When comparing Raw and JPG images, there is little if any camera influence on raw files (other than exposure values of shutter speed, aperture and ISO of course). The camera settings are not in raw images, however the raw software provides its own similar settings (after we can see the image first to know what it needs).
There is another similar example about flash color, but 100K difference at lower WB temperature differences shows much more than 100K at higher WB temperatures.
These pictures are all the same simple quick setup with a D300. The light is the overhead incandescent ceiling light. White craft paper background, and a White Balance card behind cup.
First two are camera JPG, with camera Auto WB and then Incandescent WB.
Next two are raw, with camera Auto WB and then Incandescent WB, but AS SHOT in Adobe Camera Raw.
Then raw processed with Adobe Tungsten, then with WB tool on the white card, and Adobe Auto WB.
Some users seem not to see color differences, but correcting color can be pretty easy.
Pictures ae shown individually below, with default settings, except as noted.
JPG from camera, camera WB Auto, Adobe WB As Shot.
"As Shot" is the Adobe default WB when opening a new file first time, but the default can be changed.
As Shot, Auto, and Custom are the only WB choices for JPG (JPG already has camera settings in it). My notion is that As Shot adds nothing for JPG - shows it as it is, like any other editor.
JPG from camera, camera WB Incandescent, Adobe WB As Shot.
The subject was white, the light was incandescent, but this is rather blue (there are many types of incandescent bulbs). In the histogram of this white subject (with a white peak), you can see blue is higher than red there. In the first Auto picture, red is higher than blue.
The effect of the white balance temperature is to shift the red and blue channels back and forth in opposite directions (blue is high at low K temperature, red is high at high K temperature... to correct them). Tint sort of shifts both red and blue (magenta) with respect to green. Tint and Temperature are the Lab color a and b axes. And metered white subjects routinely need to be compensated to be a bit brighter too. I did + 2/3 EV here, but it needed more (not corrected here).
We can also process JPG in Adobe Raw, often with advantage - better tools and lossless edits for example. Lossless edits do require that we adapt to a little different philosophy (we have to output a new JPG file for other programs to see edits). Of course, if intending to do this, shooting in raw in the first place offers more advantage, but for example, little compact camera JPG images are easily processed this way too.
Raw from camera, camera WB Auto, Adobe WB As Shot. 4150K Tint -2.
Now some would superficially say, "See? Adobe Raw duplicates the camera JPG images". Both are sort of brown, and As Shot WB is the initial ACR default, but of course, not really, there are quite a few more details, next below.
Raw from camera, camera WB Incandescent, Adobe WB As Shot. 2900K Tint -2.
These two Raw As Shot images superficially look pretty close to the JPG, but note the incandescent histograms are rather different, and the picker color values are not the same, showing more range of difference now (a color picker spot is placed just above the cup, same spot in all images here, and its RGB color values show just above the image). You might think there was some mistake made (I did at first), since the tall blue spike at zero looks like the Auto histograms, but note that red and blue are reversed from Auto, same order and still blue like the camera Incandescent As Shot. So it is an Incandescent WB, and looks similar, but not at all the same result. FWIW, holding ALT key and clicking Blacks, that shifting blue near low end of the histogram is all the yellow flower (dim blue component vs zero blue, and a bit brighter overall).
JPG images do of course have camera white balance applied in the data. Raw files do not contain any white balance information (raw is of course raw, no camera settings at all), but Adobe As Shot WB does try to interpret and apply WB from the Exif data (applied in the output RGB image the raw editor is showing us now). Temperature degrees K is not in the Exif, but there is a RGB matrix multiplier value.
But for example,
Is any of this a problem? Of course not, one big point of raw is to be able to ignore all of the camera stuff, and instead to actually see the image before we have to decide how to fix it. We have better tools, camera oriented tools, and we simply make the settings in raw instead of in the camera, whatever pleases us, with live view of the results, leisurely, later at home. That's a very big deal.
It is said that Nikon raw software tries to extract several more settings from the Exif, but Adobe only tries to decipher White Balance. Nikon has previously considered our Exif data to be their private property (they even tried encrypting Exif white balance in the D2X/D2H about ten years ago).
Saying, Adobe As Shot WB does not match the camera JPG all that closely. But better, for raw, WB in the camera becomes unimportant, simply does not matter, because for one, camera WB is surely somewhat wrong anyway, and two, the purpose and advantage of raw is that we can see it first, and can simply correct it as we desire it to be, where we can see and know what we are doing. Raw offers good, easy, fast tools.
Same raw image, camera WB Incandescent, selecting Adobe WB Tungsten. 2850K Tint 0.
(two words with the same meaning here, incandescent light bulbs have tungsten filaments).
For raw images, we now have the standard WB menu, same as is in the camera, and we can simply select Daylight or Cloudy or whatever, even Auto, same as we do in the camera. The idea of raw is to defer it until here, when we can see it, and have great tools, and can judge if and how it worked (and don't have to reshift to undo the JPG changes). We can actually see the image results now, instead of crude wishful guessing before we take the picture.
Even if we did get it right in the camera, we still have to get it into Adobe, and there will be differences then. The one advantage of setting WB in the camera is that then it affects the preview image we see on the camera rear LCD, and it affects the camera histogram too (important, but camera Auto WB is good enough for those). It seems simpler and better to just adjust it here in raw in the first place, after we can see it, and judge how it worked.
This WB menu omits most options for JPG files since the camera has already applied something, but we do still have the good raw tools now to adjust and correct JPG too.
Adobe says tungsten WB is 2850K, the Nikon camera manuals say theirs is 3000K. Adobe sees it as 2900K. Not much difference, but these values are of course just standard guesses applying to any image involved. The values have nothing to do with the actual image or the color of the light present. These give the same constant numerical settings for any image, incandescent or not. Just an initial guess, sometimes ballpark (bright sun is normally the only one usually right).
Same raw image, camera WB Incandescent, using Adobe WB Tool on white card. 3400K Tint +4.
The Adobe WB tool was simply clicked on the white card, which has adjusted color to make the white card values be neutral now - with no color cast in the image (because the card was in fact a known neutral color). Or clicking this white paper background (3400K Tint +2), or on the white cup (3400K Tint +7) would do very much the same (click toward the light, not in the shadow). White balance can be easy. Clicking around nearby can always shift 50K or 100K, normal tolerances. The range of the Tint slider is ± 100. The cup shadow shows the light is coming from a rather severe angle, from high from the side, but the card is in the light, and still works. The image is not brown or blue, and since the subject is all white, now the histogram peaks are all aligned.
In raw images, it could not matter less what the previous WB was if we are going to change it, since there is no WB in raw files. Nothing has to be undone here, no radical reshifting of the JPG data is necessary, we can simply just set the WB we think right, that we can see is right. We can change WB a dozen times now, and all that ever happens is that the one final choice is applied once to the virgin raw data. Sure, we should avoid the dozen tries shifting a JPG image back and forth, except here, Adobe ACR uses lossless edit for JPG too (see Why Shoot Raw?).
Normally the white card is used only in the first test image, and then removed for the shoot. Later we can simply select all session images (those in the same light) and click the card in the test shot, and all session images are corrected, in one click, very fast. How easy can it be? It's really good to be able to see what we are doing.
This card is a Porta Brace White Balance Card, $5 at B&H. It works in Adobe Levels (Photoshop and Elements), but it works best in ACR (raw in Photoshop, Lightroom, and Elements). Many other editors also, even Picasa has the WB tool (called color picker).
The WhiBal card is also very good (a light gray color), arguably better technically because of claims about verifying the neutral color of its pigments (but the Porta Brace card has no pigments to worry about). I have a couple of each, and there are mild variations, but I prefer the white card. Typically a portrait subject holds it at their chest in the first test shot. Clicking around on any SAME card will show slight variations, too small to matter. Or 18% gray cards "work", usually pretty well, but they are too dark for this (dark does not show color cast as well), and are not really neutral color controlled.
When you are unprepared for WB, and suffer difficult cases, often white things already in the scene work pretty well - paper, envelopes, signs, T-shirts or white collars, a white polka dot on the pajamas, table cloths, porcelain plates, church steeples, picket fences, etc, etc. You're missing out big time if you don't realize this (see more). Notice the white things, but not all such are neutral white though, and the known special card works best, most reliable.
Same raw image, camera WB Incandescent, selecting Adobe Auto WB. 3550K Tint +5.
Auto is Auto of course (a dumb computer, no brain), but Adobe Auto White Balance sometimes has advantages over the camera Auto. One difference is that the image is cropped here, but that is not affecting this one much this time. Adobe is not far from correct this time (not always true). But of course the point of being here is that we can simply just fix it right now.
Auto cannot recognize the scene, or the light, and has no idea what it is or what color it should be. It is an impossible problem, and cameras have fancy secret algorithms for Auto WB, but basically, they seriously blur the image to be one grayish color everywhere, and then they apply correction to make that color be neutral (equal R G B components, no color cast), assuming all scenes ought to average that way (but they don't). Expodisk works that way too, except it is aimed at the dominant light source, not the subject. Camera Preset WB instructs to aim the camera at a known white or gray card. Otherwise, the camera does not even know what the image is, so Auto WB has to be guarded, wondering what if that were all green foliage, or all blue sky, whatever? Meaning, they need limits to not go too far.
Computers can easily remove a color cast to make any spot become a neutral color. What they cannot do is to determine what should be neutral. But with human assistance to provide that knowledge correctly, they can be awesome.