DigiKam vs. LibRaw command Output Discrepancy

Question

Recently I have stumbled upon digiKam software which internally uses LibRaw library as a raw conversion engine.

I have tried to convert one of the images I have using digiKam with all conversion settings disabled/set to default (i.e. gamma 1.0, no auto brightness, camera WB, no exposure correction) and only I have an input a custom ICC profile and output color space set to AdobeRGB. The output looks like this:

However, when I do "almost" the same using LibRaw library from the command line (dcraw_emu.exe) which is compiled already with LCMS I get totally different results where colors are not as bright and shiny as they look in digiKam's output.

The parameters I used for LibRaw are (-4 -T -w -p custom.icc -o AdobeRGB.icc -o 0) which are supposed to match the default settings of digiKam.

Any idea why LibRaw command output looks kind of washed-out and has different colors?

Answer 1

The washed-out colors of LibRaw point to the output image being in linear color space without any gamma correction. Digikam obviously has gamma correction applied to the image. Note that most color spaces define a gamma correction function, which is usually close to gamma 2.2

This corresponds to how data are stored in a RAW file and the sensitivity of our eyes to distinguish colors at different luminance levels. If you want to read more on this matter, I suggest starting here: What is the purpose of gamma correction in today's screens and how does it relate to graphics and photography?

Answer 2

Because it is software for photographers, DigiKam’s developers probably feel their defaults produce a better results than a straight pass through. They want to provide photographers with sensible defaults. Digikam is opinionated in regards to photography.

Because it is software for developers, Libraw’s developers have a different intent. They want to give developers full control. The library is opinionated in regards to software development.