Gerhard Fuernkranz wrote:
This applies indeed to the other, gamma-adjusted space presented by the driver to the user. It certainly suffers from the problem that summing the colorant values won't sum up the actual ink amounts (but there is a non-linear relationship). I understand that this is the obvious reason why you wanted to calibrate the _raw_ space of the halftoning engine instead.
V1.1.0 colprof takes care of that if the .ti3 ends up with calibration tables embedded into it, which will be the case if printtarg is supplied with the calibration using either the -K or -I options. Similarly collink will take the calibration into account when computing total ink limits if the profiles it is given have the calibration embedded in the .ti3 embeded in them by colprof.
dot gain (or extremely high "gamma")), a wedge with linear steps in device space is likely no longer optimal (but a non-linearly spaced wedge may be more suitable).
It would certainly be easy enough to add a fudge factor that applies to the wedge steps to do this type of thing, but I don't think it substitutes for correct setting of the usable range, which is something more closely tied to print mode.
But back to the TAC calculation: While for a printer with CMYK inks only the raw space of the halftoning engine may indeed have the desired properties (i.e. laid down ink amount proportional to the colorant value sent to the driver), I'm wondering whether this still applies when light inks come into the play and the driver needs to separate e.g. the cyan channel into dark cyan and light cyan. Is the sum of the dark and light cyan ink amounts still proportional to the cyan colorant value sent to the driver then? If not, we have lost again...
Currently doing light ink separation is out of the scope of Argyll, so I haven't created a format to represent the separation, hence it's not possible to feed that into the ink sum calculations, but conceptually it would be done in a similar way to the above. Graeme Gill.