I recently did the profiling for a TZ-100 camera. I shot down a couple
of notes while doing it; I share them here hoping they can be of help...
I started with the information in the following sites:
- http://www.darktable.org/2012/12/profiling-sensor-and-photon-noise/
- https://landscrapes.wordpress.com/2016/05/10/darktable/
and tried to simplify the thing as much as possible.
First of all, you need the tools directory of the source version of your
darktable. I decided to clone the git repository and then checkout the
same stable version I have from the darktable PPA [link]. Basically, I
did the following (suppose you're in your home directory):
git clone https://github.com/darktable-org/darktable.git
cd darktable
git checkout release-2.2.4
git reset --hard
...and now the tools for noise profiling are in
`~/darktable/tools/noise`; let's calle this directory `NP`.
NP=~/darktable/tools/noise
Now it's time to take your photos. You need a series of photos, at all
ISO you want to have the profile, that must be
- unfocused
- have both overexposed and underexposed areas
- assigned the "raw linear" profile
...where the second one is the most difficult thing to achieve.
Especially for low ISO values.
Once you have the shots that have a lot of histogram data (see example
here) you can go applying the raw linear profile to them. You have to
use the right hand "styles" module of the lighttable and "import" the
file "raw linear.dtsyle" you will find in $NP; after that select all of
your raw files and apply iy. They will turn greenish - it's ok.
Now you go in the directory in which you have the photos and do the
following:
$NP/gen-profile -d .
If all is well, at the end you will have a `preset.json` file with your
noiseprofiles. You can test it by calling darktable with:
darktable --noiseprofiles presets.json
and trying to apply it to your photos.
Errors are quite common at this point. I had a couple of them:
1. `gen-profile` bails out saying that the image is not underexposed. I
have to re-shot it, with less exposure.
2. `gen-profile` bails out saying that some channel (I had just green)
is wrong. This normally means that the picture has no sufficient
overexposure.
On 05/07/17 13:29, Аl Воgnеr wrote:
I have uploaded new and hopefully better noise images from a Pentax KP
to
https://drive.google.com/drive/folders/0Bx7crlmGDudaaG11OURYN184ZzQ?usp=sharing
and now I want to follow
http://www.darktable.org/2012/12/profiling-sensor-and-photon-noise/
where I read, I should execute
~/darktable/tools/noise/gen-profile -d .
But my Ubuntu-system doesn't contain a file gen-profile, so I searched
for it and found
https://github.com/darktable-org/darktable/blob/master/tools/noise/gen-profile
Is it enough to download this script or do I need more?
Al
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Romano Giannetti
http://www.rgtti.com/
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