Raw lets you set white balance afterwards; a grey card tells you what to set it to. The first is a freedom, the second a reference, and a set lit by mixed sources needs the reference more than the freedom.
Raw and a grey card solve different halves of the same problem, which is why shooting raw does not retire the card.
What raw gives you
White balance as a setting applied at development rather than baked into the file. Nothing is lost by choosing later, and that is a real advantage over a rendered file.
What raw does not give you
The correct value. Choosing later still means choosing, and “later” is usually in front of a screen whose own calibration is a variable. A neutral surface photographed under the same light removes the guess: you sample it, and the rest of the set follows.
Where a reference frame earns its place
Mixed light. One daylight panel beside one tungsten lamp gives two casts in one frame, and no single white balance corrects both — eight titles in this catalogue publish a colour temperature, and the bi-colour panel among them publishes a range precisely so it can be matched to its neighbours. A reference frame tells you which cast you actually have.
What no card publishes
How neutral it is, in most cases. The neutrality is the product and it is rarely quantified, which is one more reason this site reports what a listing states rather than what the category implies.
What people ask before they commit
Cannot I just correct by eye?
You can, and the result is a judgement rather than a measurement — which is fine for one picture and unreliable across a set shot over an hour as the light changes. A neutral reference in the first frame of each lighting setup gives every later frame the same starting point.
Is a white sheet of paper good enough?
Rarely, because paper is usually brightened to look white and is not neutral across the spectrum. That is the whole point of a card sold for the purpose: its neutrality is the product. Whether a maker publishes a figure for that neutrality is another matter, and most do not.
Last reviewed 12 September 2026