Adam Bonn Posted March 28, 2021 Share #1 Posted March 28, 2021 Advertisement (gone after registration) Hi everyone, I was hoping to get some advice.. The Premise I'd like to create forwarding matrices for use with the 'embedded' profiles that Leica include with their cameras. My Problem I've read (and re-re-re-re-read!!) the adobe DNG spec document and I just can't get my head round what I need to do... I think I'm ok with the maths.... I'm lead to believe that the Forward Matrices (hereon in 'FM' for brevity) can be calculated using the data found in the Colour Matrices (CMs) The maths for this seems fairly simple.... From Adobe: First, invert the XYZtoCamera matrix. CameraToXYZ = Inverse (XYZtoCamera) Second, the white balanced transform is computed CameraToXYZ_D50 = CA * CameraToXYZ (CA is an equation found on Bruce Lindbloom's site) I'm using excel to perform the maths... (MINVERSE to inverse matrices and MMULT to multiple them) I'm not managing to get values that work (hell I'm not even managing to get values that look right!!) I'm fairly sure that the my problem is the data I'm using to base the XYZtoCamera inversion on (but don't take my work for it !!) Originally I thought that this was simply the CMs inversed, but I guess not.... I think I have to apply a matrix calculation to the CMs in order to obtain the correct values to invert I was hoping that someone here could help walk me through it.... There are a few blogs etc that detail this process, however they start from a base colour target and build a profile from scratch... what I want to do is piggyback from Leica's existing CMs Thanks in advance for any help Link to post Share on other sites More sharing options...
Advertisement Posted March 28, 2021 Posted March 28, 2021 Hi Adam Bonn, Take a look here Help with Creating DNG Spec Forwarding Matrix. I'm sure you'll find what you were looking for!
Jeff S Posted March 29, 2021 Share #2 Posted March 29, 2021 Maybe some of the information presented here might help... https://www.odelama.com/photo/Developing-a-RAW-Photo-by-hand/Developing-a-RAW-Photo-by-hand_Part-2/ Jeff 1 Link to post Share on other sites More sharing options...
Adam Bonn Posted March 30, 2021 Author Share #3 Posted March 30, 2021 Thanks Jeff I’ve looked at that site before and it is very informative, but it starts from the base of independent data collection Link to post Share on other sites More sharing options...
Adam Bonn Posted March 30, 2021 Author Share #4 Posted March 30, 2021 Perhaps I need to phrase my question differently using nothing more than the two CMs and the ‘as shot neutral’ tag value that Leica embed into the dng how do i created a single matrix using mired interpolation? I would like to do this in excel. I don’t have matlab. Anyone? Link to post Share on other sites More sharing options...
jaapv Posted March 30, 2021 Share #5 Posted March 30, 2021 I am wondering: what would be the advantage of this exercise over profling existing raw conversions? Link to post Share on other sites More sharing options...
Adam Bonn Posted March 30, 2021 Author Share #6 Posted March 30, 2021 I wish to add the 'missing' forward matrices to leica's embedded profiles Link to post Share on other sites More sharing options...
jaapv Posted March 30, 2021 Share #7 Posted March 30, 2021 Advertisement (gone after registration) I see. Would it not be far simpler to create colour profiles in your raw converter? Link to post Share on other sites More sharing options...
Adam Bonn Posted March 30, 2021 Author Share #8 Posted March 30, 2021 42 minutes ago, jaapv said: I see. Would it not be far simpler to create colour profiles in your raw converter? Yes (and I've done this in the past) But I want to learn how to do the thing that a member did to some degree of fanfare. See here Seems like we were both convinced! 2 Link to post Share on other sites More sharing options...
Adam Bonn Posted April 1, 2021 Author Share #9 Posted April 1, 2021 So @jaapv do you know how to do this? Link to post Share on other sites More sharing options...
jaapv Posted April 1, 2021 Share #10 Posted April 1, 2021 Prevent a yellowish cast under LED light? Set the camera colour balance by a greyscale reading off a white piece of paper in the relevant light. Then warm up the image to taste using the yellow-blue slider in the colour balance dialog. Otherwise, in Photoshop, change the contrast curve of the *B channel in LAB.. Link to post Share on other sites More sharing options...
Adam Bonn Posted April 1, 2021 Author Share #11 Posted April 1, 2021 4 hours ago, jaapv said: Prevent a yellowish cast under LED light? Set the camera colour balance by a greyscale reading off a white piece of paper in the relevant light. Then warm up the image to taste using the yellow-blue slider in the colour balance dialog. Otherwise, in Photoshop, change the contrast curve of the *B channel in LAB.. No not that Calculate the correction forwarding matrices from the embedded colour matrices using chromatic adaptation Link to post Share on other sites More sharing options...
jaapv Posted April 1, 2021 Share #12 Posted April 1, 2021 I wouldn't... Link to post Share on other sites More sharing options...
Adam Bonn Posted April 1, 2021 Author Share #13 Posted April 1, 2021 (edited) 30 minutes ago, jaapv said: I wouldn't... Wouldn’t or couldn’t? And if wouldn’t, why not? Edited April 1, 2021 by Adam Bonn Link to post Share on other sites More sharing options...
jaapv Posted April 1, 2021 Share #14 Posted April 1, 2021 Possibly couldn't too, mainly due to laziness in adding brain clutter, but wouldn't because I see no advantage over profiling and editing in a colour-managed workflow 1 Link to post Share on other sites More sharing options...
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