Asman, Andrew J wrote:
compared to the Gretag Spectrolino is consistently under 2. However, if I measure pages using a printer that has a larger gamut than the one used to create the profile, then the out-of-gamut colors tend to produce extremely large max delta E value ranging anywhere up to 100 depending on the printers used.
It's no surprise that extrapolation is much less accurate than interpolation, and that the further away from measured values you get, the worse the error.
Is there any way to increase the accuracy of the profile when faced with out-of-gamut colors?
I'm surprised to hear of delta E's as large as 100, unless you are significantly out of gamut. The best way of addressing this issue is simply to expand the gamut of your test chart to include these colors. The other approach is to try and choose a model that better represents the underlying characteristic of the device, rather than being as general as clut. You could try shaper/matrix, or gamma/matrix for instance, but you will probably be trading off a worse in gamut fit for a better out of gamut fit. This is assuming that the scanner has an underlying behaviour that is close to a per channel compression curve... Graeme Gill.