Hopefully, WB would not be peformed and the raw channels are merely displayed. As long as no channel clipping takes place, one can white balance using multipliers less than 1.0 if needed to prevent clipping.
Sounds cumbersome. Why not just set the correct WB while shooting? Or at least a preset that comes close (tungsten, daylight etc.). This way the histogram is "WYSIWYG" (so to speak).
I can understand that it may be annoying for you that your camera doesn't show a useful histogram and that your RAW software doesn't show the same histogram as your camera. But these limitations do not apply to all systems... obviously.
My camera (Nikon D3) does show a reasonable histogram and this histogram is very similar to that of ACR when one uses the necessary BaselineExposure correction of -0.5 in ACR. However, at times is is useful to look at the raw data without white balance. A good example is this yellow flower: the histogram with an ETTR exposure is shown in the ACR preview, when rendering into Adobe RGB, which was the space set in the camera and used for the JPEG preview and histograms. The histograms of the file as rendered into Photoshop by ACR are also show. The luminance histogram looks fine, but is heavily weighted towards the green so that the red and blue channels have little effect. The green in the RGB histogram is fine, but the red is clipped. Yellow, of course, contains red and green.
Camera histogram:
ACR histogram with Exposure -0.5 baseline correction:
Photoshop luminosity histogram:
PhotoshopRGB composite histogram:
Rawnalize histogram showing the raw data without any white balance:
Examination of the raw file in Rawnalize shows that the green and red channels are short of clipping. However, the WB multiplier for the green channel is 1.0 and that for the red channel is 1.7 as shown by Rawnalize. When white balance is applied, the red channel will be clipped, whereas it is intact in the raw file. One could decrease exposure in the camera so that the red is not clipped during normal white balance with a red multiplier of 1.7. However, a better approach is to use multipliers all less than one so that no white balance clipping can occur and one can get a better signal:noise. One can do this directly in DCRAW, but in ACR one would decrease the exposure.
To obtain a better evaluation of the RGB channels in the raw file, many Nikon users load a special White Balance into the camera, so that white multipliers of 1 are used for all channels (UniWB). A related ploy regarding WB is to place a magenta filter over the camera lens to hold back some of the green light and obtain a better balance between the channels. This can easily add a half stop to the DR. With older cameras with a limited DR, this was advantageous, but it is probably not worthwhile with current state of the art cameras.
Regards,
Bill
P.S.
In the example shown, it was not possible to eliminate red clipping by any reasonable decrease in exposure, becuase saturation clipping was occuring during rendering into the relatively narrow Adobe RGB space, which is the widest space available on this camera. One could eliminate such clipping through the use of ProPhoRGB.