^^ no. not PS levels.
I mean. Yes. Well. Maybe.
One thing I really don't like about a lot of raw processors is that it's unclear what functions are pre-conversion, and what functions are post-conversion. AFAIK, many raw processors will do levels and curve after processing leaving only channel exposure.
And that's OK. But you have to be aware of this. If your image has a white balance issue, and you're shooting raw, then it is better to correct using the white balance slider in the raw processor, because this is done before conversion and the correction may be sufficiently severe to start drawing out noise and other artifacts.
It's also important to remember that white balance is *always* applied post-exposure. For someone who shoots raw, a greycard is simply something you do not need to worry about. The camera exposes everything in the middle of the range with a linear gamma. If you look at a raw file before ANY color correction and after interpolation, it's green and appears substantially under exposed. The amount of monkeying around that raw processors do to our images is pretty astounding, in fact I've found that under normal daylight white balance the raw processor pushes the red channel by over a stop and a half.
As great as a sensor that could attenuate gain at individual color components would be, that isn't how cameras work. Setting the white balance in your camera does nothing to the exposure, it only flags the raw data to compensate for the determined conditions. In the case of a jpeg, the camera sends this into it's onboard raw processor, and combined with 8-bit data, it's really essential that white balance is set properly. When shooting in raw, it conveniently moves the slider on your behalf.
Yep. That's it.
That's all it does.
But I guess I'm not saying throw away your grey card. White balance can be tricky to set without having a good reference and digital makes referencing white balance super easy. But I do think that it's really important that people understand what white balance is actually doing, and how it differs from something like curves and levels that are typically, afaik, applied after the raw file is processed.