Re: Real world experience w/ GMG and Oris RIPs
Re: Real world experience w/ GMG and Oris RIPs
- Subject: Re: Real world experience w/ GMG and Oris RIPs
- From: Graeme Gill <email@hidden>
- Date: Tue, 30 Nov 2004 01:01:04 +1100
- Organization: Color Technology Solutions Pty. Ltd.
Roberto Michelena wrote
The important thing in this scenario is that the test values are the
gridpoints themselves!
Of course you can't test all the gridpoints (17x17x17= 4,913 and 33x33x33 =
35,937) ; but if you subsample the grid (for example 9x9x9 = 729), for those
points you did not test you can interpolate the corrections ("moves") done
on the points you indeed did test. As long as you keep using the same
interpolation algorithm as you used to build the profile, it's consistency
(smoothness) will be preserved. Unless the errors were induced by
measurement noise (which is easily eliminated by averaging in the first
place), there's no reason to assume the accuracy will suffer.
And to make it better, the second iteration you can make in the points that
were untested in the first one. You could asign an "inertia" to each
gridpoint, beginning at zero, and increasing everytime it has been tested
(and thus moved) directly. That way each the second iteration has less
effect on the previously-corrected points. And so on.
Hell, I'm just throwing untested ideas. But it would seem it's doable and
beneficial, it's just a matter of defining the right algorithm and tuning
it. It's a fact that in all fields of science, measure-and-adjust iteration
helps tune the result of a not-perfectly-fitting model.
I'm not following you at all. Why would you test the B2A table with it's own
grid points ? For almost all reasonable inversion algorithms, the B2A grid
point values will be perfectly accurate. They are the inverse of the A2B table.
There is nothing to tune. (in my profiler, the inversion is generally accurate to
about 1 part in 10e6 or better).
Tuning only has any meaning at all, if you are concerned about values that
fall between the B2A grid points. Because of interpolation errors, such values
will not be perfectly accurate. They might be made more accurate by moving the
grid point values around, trading off decreased accuracy at the grid points,
for improved accuracy between the grid points. If the "between the grid point"
values are a particular test set (say an ECI2002 charts values), then the
rendering for those particular chart test values might be improved, at the cost
of poorer accuracy in other areas.
Graeme Gill.
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