 So given that the 50/2 apo shows the stronger purple fringing, either it is not a true apo lens, or the smaller the CA the higher the CA sort of... Hard to follow you i must say. APO correction performance is specified in the field of focus. You will have much bigger error in out-of-focus details (i.e. branches in this case). Besides, even APO lenses better corrected than the APO Summicron (like the Otus 55) are not perfect and can show CA if you do your best to provoke it. Your APO Summicron is a great lens, but it is not perfect. Sorry. Finally, digital sensor being sensitive to frequencies outside of visible light make this issue much more visible. If anyone here can prove the sensor is the cause, please post your shots and prove me wrong. But please spare posting links to the usual, popular, Internet myths. Link to post Share on other sites More sharing options...
CheshireCat Posted March 24, 2015 Share #147 Posted March 24, 2015 Advertisement (gone after registration) Wrong. This isn't actually a discussion is it;)! Not much, especially because of people like you. I asked you a question twice, and I am still waiting for an answer. If you can not contribute to the discussion, then at least spare your sarcasm. Link to post Share on other sites More sharing options...
thighslapper Posted March 24, 2015 Share #148 Posted March 24, 2015 So given that the 50/2 apo shows the stronger purple fringing, either it is not a true apo lens, or the smaller the CA the higher the CA sort of... Hard to follow you i must say. I have popped in to see if there is any more sense to this 'discussion' ...... alas .... no ... I suggest you give up LCT CC will argue black is white, no matter what you say, slag off everything produced to counter his views and produce the same dodgy 'evidence' to support his own. The position is still EXACTLY as I stated here ........http://www.l-camera-forum.com/leica-forum/leica-m-lenses/366748-ca-problem-my-50-1-4-a.html#post2905288 And CC has still not explained how the aberration in my photo here http://www.l-camera-forum.com/leica-forum/leica-m-lenses/366748-ca-problem-my-50-1-4-a-3.html#post2906298 is explained by CA alone. The digital camera and lens is a complex system with a variety of interacting variables that produces different results depending on an equally complex mix of circumstances. There is no simple single answer to the some of the 'aberrations' produced on a digital image. Using a medical analogy, purple fringing is a 'syndrome' with a recognisable mixture of symptoms, underpinned by a selection of pathological processes, but no single disease per se. I've spent my life working with uncertainty and managing the unpredictable and poorly understood ..... and learnt very long ago that sometimes you just never get a definitive answer .... and just get on with dealing with it rather that worrying about 'why ?' ... Link to post Share on other sites More sharing options...
CheshireCat Posted March 24, 2015 Share #149 Posted March 24, 2015 The position is still EXACTLY as I stated here ........http://www.l-camera-forum.com/leica-forum/leica-m-lenses/366748-ca-problem-my-50-1-4-a.html#post2905288 Please provide the raw file, so I can check it in more detail and tell you more. And CC has still not explained how the aberration in my photo here http://www.l-camera-forum.com/leica-forum/leica-m-lenses/366748-ca-problem-my-50-1-4-a-3.html#post2906298 is explained by CA alone. I have. You probably missed my post. It is now your turn to explain it in terms of sensor issues... but I have a feeling you will not even try . It is easy to criticize other people, much harder to contribute with your own efforts. Using a medical analogy, purple fringing is a 'syndrome' with a recognisable mixture of symptoms, underpinned by a selection of pathological processes, but no single disease per se. You cannot compare purple fringing to human pathology, the latter being orders of magnitude more complex. I've spent my life working with uncertainty and managing the unpredictable and poorly understood ..... and learnt very long ago that sometimes you just never get a definitive answer .... and just get on with dealing with it rather that worrying about 'why ?' ... I don't know what your job is/was, but I am sure someone will eventually understand what you couldn't. Someone with a different approach. Link to post Share on other sites More sharing options...
lct Posted March 25, 2015 Share #150 Posted March 25, 2015 [...] If anyone here can prove the sensor is the cause, please post your shots and prove me wrong. But please spare posting links to the usual, popular, Internet myths. There is no such thing as "the" cause in causality chains by definition. I don't know whether it is a primary cause or not but the simple fact that PF is only visible on digital pictures is the best evidence that it is a "unique phenomenon on digital sensors" as Cambridge in Colour says with good sense IMHO. Link to post Share on other sites More sharing options...
CheshireCat Posted March 25, 2015 Share #151 Posted March 25, 2015 There is no such thing as "the" cause in causality chains by definition. "The" cause is the primary cause, the one that is at the origin of the casuality chain. E.g. If a guy kicks a dog in the nuts and the dog bites him, the cause of the "accident" is not the dog I don't know whether it is a primary cause or not but the simple fact that PF is only visible on digital pictures is the best evidence that it is a "unique phenomenon on digital sensors" as Cambridge in Colour says with good sense IMHO. We all agree that digital sensors (wider spectral sensitivity), digital processing (such as pushing exposure and shadows) and digital pixel peeping (1:1 detail enlargements) can make CA much more noticeable than it was when we used to shoot film. But CA is the primary cause. I am sure we can find purple/violet/blue fringing examples on high-resolution film, properly processed and abnormally enlarged to digital-like pixel-peeping levels. But this requires some effort that no one blaming digital sensors and software processing is probably willing to make. Link to post Share on other sites More sharing options...
lct Posted March 25, 2015 Share #152 Posted March 25, 2015 "The" cause is the primary cause, the one that is at the origin of the casuality chain. E.g. If a guy kicks a dog in the nuts and the dog bites him, the cause of the "accident" is not the dog  The dog is the immediate cause and his owner will be sued if it did not wear a muzzle while it had to. There is not one cause, hence no "the" cause, here and elsewhere, when there are many. Again, there is a combination of causes explaining PF more or less perfectly. One of these causes is the digital sensor for the simple reason that PF does not appear elsewhere, i won't repeat the obvious. As for the respective roles of sensor, CA or anything else in the causality chain, i leave this interesting matter to more competent colleagues than this modest lawyer. Link to post Share on other sites More sharing options...
pgk Posted March 25, 2015 Share #153 Posted March 25, 2015 If you can not contribute to the discussion, then at least spare your sarcasm. As I said Cheshire Cat this is not a discussion. You are now trying to promote a viewpoint as fact and many of us do not agree with the viewpoint, let alone believe it to be a fact. FWIW I have examined a lot of files from various lenses and cameras and I am of the opinion that there is not always a single simple cause of purple fringing. In some cases there is undoubtedly an element of CA, but in others there appears to be none at all. I could spend hours cropping images, testing and explaining but I won't because its too time cosuming and still 'proves' nothing, doing so would merely reinforce my own conclusions. I'm trying not to be personal and I do not have to 'prove' anything here on the forum - most people can read threads and then make informed decisions for themselves. But trying to promote an 'absolute', as you are, when many of us disagree is a very effective way of putting people's backs up and, as you must be aware by now, your arguments are not considered conclusive and you simply cannot 'prove' your point. If you persist in doing so then fair enough, carry on, but if you bothered to read other people's posts and opinions instead of being so fixed in your own opinion, you might just realise that others have useful information to contribute too. Link to post Share on other sites More sharing options...
jaapv Posted March 25, 2015 Share #154 Posted March 25, 2015 I am sure we can find purple/violet/blue fringing examples on high-resolution film Show.... Link to post Share on other sites More sharing options...
Peter Branch Posted March 25, 2015 Share #155 Posted March 25, 2015 ........I am sure we can find purple/violet/blue fringing examples on high-resolution film, properly processed and abnormally enlarged to digital-like pixel-peeping levels......... Does it need to be colour film ? One could use panchromatic microfilm with filters and compare the images. However, setting such an esoteric, but entirely possible, procedure aside lets assume we are dealing with colour film. It is often assumed/stated/reported that, of relatively modern films colour films, Kodachrome 25 had the highest resolution. Actually the relatively short lived Kodak Ektar 25 colour negative film had higher resolving power. All I can contribute to this subject is that having spent many hours looking at images taken on Kodachrome 25 and Ektar 25 films, both optically and via scans, I have never encountered anything resembling the "Blooming" effect which is the subject of this thread. CA can be detected in some circumstances and it is true to say that lenses known to be highly corrected for CA do produce "Sharper" edges, but these edges never show the blooming effect. I conclude that the effect is definitely a characteristic of digital sensors since it can be induced in every digital sensor of which I'm aware. It may be exacerbated by different lenses but the degree of CA correction does not seem to correlate with the observed effect. Link to post Share on other sites More sharing options...
CheshireCat Posted March 25, 2015 Share #156 Posted March 25, 2015 Show.... Scroll down to the last set of pictures here: Chromatic aberrations Purple fringing on film. This should close the discussion for good. Link to post Share on other sites More sharing options...
Peter Branch Posted March 25, 2015 Share #157 Posted March 25, 2015 Scroll down to the last set of pictures here:Chromatic aberrations Purple fringing on film. This should close the discussion for good. Just like I said; CA can be detected on film - but the examples you cite are not blooming as seen on digital sensors. The caption clearly states that they are CA. There are other characteristics, such as the "complimentary colours" on either side of the image, that point to this being classical CA. So the discussion is not closed for good. Link to post Share on other sites More sharing options...
CheshireCat Posted March 25, 2015 Share #158 Posted March 25, 2015 Just like I said; CA can be detected on film - but the examples you cite are not blooming as seen on digital sensors. The caption clearly states that they are CA. Yes. CA is the only cause of purple fringing. This example was to debunk the myth that "purple fringing does not happen on film". There are other characteristics, such as the "complimentary colours" on either side of the image, that point to this being classical CA. Complementary colors are visible in the lateral CA example (first image on the left), as expected. Only purple fringing is present in the central image showing longitudinal CA, which looks just like what you call "digital sensor blooming" and you said you had never seen anything like that on film. So the discussion is not closed for good. Allright. Feel free to bring UFOs, phantoms and superheroes into the discussion. Let's have some more fun ! Link to post Share on other sites More sharing options...
Doc Henry Posted March 25, 2015 Share #159 Posted March 25, 2015 Scroll down to the last set of pictures here:Chromatic aberrations Purple fringing on film. This should close the discussion for good. On your link "Chromatic aberrations recorded on film. The church cross is photographed off a slide projection screen" Cheshire possible because of the projection lamp ! Same reason on flatbed scan (or another scan) then reproduced in digital Best Henry Link to post Share on other sites More sharing options...
CheshireCat Posted March 25, 2015 Share #160 Posted March 25, 2015 On your link "Chromatic aberrations recorded on film. The church cross is photographed off a slide projection screen" Cheshire possible because of the projection lamp ! Same reason on flatbed scan then reproduced in digital Best Henry Good points. I knew someone would come up with this The image on the left shows lateral CA. If the cause was an incredibly crappy slide projector, all photos made with any lens would be affected in the same manner. A trivial condition to detect, especially for a savvy guy like the author of that article. The central and right image show same subject shot twice (slightly different focus distance). If the scanner sensor was the cause, then they would both show the same kind of fringing. Instead, one shows purple fringing and the other green fringing (complementary colors), proving this is caused by longitudinal CA captured on film. That is equivalent to what I showed on CMOS in my palm trees shot. Link to post Share on other sites More sharing options...
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