On current (late 2012) digital cameras, not only is the histogram tied to JPEG settings, the Live View display is often also tied to the choice of JPEG settings (rather than showing an image that helps one to focus!):
Most all camera manufacturers won’t even specify what the histogram incorporates, so it is best not to assume anything— test your gear and learn what the histogram means for RAW files— typically the histogram is for a JPEG with unclear or unspecified settings.
See the full discussion in Camera Histograms: Color Space, Contrast, White Balance, and related pages.
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