Washington Posted June 8, 2011 Share #81 Posted June 8, 2011 Advertisement (gone after registration) I can be silly at times about things I don’t understand and I surly can barely understand the intelligent postings of those who desire to get to the bottom of this. But, I really don’t know why different lenses of the same length will give very different results concerning red-edge? Quote Link to post Share on other sites More sharing options...
Advertisement Posted June 8, 2011 Posted June 8, 2011 Hi Washington, Take a look here Towards an explanation of the Italian Flag Phenomenon. I'm sure you'll find what you were looking for!
Double Negative Posted June 8, 2011 Share #82 Posted June 8, 2011 I can be silly at times about things I don’t understand and I surly can barely understandthe intelligent postings of those who desire to get to the bottom of this. But, I really don’t know why different lenses of the same length will give very different results concerning red-edge? Variations in lens tolerances for one. And even two shots from the exact same camera might not necessarily show the same effects due to environmental variables (e.g. light). Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted June 8, 2011 Share #83 Posted June 8, 2011 Variations in lens tolerances for one. And even two shots from the exact same camera might not necessarily show the same effects due to environmental variables (e.g. light). And in that case we're screwed. No generalised remedy is possible – except of course telecentric lenses for digital M cameras. Hooray. The old man from the Age of Doom and Gloom Quote Link to post Share on other sites More sharing options...
mjh Posted June 8, 2011 Share #84 Posted June 8, 2011 But, I really don’t know why different lenses of the same length will give very different results concerning red-edge? Fellow member ‘isaac’ has recently found a correlation between decentered lenses (specifically lenses with an optical axis that isn’t perpendicular to the sensor) and red edges. As to why (assuming this observation can be generalized), nobody really knows. But again, Leica thinks they know, so there’s still hope. Quote Link to post Share on other sites More sharing options...
otto.f Posted June 8, 2011 Share #85 Posted June 8, 2011 (edited) But, I really don’t know why different lenses of the same length will give very different results concerning red-edge? You mean same length AND speed? My Summaron 2.8/35 is coded as Summarit 2.5, if I would give in Summilux 1.4 when using the Summaron, the correction is not perfect. If you compare a Summilux 35 and a Summarit 35 in build, for instance on the Leica site under technical data of lenses, you see that the Summilux penetrates deeper into the body (no pun intended) than the Summarit, (and I'm sure you can even compare it live with two lenses of the same length and different speeds out of your own rich collection), so I'd say that this must result in different angles of incident. Maybe I'm silly too, but then only in this domain Edited June 8, 2011 by otto.f Quote Link to post Share on other sites More sharing options...
Lindolfi Posted June 8, 2011 Author Share #86 Posted June 8, 2011 (edited) Thanks again for the contributions. The variations in Italian Flag Phenomenon with the same camera and the same lens in different light conditions must be due to the differences in base colour over the image, so that sometimes it is less obvious. For instance the fact that hardly anyone mentions the reddish colour at the bottom of the image is due to the fact that most of the time no sky or clouds or evenly coloured surface is visible in average images of the world around us in the lower part of the image. To make it clear again: we are not trying to solve a problem that Leica should solve or is solving. As stated, we can just wait for a solution from Leica without thinking about it. But I'm just curious! Over time we have developed a great understanding of our tool, the M9, and it really creates a bond, this understanding, at least that is what I feel... If we want to study the phenomenon, it should be done without correction, so no coding. Else you study two things: the phenomenon and the attempt by the firmware to correct it. Another remark: if indeed the Italian Flag Phenomenon is due to a shift of microlenses relative to the pixel array, it must me very systematic, since (without correction) you always see the reddish colour left and bottom, rather than right and top. It would be very nice to do the standard test with evenly lit white and non-shiny opaque plastic in front of the lens with the same lens and different bodies to see just how variable it is across M9 camera's. Edited June 8, 2011 by Lindolfi Quote Link to post Share on other sites More sharing options...
Washington Posted June 8, 2011 Share #87 Posted June 8, 2011 Advertisement (gone after registration) Same speed? Well, almost. For instance, I use 3 21mm lenses: 1. A 21mm f4 C.V which I code at the 21mm f4 16-18-21 position. 2. A Konica Hexanon Dual 21-35mm which I also code as above but it is f3.4 lens on 21mm setting. 3. A Kobalux Super Wide 21mm f2.8 …. which I code at the 21/f2.8 setting. Of the three the Konica give the least red-edge if any with the Kobalux very very close. The CV some but not terrible and an easy fix in Corner-Fix. That’s all I know. Cheers. Quote Link to post Share on other sites More sharing options...
otto.f Posted June 8, 2011 Share #88 Posted June 8, 2011 That’s all I know. Cheers. You know more: the distance of the back lens to the sensor is different for these three lenses Quote Link to post Share on other sites More sharing options...
Washington Posted June 8, 2011 Share #89 Posted June 8, 2011 Gee, that’s probably so… I never took note of that. But, do you think THAT could have something to do with it? Maybe… something else to consider. Quote Link to post Share on other sites More sharing options...
otto.f Posted June 8, 2011 Share #90 Posted June 8, 2011 Yes I think so because it determines the angle of incidence on the sides of the sensor Quote Link to post Share on other sites More sharing options...
Double Negative Posted June 8, 2011 Share #91 Posted June 8, 2011 The amount that the lens protrudes into the camera has everything to do with which lens produces more (or less) red edge. The rays of light are at an increasingly oblique angle the further in the lens protrudes, which is the primary cause of red edge. For example, the 4,5/21 and 2,8/21 ZM lenses. The former is "unusable" whereas the latter can be corrected with a Leica code. Why? The former is physically shorter and protrudes more. It's not the speed of the lens so much - but stopping down. As you stop down, the effect should worsen as you're bending the light rays more. I haven't tested this theory however. Quote Link to post Share on other sites More sharing options...
Lindolfi Posted June 8, 2011 Author Share #92 Posted June 8, 2011 (edited) Yes I agree with the protrusion effect (the deeper, the stronger the effect on the Italian Flag Phenomenon), which has to do with the position of the back principle plane from which the rays start to spread to the sensor. Double Negative: it is the other way around: I measured the effect of the aperture and the Italian Flag Phenomenon is stronger when you open the aperture (see here) That also makes sense: when you open the aperture more contribution occurs from entering rays from the opposite border of the aperture, coming more oblique to the sensor. The effect however is small. Edited June 8, 2011 by Lindolfi Quote Link to post Share on other sites More sharing options...
otto.f Posted June 8, 2011 Share #93 Posted June 8, 2011 (edited) Yes following the Persian carpet-model (post #64) this is quite logical: imagine you hang above a Persian carpet at the centre, then the closer you come to the carpet, the more difference you will see between left and right in saturation and reflection. I read in this forum somewhere that the setting of the Elmarit 21 is better for the CV 15 than the WATE at 16mm, this is probably caused by the same phenomenon. So what would really matter is not the focal length in itself but the amount of protrusion into the body Edited June 8, 2011 by otto.f Quote Link to post Share on other sites More sharing options...
otto.f Posted June 8, 2011 Share #94 Posted June 8, 2011 (edited) It would be very nice to do the standard test with evenly lit white and non-shiny opaque plastic in front of the lens with the same lens and different bodies to see just how variable it is across M9 camera's. I am looking forward to such a test between colleagues/friends/hobbyists, because I believe that the IFP is not caused by production variations/failure in terms of displacement of the optic glass above the sensor. I'm inclined to believe that IFP is inherent in the design of the digital M, this is: in the construction of micro-lenses in front of the sensor as such, without which it was impossible to produce a digital M. No matter how perfect you align, IFP cannot be avoided from 35mm and shorter Edited June 8, 2011 by otto.f Quote Link to post Share on other sites More sharing options...
pop Posted June 8, 2011 Share #95 Posted June 8, 2011 All observations appear to support the hypothesis that the angle at which the light arrives at the sensor is responsible for the effect. What may make it hard to formulate a model of the root cause or causes might derive from the fact that all (known to me) observations are made with an image of a uniform white out-of-focus plane. Given the resolution of the lenses at hand, what would be the narrowest monochrome line that can be depicted on the sensor in terms of sensor pits? How narrow would be the sharpest edge between - say - a monochrome red and a black area? Quote Link to post Share on other sites More sharing options...
Olsen Posted June 8, 2011 Share #96 Posted June 8, 2011 Even if it is 'easy to fix' with some sort of post processing, my opinion is that 'The Italian Flag' is an issue. Had I known about the problem, I would not have bought my M9. But rather kept on using my M8. What is the conclusion of all this? Is it possible for Leica to fix it by a software update? Or do we have to wait until a future M10? Quote Link to post Share on other sites More sharing options...
Lindolfi Posted June 8, 2011 Author Share #97 Posted June 8, 2011 Pop, The best lenses have a resolution of well over 100 linepairs/mm, which should make it possible to have a change from light to dark over a distance of 5 micron. That is about the size of a pixel in the image and a site on the matrix of colour sensitive elements in the sensor. Quote Link to post Share on other sites More sharing options...
jaapv Posted June 8, 2011 Share #98 Posted June 8, 2011 Even if it is 'easy to fix' with some sort of post processing, my opinion is that 'The Italian Flag' is an issue. Had I known about the problem, I would not have bought my M9. But rather kept on using my M8. What is the conclusion of all this? Is it possible for Leica to fix it by a software update? Or do we have to wait until a future M10? The problem has been reported on the M8 as well.... Quote Link to post Share on other sites More sharing options...
Lindolfi Posted June 8, 2011 Author Share #99 Posted June 8, 2011 ...because I believe that the IFP is not caused by production variations/failure in terms of displacement of the optic glass above the sensor. I don't either, but between the cover glass and the matrix of colour sensitve sites, we have the microlenses... And with my diagram it is possible to explain the Italian Flag Phenomenon with a shift of these microlenses (given their chromatic aberration) along the diagonal of only a fraction of a pixel. 1 Quote Link to post Share on other sites More sharing options...
pop Posted June 8, 2011 Share #100 Posted June 8, 2011 Lindolfi - thanks for your very specific answer. Now, it's quite beyond my capabilities and beyond my equipment as well. But wouldn't we gain more insights into the nature of the effect if we could study - say - one sharp monochrome edge close to an edge of the sensor? Spillover into pits of different colours or multiple recordings of the same edge would possibly become apparent (or not become apparent, depending on the nature of the phenomenon). The rationale behind the suggestion is, of course, to avoid the averaging effect of depicting a featureless white blob. Quote Link to post Share on other sites More sharing options...
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