FlashGordonPhotography Posted March 22, 2015 Share #101 Posted March 22, 2015 Advertisement (gone after registration) Would have been interesting to compare them to my ones below. 50/1.4 asph, f/5.6, 1/500s & 1/60s, no fringing correction. Sure but this image has essentially none of the factors that allows purple fringing to rear it's very ugly head. The lens is stopped down, it's not back lit, the in focus point it lighter in tone than the background and the contrast isn't particularly high. You need almost the opposite of this shot to show fringing. Gordon Link to post Share on other sites More sharing options...
Advertisement Posted March 22, 2015 Posted March 22, 2015 Hi FlashGordonPhotography, 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!
lct Posted March 22, 2015 Share #102 Posted March 22, 2015 I was just comparing with Wilson's images above which are very similar i believe. Link to post Share on other sites More sharing options...
pgk Posted March 22, 2015 Share #103 Posted March 22, 2015 I explain that by more high-frequency light being reflected by these areas. ?????. Ahhhh yes, the wall..... There's no point continuing this discussion. Link to post Share on other sites More sharing options...
jaapv Posted March 22, 2015 Share #104 Posted March 22, 2015 Still, nobody has explained yet how it can be that the better a lens is corrected, the more purple fringing the image will show. Amongst the worst offenders are the Summilux 50 asph and Apo Summicron 90 asph. Link to post Share on other sites More sharing options...
lct Posted March 22, 2015 Share #105 Posted March 22, 2015 You need almost the opposite of this shot to show fringing. That's what i wanted to say to Wilson but i did not dare . Suffice it to shoot contre-jours at full aperture to get purple fringing and this works pretty well with all lenses including apos. Here 50/2 apo, f/2, 1/4000s & 1/500s. 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=2784938'>More sharing options...
wlaidlaw Posted March 22, 2015 Share #106 Posted March 22, 2015 The problem is that with an 18 SEM you have to be very close to the tree to get the branches big enough on the crop so they are not pixelated. The shot of this same tree on which I got the fringing with the 50 ASPH Summilux was indeed shot from the other side with the 18SEM. I just could not get physically close enough to the tree to shoot contre-jour and hoped that the blue sky might be bright enough to produce fringing but maybe it was not. As you show, maybe a bright grey sky might produce more of an effect. The first two shots were taken wide open at f3.4. I only did the third shot to try and see if the additional contrast of stopping down had a significant effect, which on the 18SEM it did not. I am not convinced that anything you do will produce much fringing on the 18SEM. Wilson Link to post Share on other sites More sharing options...
jankap Posted March 22, 2015 Share #107 Posted March 22, 2015 Advertisement (gone after registration) Ict, it is not necessary to load an overexposed picture. If I overexpose the correct exposed one in Photoshop I get the same result (more or less). It is a linear process, so by making the exposure extreme, one sees more. The effect is always present. More interesting would be to make the same picture with and without an UV filter. Then the in the lens not corrected spectrum should be filtered out. I don´t use filters, only polas. With polafilters one changes too much to compare results, I think. Jan PS What would happen, if one uses a yellow filter? The lens does not change the color of the light. Then sensor leaking could show its effect. Link to post Share on other sites More sharing options...
lct Posted March 22, 2015 Share #108 Posted March 22, 2015 Ict, it is not necessary to load an overexposed picture. If I overexpose the correct exposed one in Photoshop I get the same result (more or less). My first pic was overexposed actually. I should have shot it at f/2.8 or f/4 to get a correct exposure and no purple fringing would have been visible then most probably. Link to post Share on other sites More sharing options...
CheshireCat Posted March 22, 2015 Share #109 Posted March 22, 2015 ?????. Ahhhh yes, the wall.....There's no point continuing this discussion. What you see "on the wall" is actually an overlay of a high-frequency shape that is adjacent to the wall, magnified by CA. But before you leave the discussion, let us have some fun and explain this in terms of digital sensor issues. Because you can, right ? Link to post Share on other sites More sharing options...
CheshireCat Posted March 22, 2015 Share #110 Posted March 22, 2015 Ict, it is not necessary to load an overexposed picture. If I overexpose the correct exposed one in Photoshop I get the same result (more or less). Of course, as PF is not caused by sensor blooming. More interesting would be to make the same picture with and without an UV filter. Then the in the lens not corrected spectrum should be filtered out. I expect the filter to reduce the UV part that is not filtered by the sensor. An interesting test. But the problem here is that some high-frequency part of the visible spectrum may still be causing CA, as APO lenses are great but not perfect, especially outside of the plane of focus (and the branches here are in front of the plane of focus). What would happen, if one uses a yellow filter? The lens does not change the color of the light. Then sensor leaking could show its effect. Again and again: since you see the problem also overexposing later in photoshop it cannot be the sensor leaking (i.e. blooming). Besides, a yellow filter could not be perfect and still let some high-frequencies through. It is a nice experiment though. Link to post Share on other sites More sharing options...
CheshireCat Posted March 22, 2015 Share #111 Posted March 22, 2015 That's what i wanted to say to Wilson but i did not dare . Suffice it to shoot contre-jours at full aperture to get purple fringing and this works pretty well with all lenses including apos. Here 50/2 apo, f/2, 1/4000s & 1/500s. Thanks lct, you finally made it, and with an APO lens ! Note that the correction graph you see for APO lenses is in the plane of focus. APO performance outside the plane of focus is not the same. Now, could you please take another shot with the 50 APO focusing slightly in front of the tree, so we should be able to see greenish (or cyan) aberrations like in the very lower-left corner of your last image (I am pretty much sure that is a branch that was behind the focus field). P.S. The last shot you posted could already show this in other parts of the image (behind the focus field). If so, please post another crop. Link to post Share on other sites More sharing options...
lct Posted March 22, 2015 Share #112 Posted March 22, 2015 Did not keep those masterworks sorry. Here are two OOC jpegs shot at f/2, 1/4000s & 1/500s as well. Please fee free to tweak them as you like if need be. http://lctphot.smugmug.com/photos/3945597876_Ds8tQ8d-D.jpg http://lctphot.smugmug.com/photos/3945600135_kFtHggr-D.jpg (8MB files) Link to post Share on other sites More sharing options...
FlashGordonPhotography Posted March 22, 2015 Share #113 Posted March 22, 2015 Ict, it is not necessary to load an overexposed picture. If I overexpose the correct exposed one in Photoshop I get the same result (more or less). It is a linear process, so by making the exposure extreme, one sees more. The effect is always present. More interesting would be to make the same picture with and without an UV filter. Then the in the lens not corrected spectrum should be filtered out. I don´t use filters, only polas. With polafilters one changes too much to compare results, I think. Jan PS What would happen, if one uses a yellow filter? The lens does not change the color of the light. Then sensor leaking could show its effect. I use UVIR filters on all my lenses. Alas, they still show exactly the same purple fringe with one or without. Purple fringing happens at the sensor not in the lens. No lens faster than f2, that I have owned, has been completely free of PF. Does anyone have a lens that's f2 or faster and never gets PF? Gordon Link to post Share on other sites More sharing options...
lct Posted March 23, 2015 Share #114 Posted March 23, 2015 Got it with all my lenses more or less, even at f/4. According to Cambridge university, blooming is "a unique phenomenon of digital sensors that causes spillover highlight clipping — producing highly varied sensor-level color fringing that usually appears blue or purplish. It's most prevalent with sharp, clipped specular highlights on high resolution compact cameras. The classic example is the edges of tree tops and foliage against a bright white sky.". Link to post Share on other sites More sharing options...
wlaidlaw Posted March 23, 2015 Share #115 Posted March 23, 2015 Got it with all my lenses more or less, even at f/4. According to Cambridge university, blooming is "a unique phenomenon of digital sensors that causes spillover highlight clipping — producing highly varied sensor-level color fringing that usually appears blue or purplish. It's most prevalent with sharp, clipped specular highlights on high resolution compact cameras. The classic example is the edges of tree tops and foliage against a bright white sky.". I hope Olaf does not see you quoting "Cambridge in Colour" as a source of knowledge. He thinks they are like Manuel in Faulty Towers "they know nothing" :) I actually think their technical articles are rather good. Wilson Link to post Share on other sites More sharing options...
lct Posted March 23, 2015 Share #116 Posted March 23, 2015 As long as they match my experience they are good enough for me. Link to post Share on other sites More sharing options...
CheshireCat Posted March 23, 2015 Share #117 Posted March 23, 2015 As long as they match my experience they are good enough for me. That BS does not match your experience, unless you believe that stopping down the lens magically "fixes the sensor" instead of reducing the lens LoCA Link to post Share on other sites More sharing options...
Luke_Miller Posted March 23, 2015 Share #118 Posted March 23, 2015 That BS does not match your experience, unless you believe that stopping down the lens magically "fixes the sensor" instead of reducing the lens LoCA Perhaps a bit of both. Stopping down certainly reduces the amount of light striking the sensor, and typically improves lens performance. Link to post Share on other sites More sharing options...
lct Posted March 23, 2015 Share #119 Posted March 23, 2015 That BS does not match your experience, unless you believe that stopping down the lens magically "fixes the sensor" instead of reducing the lens LoCA "BS"?... It's not worth losing your temper for so little... Stopping down reduces the amount of light hitting the sensor such as highlights cause less clipping i guess but i'm no techie at all so i may be wrong. Link to post Share on other sites More sharing options...
CheshireCat Posted March 23, 2015 Share #120 Posted March 23, 2015 I use UVIR filters on all my lenses. Alas, they still show exactly the same purple fringe with one or without. Purple fringing happens at the sensor not in the lens. UV filters come in different strenghts. In any case, filters will not remove the visible light component of the PF. By the way, I just remembered my used Noctilux 50/1 came with a Leica UVa filter (13381). Does anyone know the specs of this filter ? No lens faster than f2, that I have owned, has been completely free of PF. Does anyone have a lens that's f2 or faster and never gets PF? I have never noticed PF with the Zeiss 135/2 APO Sonnar. However, I have never tried to provoke it. I will try, and keep you posted. Link to post Share on other sites More sharing options...
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