Jorge Parra wrote:
<<
What I refer to as "target" values are those that come in a table of RGB
values along with the Chart.
>>
Jorge,

A while back I did some calculations comparing the XYZ and RGB values on the
Macbeth chart and concluded that they were effectively using sRGB primaries
or close. Sadly, I cannot find my notes.

One solution to your problem would be to download the Lab version of the
chart, correct the patches if they do not quite match the data for your
chart, and convert to your preferred working space. You should then have RGB
values which match your chart.

I do not recall where I found the Lab TIFF image of the ColorChecker, but I
can send you one if you need. Alternatively you can easily create your own
patches in PS using the Lab data on the ColorChecker.

I had a problem recently when I was asked to photograph a painting in the
local cathedral, with very mixed and uneven lighting. Like you I wasI using
a D60 camera. I used the Macbeth chart to get the white balance, and,
together with Color Mechanic (www.colormechanic.com), to improve the
colours. Given the extent of problem the results were good.

Tim Mimpriss


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