My Sony a7 has removed the hot mirror / internal color correction filter for use in infrared and ultraviolet photography. When shooting in UV, a special filter stack is used in order to only let UV through. For this reason, I make a custom white balance in the camera before shooting. Unfortunately, it is discarded by RawTherapee.
When viewing the image from the raw file on the screen of the camera as well as in Sony’s own image viewer, I do see the manually set white balance, and even in the thumbnails in RawTherapee (RT), I see the set white balance (WB) before opening the image. However, when opening the image, the white balance is “suddenly” wildly off. It looks extremely warm or magenta, even when the image doesn’t have much color differentiation (almost monochrome). Naturally, I can set the WB myself in RT, but it is a bit annoying that I don’t see the white balance I set manually in the camera before exposure. EDIT: I now see that the uploaded sample is not possible to fully correct in RT using the WB pipette because it isn’t possible to subtract enough magenta: The green/magenta scale is too limited. However, with another filter stack (the last image), it is possible to create a WB in RT.
In other words, the camera white balance is apparently discarded or not read by RT. I hope this can be fixed in a future update of RawTherapee.
I should add that the same issue applies to Adobe Camera Raw and DxO Photolab, but these raw converters have a minimum color temperature of 2000 Kelvin, which makes these raw converters unable to create a proper WB. Hence the need for a raw converter with a wider color temperature like RT. RT can go as low as 1500K, which is more than enough to reach a proper WB. Still, the camera WB is not used or shown when opening the image in RT.
That is correct, I think. The problem is when the raw converter doesn’t “accept” it because of its limitations in either tint (green/magenta) or temperature (blue/yellow) adjustment strength, as far as I can gather.
Well, the raw converter is not using that WB setting, as the raw converter does not necessarily want to recreate the OOC jpeg. That is why I shoot in raw format and try to develop my own jpeg the way I like it.
And btw, as long as RT did not open the raw, you see the embedded jpeg as a thumbnail. As soon as it was opened once a pp3 file is saved according your settings and so the final jpeg will be used as a thumbnail. Well may be not exactly as I described it … but I believe almost …
I believe that, in terms of UV, IR or full spectrum, the term “white balance” is a misnomer which can lead to confusion.
Be that as it may and pardon the Foveon mention, I found that raw IR files opened in the Sigma converter had lots of magenta with bottomed greens no matter what WB or colour adjustment was used - whereas those same raws opened in RawDigger had reasonably “recoverable” RGB rendition i.e. faux color detail using a separate editor.
No. Or rather, when doing that, the WB is way, way off. Extremely magenta or warm instead of spot on neutral like seen in camera or Viewer (Sony software).
Here I am referring to a manually set white balance (using a white subject in the actual light, with the actual filtering) in the camera, because there may not be a neutral/white object in the frame. For casual or ordinary photographs this may not be an issue, but for UV photography it is.
In addition, it isn’t possible to set neutral in RT at all with some filters because the extreme values aren’t extreme enough.
A pity the forum design doesn’t make it more clear who one replies to. That is standard in other places. However, if you look more closely, there is a visual indication (in this case the avatar image) who the reply is to.
