correcting white balance in raw: loss of quality?

One of the advantages of taking pics in raw is that it gives the possibility to correct the white balance by using the raw convertor. But I wonder if these corrections create a (small) loss of quality, or not.
Even a raw file must contain some colour information. The colours of the objects we see differ depending of the colour temperature. A red flower in the evening sun looks different than a red flower under a cloudy sky. The colour temperature of the ligth affects the colours of what we see and photograph.
So, is there a limit in the corrections of the white balance we can make without losing some quality?

I think the Raw file captures what the sensor saw - the colour balance is applied after that so I don't see how quality could be affected.

Well, yes, at least in extreme circumstances. If the colour temperature of the ambient light is extreme then this can cause issues. For example, if the light is pure red, then you'll have big problems recreating blue and green (because there's no blue or green reflected back and therefore nothing sensed on the CCD).

In practice though, there's no problem. In natural light you'll not have a problem. In some artificial lights you can still get a colour cast even when WB is set...

but then with RAW you've got an infinitely better chance of getting the result you want

(I've even seen one architectural photographer use a single RAW file, and output multiple TIFF files for the WB of each lighting source - outside, inside, and other light sources - then blend them all in Photoshop. Great result!)

Matt

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I was thinking: because the sensor "saw" colours with a certain colour temperature. Maybe that could affect the quality of the final pic, if you have to make huge corrections of the white balance?
I don't know...

To a certain extent, the sensor has a "native" colour temperature, that is, the colour temperature which results in RG and B amplifications of 1.

However, this applies just as much in camera as it does in the RAW converter. The RAW file contains the data as it was captured, before white balance was applied. Any settings such as White ballance, sharpness, contrast and brightness have no impact on the RAW data whatsoever, except that they are stored as metadata to be applied later.

In short, taking a shot in RAW with WB set to Daylight and switching to Tunsten in software later will produce PRECISELY the same image as taking the shot in Tungsten to start with, except that you have more options for tweeking the WB in your converter than you do on the camera.

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