Impact of WhiBal 'Lt' or 'Med' Gray CWB

[T_Macaw]

Assuming WhiBal or other 'accurate' (no color cast) cards, is it correct to state that EITHER will produce a satisfactory CWB setting (defined by no in-camera compensation for color cast in the card) but if two identical images are then shot with the camera in the same lighting ... one will need 'brightness' post processing to match it to the other? ... due to L* value differences.
Your emphasis on the Light Gray card for RAW (and digital?) is clear, but the associated science is not clear (given the long-standing 18% gray card preference).
Tom B. (TMc)

[MichaelT]

The 18% cards that you mention were and are designed for setting proper exposure for film. They have nothing to do with White Balance. Regarding Light vs dark for Custom WB, each camera is different. While they are both neutral, some caemras want White, and some want Gray. I have not done tests to confirm that it makes a difference, but it is easy enough for you to test it. Just do each CWB, and then take a picture of the WhiBal. measure the JPEG in a photo editor and check the RGB values on the WhiBal card. They should be within 1 or 2 points of each other. Check each different CWB and see which is most accurate for your camera. Please post your results. I will dosome tests of my own when I return from WPPI.