On Fri, Jan 18, 2013 at 1:06 AM, Nico Wöhrle <[email protected]> wrote:
> Thanks for the answers.
>
> @ Tobias: the images look noisy in every zoom level, also in 100%.
>
> What I don't get about the "it is the image viewer" thing. My camera
> produced a RAW and a JPG file. The JPG processed from the RAW file (with
> darktable) looks by orders of magnitude noisier than the JPG which came
> directly from the camera. I don't understand why the gnome image viewer is
> able to show a normal JPG "correctly", but not a JPG coming from darktable.

I have a feeling you are confusing two unrelated issues.

a. Different programs resample images using different algorithms,
which may enhance sharpness (and increase apparent noise) or decrease
sharpness (and decrease apparent noise).

b. Also Darktable does not denoise your RAW files by default. And thus
is noisier than your camera generated files. Also completely expected.

RAW files are not simple uncompressed files. It's a raw sensor
capture, which requires a boatload of processing to even get a half
decent image. Some of the things camera's do are
1. Demosaicing
2. Curves
3. Color processing
4. Image dependent analysis and correction (Nikon Active D-light/Canon
Auto Lighting Optimizer/... on newer models).
5. Denoising
6. Sharpening

Most things about processing RAW files are camera specific and
completely undocumented/proprietary.

The particular problem with denoising is that everybody has different
preferences, and more importantly it's very CPU intensive
(particularly noticeable on older computers), so it's not enabled by
default.

Our website lists some of my screencasts on Darktable usage in
general, and it even has a screencast specifically about denoising
(using the nlmeans plugin):

http://www.darktable.org/resources/#screencasts

Regards,
Pascal de Bruijn

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