> 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
>>
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> Lensfun-users@lists.sourceforge.net
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