The White Balance (WB) tool on the Color tab seems to always open with the Method set to “Camera”. I’m having a hard time figuring out what that means. Intuitively, it suggests that the temperature value which is displayed came from the camera. Rawpedia only says this “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.”. I sure don’t see how it comes from the camera. When I open a raw file for the first time (i.e., no pre-existing processing profile) the values that I’m seeing do not appear anywhere in the metadata of the raw file. For my camera that metadata does include parameters with names such as “ColorTempAsShot”, “ColorTempAuto”, and “ColorTempMeasured” but none are set to the value shown on the RT WB tool. Is it possible that the value is the result of some kind of analysis by RT of the raw data? For some reason that is what I’m thinking is meant by the Method called “Auto”.
Unlike some other digital editing programs, the WB tool is active when processing previously developed images (i.e., jpg or tif file rather than raw file). Interestingly when such an image has been developed by a camera it seems that there must be an actual value set for the WB temperature (i.e, by the camera) but as far as I can tell there is no way to determine, after the fact, what value was used (i.e., such is not part of the metadata). In actual practice it seems that RT always sets the initial value for the WB temperature to 6490 when opening a previously developed image for the first time. How could that be from the camera? Then let’s say the WB temperature is altered (e.g., 7500) and a new image is produced (i.e., saved). Then when that image is subsequently opened by RT the value for the WB temperature (i.e., Method defaulting to Camera) is again 6490.
It seems to me that no matter what is going on here it is a bit of a misnomer to refer to that WB method as “Camera”. However, no matter what the method is called is it possible to learn what is going on here? In that, where does that value come from both for raw and previously developed images. It would also be nice to see the actual multipliers, which as yet I’ve been unable to find.
As best I can tell those are metadata parameters for DNG files. My cameras happen to be Canon which uses files with an extension of CR2 and metadata as I described. Is it possible this amounts to a suggestion to convert CR2 to DNG?
hi, going from memory (I’d have to double check in the code, so take this with a fistful of salt), “camera” means that RT gets the channel multipliers from the raw metadata, and then converts them to a temp/tint internally. the resulting values depend also on the transformation matrix from camera to working space AFAIK, but the effect on the picture does not, because it always corresponds to the multipliers found. where such multipliers are, in turn, depends on the raw file being processed: I think each brand stores them in different places in the makernotes. I agree it would be nice to see the actual multipliers in the GUI (you can see them in the console in verbose mode).
for non-raw files, “camera” means do not scale the channels at all, and the temp/tint values you see are essentially fictitious. if you turn off the wb tool in this case, you should see no difference in output.
OK, that at least explains the behavior I’m seeing. While the temperature that RT displays is not what shows up using ExifTool it is fairly close. Using the raw data certainly makes sense but I had no idea that this kind of data might be included in the raw data. That clearly raises the question as to why the camera produced Exif data differs from what is in the raw file. It’s my understanding that WB is an essential part of the development process. In that, WB is applied to raw data. The raw data is what it is irrespective of WB settings. When the camera develops a jpg it must determine what WB setting is to be used. I would have thought that is what the RT Camera method referred to as well as what some element contained in the Exif data means. If Canon puts a different value in the raw data than in the Exif data, I an see that there is nothing RT can do about that.
When it comes to developed picture files (i.e., WB already applied) many photographers with more experience than I have would argue that the WB tool ought to be disabled. I must admit my use of it, to date, is not to accurately match the scene lighting but rather to obtain special (?artistic) affects that are desired. Those who know more about digital editing than me can probably obtain the same affects using other tools and I need to learn how to do that.
It looks like it should be fairly easy to experiment with conversion to DNG if for no other reason than to observe that metadata. I’ll give it a try.
Yes, that’s exactly what happens. The camera stores the multipliers for the various channels, and the RT “Camera” method uses those. They are converted into a temp/tint pair whose meaning depends on the specific algorithm used to perform this conversion, and that’s why you can see different temp/tint values for the same “Camera WB” when using different raw converters. But they will all correspond to the same multipliers (I suppose at least, as I don’t know what other closed-source tools actually do…)
@agriggio isn’t it also the case that the white balance temperature and tint values depend on the color matrix, and the color matrix used by the camera is unknown unless the camera shoots straight to DNG, therefore raw converters use color matrix values obtained after processing the proprietary raw files through Adobe DNG Converter, and so the final temp and tint in third-party software differs from that shown by the camera due to a difference between the matrices?
@Morgan_Hardwood absolutely. I mentioned this briefly in my first reply, but in the 2nd one I just abstracted it as “using different algorithms”
but it’s better to say so explicitly, I agree
I think you might be saying that what allows RT to process lots of different proprietary raw (i.e., different camera makers) files is that it uses Adobe DNG converter. Is that correct?
