WB limitations on D40?

[criscross79]

Ok, so I was looking at Ken Rockwells site today and came across this quote about setting manual white balance

TRICK: Set it pointed at something colored or through a colored filter and your resulting photos will have a color cast opposite the color to which you set it! Set it on something blue and photos come out yellow, set it on something purple and the photos come out green. Point it at something warm and you get cool and vice versa

Well, I thought to myself, that sounds pretty neat so I tried it on a cloudless sky. but my camera came back with an error and said it couldn't capture it, try again. just to make sure it was working ok, I tried setting the WB with a gray background and a white back ground and both worked fine.

Is their a limitation to the color range used for the manual WB setting on the D40?

Thanks,

Chris

[cyclohexane]

Even for WB targets, you need to make sure the exposure is correct. The camera probably felt your exposure for the sky was totally off, and wouldn't use the reading.