With respect to White Balance (WB) it appears as though Rawtherapee (RT) operates with what it calls the “Camera” method as the default choice for the initial setting of WB. According to Rawpedia that means the following:
Takes the white balance used by the camera. If you shoot only in raw (so no raw+JPG), put the white balance settings of your camera on auto. This should generally give good results.
When saying “result” it appears as though that means determining the initial values that get set for “Temperature”, “Tint”, and “Red/Blue equalizer”. I think temperature is measured using a unit referred to as “Kelvin” which corresponds to differing light conditions for the scene that is the subject of the photograph. A chart acquired from other sources suggests a range of light conditions as follows:
Color Temperature Light Source 1000-2000K Candlelight 2500-3500K Tungsten Bulb (household variety) 3000-4000K Sunrise/Sunset (clear sky) 4000-5000K Fluorescent Lamps 5000-5500K Electronic Flash 5000-6500K Daylight with Clear Sky (sun overhead) 6500-8000K Moderately Overcast Sky 9000-10000K Shade or Heavily Overcast Sky
In an example with which I am experimenting a raw file was obtained for a scene shot in normal outdoor sunlight. The initial value for Temperature ends is being set at 8969K (kelvin I think ?). If I change the “Method” to “AWB Auto” it gets changed to 9960K. These values are way different from what I’ve experienced in the past. I’m pretty sure the reason for that is because this raw file was produced by my new camera that creates such files in Canon .CR3 format. Apparently, RT Version 5.8 is unable to read the metadata from such files.
This creates a desire to know a little more about how these WB parameters are computed than what is explained in Rawpedia. As part of this experiment I did convert the raw file to Adobe Digital Negative (.dng) format. When I open the same camera shot with the raw file file converted to .dng format the Temperature ends up being 6119K with “Method” set as “Camera” and 6517K with “Method” set as “AWB Auto”. These are in the range I would expect.
Therefore, when it comes to metadata the question becomes “what metadata?” and “how is it used to determine these WB settings?”. In this case, the metadata element referred to as “White Balance” is set to “Auto” in both (cr3 and dng) files. An element referred to as “Color Temperature”, set to 5200, is present in the original camera produced (.cr3) raw file but NOT in the .dng format file.
Given that whatever value for “Temperature” is used to develop the raw file it DOES NOT get preserved in the form of metadata in the resulting image file (or any place else as far as I can figure) why does it matter what value was used? In that, how authentic are these temperature values even in the best case? Since it seems there is no absolute correct value is it possible that the huge discrepancy experienced here is NO more significant than the minor discrepancies normally experienced.
By the way, when Rawpedia says “If you shoot only in raw (so no raw+JPG), put the white balance settings of your camera on auto.”, what is the rationale behind that assertion?