[argyllcms] Re: Ink Limiting
- From: Jason Campbell <campbell.jj76@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 11 Aug 2013 21:23:27 -0400
Nikolay,
So given I am looking to model the 0-100% CMY neutral axis, what would be your
thought on this? My requirement is to not only optimize gray balance through
the tonal range of CMY triplets (3-color gray), but the need to yield
adjustments that, at 100%, are indeed 100/100/100/0 (300%). For I cannot cut
short the honest 100% solid triplet. This is not solely an inkjet application,
and in a conventional printing application, solid must be solid. So I cannot
direct 100% to be something short of that -- which is what I am seeing from the
current profile I am generating.
Back to the original intent, I care for the neutrality to be either calculated
automatically by the profile, or through other means, and CMY builds derived
from B2A lookups for Lab values determined through other means (which I am
doing now). This is what brought this to light as when I ask for the effective
300% Lab value, I am getting a B2A that is clipped. I completely understand
your point back to me on the inherent limit imposed by the profiling engine,
but still wondering if there is a way to either force the gamut map to a deeper
black or if there is a way to scale the result?
What I mean by the last part (scaling) is can I take a synthetic profile and do
either a link or a perceptual map to it? I'd rather stay with something 'true'
to the device and simply calculate my target Lab values, then pump them into
the profile for a B2A-based CMY build. For the most part it is working as I
desire, but once I get into that sketchy 80%+ tone value area, things start to
fall apart. Mostly since the profile doesn't deliver a 100/100/100/0 result...
So currently I fudge it, but there must be a better way!?
On Aug 9, 2013, at 2:05 AM, Nikolay Pokhilchenko wrote:
> Jason Campbell wrote:
>
> Bottom line is that when I start doing B2A lookups (Lab->CMY), I never am
> able to get any further out than roughly the 270% total ink, and I really
> need to get a lot closer to 300% if at all possible… Is it?
>
> This is because Your inks didn't deliver more deep black while increasing
> their amount above 270%. The deepest black is achieved by the mixture of 270%
> of certain CMY inks and any increase of any channel value leads to increase
> the brightness of the black point.
> I recommend You to use -l410% limit for target for true no limit. Then
> compute A2B table and examine it by xicclu. You may discover that C=M=Y=100%
> is not so black or not neutral black. So the closest neutral and deepest
> black is at 270% of total volume.
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