I need to convert many D50 Lab measurements over to D65 illuminant. = I.e, I need the new measurements to be equivalent to the measurements I *would* have measured, had I set my colorimeter to = D65.=20
This is called calculating "corresponding colors" and you use Bradford transform to do those.
As I understand it, Bradford will give you a perceptual change. If you want an approximation of the numbers your meter might have given had it been set on D65, I find that a 3x3 matrix in XYZ gives a closer result:
D50 LAB -> XYZ XYZ -> 3x3 matrix -> XYZ XYZ -> D65 LAB
You can find a 3x3 matrix by (for example) measuring a macbeth with your spectrophotometer set on D65 and on D50, and doing a least-mean square.
I see an average error of just under 1 dE doing this, with a peak error possibly much higher. For best results, redo your measurements.
John
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