Difference between revisions of "Talk:Chromatic aberration"
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(Strange Example caused by IR?) |
Erik Krause (talk | contribs) |
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==Strange Example== | ==Strange Example== | ||
In the strange example on the page are we perhaps seeing chromatic aberration of longer wavelength red (approaching near IR)? Most plants reflect a lot of longwave red (as made obvious in IR photographs of plants)... this would explain why correction for the plant would cause more problems for red elsewhere in the image. I'd only expect to see this if the error of the lens was fairly steep with respect to wavelength, but that wouldn't be shocking if the lens was designed for a sensor (film?) with less NIR response. --[[User:Gmaxwell|Gmaxwell]] 05:33, 30 October 2006 (CET) | In the strange example on the page are we perhaps seeing chromatic aberration of longer wavelength red (approaching near IR)? Most plants reflect a lot of longwave red (as made obvious in IR photographs of plants)... this would explain why correction for the plant would cause more problems for red elsewhere in the image. I'd only expect to see this if the error of the lens was fairly steep with respect to wavelength, but that wouldn't be shocking if the lens was designed for a sensor (film?) with less NIR response. --[[User:Gmaxwell|Gmaxwell]] 05:33, 30 October 2006 (CET) | ||
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| + | == Great article on LCA/TCA == | ||
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| + | I found http://www.vsg.dcu.ie/papers/prl_2007_chrom.pdf an article to measure and correct LCA/TCA chromatic aberration. Based on a fundamental model it measures CA on a test image (chess board pattern) to calibrate a lens. [[User:Dedalus|Dedalus]] 22:59, 6 July 2008 (CEST) | ||
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| + | :The upcoming [[hugin]] package will contain a tool to automatically determine TCA correction parameters ([[tca_correct]]) to be used with [[fulla]] to correct TCA. Unfortunately I don't know enough about it to write something... <small>--[[User:Erik Krause|Erik Krause]] 21:54, 10 July 2008 (CEST)</small> | ||
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| + | ::As far as I know tca_correct only takes radial TCA into account, while the paper takes asymmetric distortion due to misalignment of lens elements into account as well (so called tangential distortion). [[User:Dedalus|Dedalus]] 12:54, 16 July 2008 (CEST) | ||
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| + | :::Almost all RAW converters offer linear CA correction (channel scaling) only and photographers apparently are happy with it. Using a polynomial model seems already esoteric to most, given the fact that it is almost impossible to determine and correct TCA in a normal bayer-interpolated digital camera image. As long as there is no good raw converter that offers a plugin interface for TCA correction it is quite academic to think about even more sophisticated models. <small>--[[User:Erik Krause|Erik Krause]] 22:58, 21 July 2008 (CEST)</small> | ||
Latest revision as of 22:58, 21 July 2008
Strange Example
In the strange example on the page are we perhaps seeing chromatic aberration of longer wavelength red (approaching near IR)? Most plants reflect a lot of longwave red (as made obvious in IR photographs of plants)... this would explain why correction for the plant would cause more problems for red elsewhere in the image. I'd only expect to see this if the error of the lens was fairly steep with respect to wavelength, but that wouldn't be shocking if the lens was designed for a sensor (film?) with less NIR response. --Gmaxwell 05:33, 30 October 2006 (CET)
Great article on LCA/TCA
I found http://www.vsg.dcu.ie/papers/prl_2007_chrom.pdf an article to measure and correct LCA/TCA chromatic aberration. Based on a fundamental model it measures CA on a test image (chess board pattern) to calibrate a lens. Dedalus 22:59, 6 July 2008 (CEST)
- The upcoming hugin package will contain a tool to automatically determine TCA correction parameters (tca_correct) to be used with fulla to correct TCA. Unfortunately I don't know enough about it to write something... --Erik Krause 21:54, 10 July 2008 (CEST)
- As far as I know tca_correct only takes radial TCA into account, while the paper takes asymmetric distortion due to misalignment of lens elements into account as well (so called tangential distortion). Dedalus 12:54, 16 July 2008 (CEST)
- Almost all RAW converters offer linear CA correction (channel scaling) only and photographers apparently are happy with it. Using a polynomial model seems already esoteric to most, given the fact that it is almost impossible to determine and correct TCA in a normal bayer-interpolated digital camera image. As long as there is no good raw converter that offers a plugin interface for TCA correction it is quite academic to think about even more sophisticated models. --Erik Krause 22:58, 21 July 2008 (CEST)