[darktable-devel] Dark frame removal and vignetting correction

[Novák Levente]

Hi,

Dark frame removal and vignetting correction are two rather important
features for low light (e.g. astro) photography. There was a request for
such functionalities more than one year ago. Is there any progress since
then?

Levente

[Torsten Bronger]

Hallöchen!

Post by Novák Levente
Dark frame removal and vignetting correction are two rather
important features for low light (e.g. astro) photography. There
was a request for such functionalities more than one year ago. Is
there any progress since then?

Do you mean http://darktable.org/redmine/issues/9038 with
"vignetting correction"? I toy with the idea of implementing 9038
in LensFun.

Tschö,
Torsten.

[Novák Levente]

Post by Torsten Bronger
Hallöchen!

Post by Novák Levente
Dark frame removal and vignetting correction are two rather
important features for low light (e.g. astro) photography. There
was a request for such functionalities more than one year ago. Is
there any progress since then?

Do you mean http://darktable.org/redmine/issues/9038 with
"vignetting correction"? I toy with the idea of implementing 9038
in LensFun.
Tschö,
Torsten.

Hi,

Yes, for the vignetting (flatfield) part. But there is also the dark
frame removal feature which removes thermal noise. This can not be done
in lensfun as it depends on the sensor chip not the lens. Also, even for
the vignetting part if someone uses a telescope without a regular photo
lens attached it does not really make sense to use lenfsun.

The best would be to a) allow a frame be subtracted from the shot (for
dark frame removal) and b) to multiply the luminosity values of the shot
at each pixel position by a factor calculated from the photo of an
evenly lit white surface (for flat field correction).

Can't the source code of RawTherapee be used for these? It does contain
these features.

Levente

[Torsten Bronger]

Hallöchen!

Post by Novák Levente

Post by Torsten Bronger
[...]
Do you mean http://darktable.org/redmine/issues/9038 with
"vignetting correction"? I toy with the idea of implementing
9038 in LensFun.
[...]

Yes, for the vignetting (flatfield) part. But there is also the
dark frame removal feature which removes thermal noise. This can
not be done in lensfun as it depends on the sensor chip not the
lens. Also, even for the vignetting part if someone uses a
telescope without a regular photo lens attached it does not really
make sense to use lenfsun.

I've pondered this thoroughly and came to the conclusion not to take
"Lens" in "LensFun" too literally. After all, even TCA and
vignetting correction depend on the sensor if you are pedantic.
Moreover, LensFun always has the information which sensor was used.
Currently, it only takes the cropfactor info out of it -- but why
not more. Besides, at least three of the things you correct with
flatfields (vignetting, coloured corners, sensor dust) heavily
depend on the lens model and settings.

The API has to be extended by just one field: the timestamp of the
picture.

I don't say that I do that, but only because I don't know whether I
will have the time and skills. I'm halfway through with flatfield
correction in a standalone Python program. This would be needed to
be translated to C++ then (which is not my primary language).

Post by Novák Levente
[...]
Can't the source code of RawTherapee be used for these? It does
contain these features.

I haven't looked at the code but I doubt this is worth the effort.
Typically, you have to change much when porting code from one
program to another, and the "core" of this feature is a simple
pixel-wise multiplication, possibly with an interpolation.

Tschö,
Torsten.