Re: Profile Editing
Re: Profile Editing
- Subject: Re: Profile Editing
- From: Steve Upton <email@hidden>
- Date: Sun, 21 Jan 2001 16:27:32 -0800
At 5:48 PM -0500 1/21/01, email@hidden wrote:
In a message dated 1/21/01 3:48:55 PM, email@hidden writes:
>Here are my questions:
>
>1) Am I placing too much importance on the gamut view? So far the prints
>made from the smaller gamut profile seem to look better.
The smaller gamut was in relation to your custom profile. It is not
surprising that you like the custom profile better than the canned
ones, even if it does map out to having a smaller gamut. Sometimes
the instrument used can affect this.
Yes, Steve Upton will disagree, as he is in the business of selling software
that does this type of comparison, but I find such comparisons less than
reliable. Using Steve's ColorThink tools might be a better choice, but as
Steve and I have discussed previously on this forum there are still other
factors that make the gamut surface less than meaningful.
<frown>
Well, first let me say that I am primarily in the business of helping
people get good color. We also build tools to help to that end
(journey)
Second, I believe that gamut surface can be very valid and meaningful
but it is by no means all the information that is available in a
profile. - I'll expand on that a little more below.
>
>2) Are there other factors at work here?
Yes, the gamut surface doesn't tell you where the photographic colors inside
lie, only the vector colors at the surface. Editing profiles can exagerate
the difference even further.
Photographic? Vector?
Overall I am in agreement here. Gamut surfaces tell you the size,
shape, and composition of a gamut boundary. This can be quite useful
for several color management issues but does not tell you about the
behaviors inside the gamut. "Composition" you ask? well, the gamut
boundary maps we do in ColorThink show linearity issues in pure inks
as well as other device qualities - email me directly or ask here for
more details concerning this.
>
>3) Why would the gamut of my profiles seem to expand significantly by simply
>changing the shape of the CMYK curves? It seems that I should actually
>be
>reducing the number of colors available.
This is the most interesting part of your post in my opinion. I
simulated your edit in ProfileMaker's Profile Editor and found that
the gamut map in Profile Editor did change. In my case it clipped the
green and red parts of the gamut (in 2D). When I mapped the gamut in
ColorThink it did not change at all. This shows that GretagMacbeth
are using a different method of calculating gamut boundary. AFAIK
ours should be correct and I assumed up to now that Gretag did it the
same way.
Editing a profile, especially the edit you tried, should change the
linearity of colors inside the gamut but should not normally change
the size of the gamut. Gamut size is typically set by the physics of
the device. You may be able to bump it out in some tools but this
would seem to be an error rather than a feature.
There is also the possibility that you have set ink limits in your
profile and in editing the profile you achieved higher total ink
levels. This is one method where you could increase the gamut in a
"legal" way. I would be a little concerned about editing creating
this change though. Ink limits are obviously something you want
adhered to.
Back to gamut surfaces.
As I mentioned, gamut surface maps are valid and vary useful for
device and even profile comparison. They can be used to:
- determine the behavior of a device including linearity of pure inks
as they are increased from 0-100%
- determine hue behavior of inks including the hue comparison between
light and dark inks in 6 color printers (like light Cyan and dark
Cyan)
- compare working spaces to input and output spaces
- compare two device gamuts for evaluation of a proofing system.
There is no way to proof 100% SWOP yellow on many inkjet ink/paper
combinations for instance - gamut maps show this pretty clearly. Also
many RGB-driven ink jet printers do not have enough shadow colors to
simulate Matchprint, Waterproof and other proofing systems -
something you really only see in a 3D gamut graph.
- compare image or spot colors to gamut - this can show not only out
of gamut colors but how far out and how they will map into gamut when
printed (when vector comparisons are used for instance)
and others
As I mentioned, these maps do not show linearity inside the profile
and so won't show potential banding issues, blocked shadows, etc. I
have never stated that they would do so. I have also not had any
serious challenge to the uses I mentioned above. I do welcome
discussion however. As I said, I am more interested in good color.
Regards,
Steve Upton
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