> Not sure if it helps, but the parameters for the 3 planes are so similar > so that I simply would take the mean values of each parameter and go with > it. >
I agree that this is definitely the place to start. The vendor of the lens also had to fit the model to the lens - the > deviations in each of the 3 planes are compatible with typical small > fitting errors. Parameters are equal to the 3rd or 4th significant digit > which is very precise. > You may well be right, but remember that the full width of the image is 1.0, while a chromatic aberration is typically on the order of 1-2px, so I would expect to find very similar values here. For example, the first random lens that I've looked up in the lensfun db has tca parameters around 10^-4. Thanks, Graeme > On 21 Nov 2021, at 19:18, Graeme Leese <gnl...@gmail.com> wrote: > > > Hi, > > I know basically nothing about DNG, but Googling suggests that yes, the > planes are probably referring the different color channels. There's a tag > CFAPlaneColor that sets which order the colors map to the planes or else > they're RGB. > > Chromatic aberration is essentially when the different colours are > distorted differently, so my first guess is that you should calculate the > distortion from the average of the planes. Then the difference between the > planes should be encoded in the TCA parameters. Alternatively, since the > TCA parameters are given for R and B, perhaps it would work better to take > the distortion only from the G plane, I'm not sure. > > I haven't tried to work out how the TCA parameters would be derived. If > the method looks like it's working then I can probably have a look and see > if the calculation is simple enough, or else it should be simple enough to > write a script to find the values that match the warp from the dng file. > > I don't think lensfun encodes the optical centre from the warp (so it > would have to be set to 0.5, 0.5). I'm not sure how much that would affect > the accuracy of the data. It's also worth noting that the DNG file uses > different coordinates for pixels (0,0 in the corner) than lensfun (0,0 in > the centre). > > Hope that helps. I'm interested to know how you get on with converting the > information. > > Thanks, > Graeme > > > > On Wed, 17 Nov 2021, 13:05 Gunar Kachel, <gunar.kac...@gmail.com> wrote: > >> Hi, my lens is not yet supported by lensfun. I therefore searched for a >> method to to get the right distortion and chromatic aberration profile to >> be used in daktable. (And I was not very successful applying the "manual" >> method using Hugin.) >> >> However, as this is a modern lens the profiles are already integrated in >> the RAW file and I therefore followed this procedure: >> >> 1. convert the RAW file (NEF) to DNG using Adobe DNG Converter >> 2. extract OpCoodeList3 parameters from DNG file using >> dng-validate.exe (at the bottom) >> >> >> I assume I can implement these values using the lensfun distortion >> profile model "acm". >> However I'm puzzled that values are provided in several "planes". >> Are the planes referring to different color channels? >> How to implement the planes in lensfun? >> How can I cover chromatic aberration using these information? >> >> Thanks in advance for the insight! >> >> Sample output from dng-validate.exe -v: >> >>>>>>>>>>>>>>>> >> Opcode: WarpRectilinear, minVersion = 1.3.0.0, flags = 0 >> Planes: 3 >> Optical center: >> h = 0.501405 >> v = 0.504913 >> Plane 0: >> Radial params: 1.025498, -0.124349, 0.058447, -0.003755 >> Tangential params: 0.000000, 0.000000 >> Plane 1: >> Radial params: 1.025181, -0.124368, 0.058438, -0.003759 >> Tangential params: 0.000000, 0.000000 >> Plane 2: >> Radial params: 1.025277, -0.124355, 0.058413, -0.003751 >> Tangential params: 0.000000, 0.000000 >> <<<<<<<<<<<<<<<<< >> _______________________________________________ >> Lensfun-users mailing list >> Lensfun-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/lensfun-users >> > _______________________________________________ > Lensfun-users mailing list > Lensfun-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lensfun-users > >
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