CheshireCat Posted March 28, 2015 Share #201 Posted March 28, 2015 Advertisement (gone after registration) Nokton 1,1/50:Planar 2,0/50: Thanks. The Planar shots are a nice and clear examples of Longitudinal CA. It is very easy to notice that objects in front of the focus field have purple fringing, while objects behind the focus field have a complementary green/cyan fringing (clearly visible in one of the wires). Again, it would not make any sense for a sensor to treat objects behind the focus field in a different way than objects in front. The Nokton also shows Lateral CA, and this is why you see some purple also behind the focus field at the edge of the frame. Link to post Share on other sites More sharing options...
Advertisement Posted March 28, 2015 Posted March 28, 2015 Hi CheshireCat, 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!
Nordvik Posted March 28, 2015 Share #202 Posted March 28, 2015 Ok. But what about this? 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/242349-is-this-ca-problem-on-my-5014-asph-its-normal-or-not/?do=findComment&comment=2788635'>More sharing options...
CheshireCat Posted March 28, 2015 Share #203 Posted March 28, 2015 Ok. But what about this? Same explanation I gave for thighslapper's shot. And, if the problem was the sensor, wouldn't you expect to see purple also along the red object ? Link to post Share on other sites More sharing options...
adan Posted March 28, 2015 Share #204 Posted March 28, 2015 I think there are no dummy people here. Just people who are not informed enough... Well, it's nice of you to SAY so - but from many of your other statements, you clearly do think most people here are at least dumber than you are, and need educating (preferably - apparently - in an obnoxious and condescending way). Cheshire Cat, Here is Your Life (on this thread, anyway...) "Sorry, but what you and Andy think is not going to demonstrate anything." "You probably need an eye doctor...." "How sad is your attitude. You don't even know the definition of "faith"." "That BS does not match your experience......" "I am afraid that this "reliable" source is laughably wrong." "Can't wait to be enlightened by your knowledge :)" "All your three sentences are false. Perhaps you should read posts more carefully." "thighslapper, [sigh] you are embarrassing yourself..." In case you still haven't figured it out - these are why pop handed you 8840 words of the forum rules. There is no objective evidence that you are in any way qualified to lecture others on this or any other subject. You are just one more forum member. There is a fair amount of objective evidence that you are rather arrogant, rude and condescending. Which in itself is also evidence that you are not particularly "smart" - regardless of your knowledge or IQ. "Smart" people can persuade others - arrogant, condescending rude people never persuade others, because they themselves become the issue. (Been there, done that, try to avoid wearing that t-shirt these days). _______________ Now - back to substance. I think there has been a bit of talking at cross-purposes, due to a misunderstanding of the definition of Chromatic Aberration. For convenience, here is Wikipedia's definition - but everyone is free to seek out other sources. "Chromatic aberration (CA, also called achromatism, chromatic distortion, and spherochromatism)..... is a failure of a lens to focus all colors to the same convergence point." Note particularly the underlined words - "focus" and "convergence point." Color fringes in out-of-focus areas are NOT chromatic aberrations - not longitudinal, not lateral. They are NOT at the focus or convergence point - therefore they are as undefined as is "n divided by zero". And indeed - you are correct that any lens can, and most if not all do, produce tinted blurs/fringes of complementary colors in front of and behind the plane of focus. Including APO lenses - see attached. And that that does not necessarily have anything to do with sensors. Where you are incorrect is in your creation of a "CheshireCat dictionary" that defines color fringes outside the focus plane as CA. They simply are not CA, by the objective standards of physics and the optics industry. If you believe otherwise, please provide a source that supports your own definition unequivocally. As Mark Twain said: "It's ain't what you don't know that gets you into trouble - it's what you know for sure, that just ain't so." _______ Moving along - MY comments regarding purple fringing precisely and soley applied to the purple fringes that occur IN the plane of focus, and that do not resemble long. CA (as previously posted) because they appear in high-contrast edges, while long. CA LOWERS contrast, among other things. These CAN be caused by long. CA, in whole or in part - but that is not the same as saying - or proving - that they can ONLY be caused by CA, in all cases. You claim that CA is the only source of purple fringing in the plane of focus. You have not demonstrated your claim with evidence. 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/242349-is-this-ca-problem-on-my-5014-asph-its-normal-or-not/?do=findComment&comment=2788727'>More sharing options...
CheshireCat Posted March 29, 2015 Share #205 Posted March 29, 2015 Thanks Andy. I think some of my sentences you cited are arrogant, and I take full responsibility. I think hypocrisy is part of the reason why this world is far from perfect, so I try to always speak my mind at the cost of being perceived as rude (maybe it is what I actually am). I appreciate you telling me what you really think. I take it as a gift. I don't need to persuade anyone. I don't need followers. --- Back to the subject, my definition of CA is more generic than what you'll find in most dictionaries. "Ab errare" in Latin means "to wander away from" which is actually what the different light frequencies do when they are refracted. The "mechanism" is the same in and out of the focus "plane", so you will agree that this is just a formalism. Besides, there is nothing like a single "focus plane"; not even for so-called APO lenses. If you have an alternative, more precise term for CA outside of the "focus plane", just let me know and I will comply. I still "arrogantly" claim the only reason (i.e. "primary cause in the casuality chain") for purple fringing is the lens. If anyone thinks there are other primary causes, please post your shots and reasoning. I salute you with this TIE Fighter. 50mm@f/0.92. There are many interesting optical aberrations at play. 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/242349-is-this-ca-problem-on-my-5014-asph-its-normal-or-not/?do=findComment&comment=2788874'>More sharing options...
jankap Posted March 29, 2015 Share #206 Posted March 29, 2015 ..... Makes sense, but unfortunately the opposite condition of "CA" is "no CA", and there are no lenses that have "no CA". ..... I think the "branches against the sky" and the "sunspot in a window frame" are not much different. Both involve a relatively dark out of focus object against a very bright background. If a lens does not receive "blue" light. It cannot refract it. So if you could produce 2 pictures one with blue light in the spectrum and the other one without, you could prove, that it is the lens. White balance is a problem, the amount of light is something to think over. Also, a forum member (could not find the post now) answered, that a UV filter does not help. Perhaps here too the comparison with/without filter would be interesting. If the sensor records "blue", when there is no blue light available, we would have to think over again. Jan Link to post Share on other sites More sharing options...
jaapv Posted March 29, 2015 Share #207 Posted March 29, 2015 Advertisement (gone after registration) That is an interesting thought, Jan. Now if somebody could produce magenta fringing using a green filter... Link to post Share on other sites More sharing options...
Peter Branch Posted March 30, 2015 Share #208 Posted March 30, 2015 ...........Also, a forum member (could not find the post now) answered, that a UV filter does not help. .......... It would be something of a surprise if a UVa filter did have any effect as all current, and many older, Leica lenses have a built in UVa filter usually in the "cement" of one of the groups. In the past, (post c1960), Leica advertised the use of its patented Absorban cement, which replaced Canada Balsam, to eliminate UV transmission but I have not seen the term used for many years. Link to post Share on other sites More sharing options...
pgk Posted March 30, 2015 Share #209 Posted March 30, 2015 It would be something of a surprise if a UVa filter did have any effect as all current, and many older, Leica lenses have a built in UVa filter usually in the "cement" of one of the groups. In the past, (post c1960), Leica advertised the use of its patented Absorban cement, which replaced Canada Balsam, to eliminate UV transmission but I have not seen the term used for many years. FWIW I just had the rear group on a v.4 35mm Summicron re-cemented as they had split apart. The comment that came back from the guy who actually re-aligned and cemented the two glass elements together was that the elements themselves were of high UV absorbency and it required a substantial dose of UV to cure the new cement as a result. So these elements do transmit UV but obviously at relatively low levels. Link to post Share on other sites More sharing options...
Exodies Posted March 30, 2015 Share #210 Posted March 30, 2015 That is an interesting thought, Jan. Now if somebody could produce magenta fringing using a green filter... Not going to be easy as the filter needs to be behind the lens. How about using a pinhole? Link to post Share on other sites More sharing options...
CheshireCat Posted March 30, 2015 Share #211 Posted March 30, 2015 How about using a green laser ? http://www.l-camera-forum.com/leica-forum/1741470-post68.html NOTE: Don't try this at home. Lasers could damage your sensor. Link to post Share on other sites More sharing options...
Erik Gunst Lund Posted March 30, 2015 Share #212 Posted March 30, 2015 This post clearly shows Purple Fringing on film! I have shot many Leica M mount lenses and hundreds of Nikkor F lenses film and digital - Some lenses show more PF than others but with a little care it's easily removed in PP Just make sure not to induce other artifacts as you move those sliders in PP! Great thread! - Now I will go and shoot some images Link to post Share on other sites More sharing options...
jankap Posted March 30, 2015 Share #213 Posted March 30, 2015 Not going to be easy as the filter needs to be behind the lens. The lens does not produce blue spectrum by itself. Sunlight (all wavelengths) comes in, the visible part + IR and somewhat UV are refracted and lead to the sensor. The original question was: "Is this a CA problem on my 50/1.4 ASPH?". To answer the question "lens or sensor?" it would be interesting to see, what the lens does without the blue spectrum. Same picture with and without. Differential diagnostics so to say. The light coming from one "point" of the sharpness plane should come to one "point" of the sensor. Alas the lens tends to refract wavelengths differently. Achromatic, APO and nonAPO lenses are designed differently. But other than the design of audio amplifiers - flat from 10 Hz to 20.000 Hz - these lens types are optimized for 1, 2 or 3 wavelengths only (of course without peaking). And there is no band pass filter. So UV and IR can play for themselves. Jan Link to post Share on other sites More sharing options...
BerndReini Posted March 30, 2015 Share #214 Posted March 30, 2015 This post clearly shows Purple Fringing on film! This thread is making my head spin. I just clicked the link to the other post, and now I am even further from having the correct answer to what causes purple fringing. It seems that very knowledgeable people including lens and sensor designers are trying to figure this out. Bottom line is that purple fringing does exist and it is to some extent lens dependent. The 50 lux aspherical shows more of it than the 50 Apo, my Noctilux f1 shows even more. And this holds true when they ere stopped down to the same f stop. The aperture definitely does affect it, but I am not sure whether depth of field alone makes the difference since small sensor point and shoots show more extreme purple fringing than our full-frame Leicas. Sean Reid tests purple fringing as one of his criteria and some Zeiss lenses perform really well. I don't like purple fringing and I try to avoid it whenever I can, correct for it in post carefully whenever I can't. It is a consideration for my choice of lenses, which is why I avoid the Noctilux when shooting color in bright sunlight for the most part, but then again other considerations are more important to me. If someone designs a less that shows no purple fringing, I'll be happy to consider it. The Sony 55 1.8 on the A7 shows a lot of purple fringing despite being slower than the 50 lux and significantly bigger. Of course it is also a lot cheaper. Link to post Share on other sites More sharing options...
jdlaing Posted March 30, 2015 Share #215 Posted March 30, 2015 This thread is making my head spin. I just clicked the link to the other post, and now I am even further from having the correct answer to what causes purple fringing. It seems that very knowledgeable people including lens and sensor designers are trying to figure this out. Bottom line is that purple fringing does exist and it is to some extent lens dependent. The 50 lux aspherical shows more of it than the 50 Apo, my Noctilux f1 shows even more. And this holds true when they ere stopped down to the same f stop. The aperture definitely does affect it, but I am not sure whether depth of field alone makes the difference since small sensor point and shoots show more extreme purple fringing than our full-frame Leicas. Sean Reid tests purple fringing as one of his criteria and some Zeiss lenses perform really well. I don't like purple fringing and I try to avoid it whenever I can, correct for it in post carefully whenever I can't. It is a consideration for my choice of lenses, which is why I avoid the Noctilux when shooting color in bright sunlight for the most part, but then again other considerations are more important to me. If someone designs a less that shows no purple fringing, I'll be happy to consider it. The Sony 55 1.8 on the A7 shows a lot of purple fringing despite being slower than the 50 lux and significantly bigger. Of course it is also a lot cheaper. Purple fringing - Wikipedia, the free encyclopedia Link to post Share on other sites More sharing options...
lct Posted March 30, 2015 Share #216 Posted March 30, 2015 The 50 lux aspherical shows more of it than the 50 Apo Are you sure of that? Link to post Share on other sites More sharing options...
jankap Posted March 30, 2015 Share #217 Posted March 30, 2015 Here an example of the transmission of an exotic lens. This lens is designed to be very wide from UV, visual spectrum to IR and is made for industrial purposes. For a 60mm f/4 a list price of $5700 is very high. I added the red lines to show the visual spectrum. Also it is only part of a illustration. Even this lens is not flat in the visual part. Jan http://www.l-camera-forum.com/leica-forum/attachment.php?attachmentid=491369&stc=1&d=1427727270 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/242349-is-this-ca-problem-on-my-5014-asph-its-normal-or-not/?do=findComment&comment=2789833'>More sharing options...
pgk Posted March 30, 2015 Share #218 Posted March 30, 2015 Purple fringing - Wikipedia, the free encyclopedia Don't believe everything that you read on the web or wiki;)! Oldish, vague, and a web search will reveal just as many discussions as the one here. None are definitive as far as I can see. Link to post Share on other sites More sharing options...
Exodies Posted March 30, 2015 Share #219 Posted March 30, 2015 The lens does not produce blue spectrum by itself. Sunlight (all wavelengths) comes in, the visible part + IR and somewhat UV are refracted and lead to the sensor. The original question was: "Is this a CA problem on my 50/1.4 ASPH?". To answer the question "lens or sensor?" it would be interesting to see, what the lens does without the blue spectrum. Same picture with and without. Differential diagnostics so to say. The light coming from one "point" of the sharpness plane should come to one "point" of the sensor. Alas the lens tends to refract wavelengths differently. Achromatic, APO and nonAPO lenses are designed differently. But other than the design of audio amplifiers - flat from 10 Hz to 20.000 Hz - these lens types are optimized for 1, 2 or 3 wavelengths only (of course without peaking). And there is no band pass filter. So UV and IR can play for themselves. Jan If the purple is coming out of the sunlight and forming a fringe, then there should be somewhere in the image a purple deficient area. I haven't seen one. Or doesn't light work like arithmetic? (OT: I'm a big fan of wall photographs and the white wall in the other thread linked to above is stunning. Well done Denoir). Link to post Share on other sites More sharing options...
jankap Posted March 30, 2015 Share #220 Posted March 30, 2015 That is a good question! Cheshirecat, what do you think? Jan Link to post Share on other sites More sharing options...
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