« on: April 25, 2013, 09:26:42 AM »
At a guess (I don't claim any specialist knowledge here) I think you have to be pretty accurate on your exposure when shooting the colour chart - if any of the patches are blown out in any of the channels the resulting colour profile won't be 100% accurate. Maybe better to underexpose slightly when shooting the chart than to overexpose? I usually bracket my shots and then choose the best exposure to create the profile from.
I really thought an external lightmeter would get the exposure perfect. Although I have seen that the CC gets exposed differently under different light even if I use the meter, not sure why.
But the patch with red, purple pink etc are very far from being blown (the others also). I also use low iso settings to avoid color contamination.