ICC profile connection space

On 10/29/2012 04:52 AM, Thomas Richter wrote:
Am 27.10.2012 16:56, schrieb Dale:

not exactly, you can't have an absolute profile connection space and
have appearance matching, you need a reference medium for the profile
connection space, which there is

D50 would be a better choice for an ideal additive reference system, it
could be used for some systems looking beyond the visual spectrum also,
whereas XYZ is limited to the visual spectrum

D50 is not a reference system. It is a white point. XYZ is an absolute
color system - you only need a white point if you need a white point
adaption, i.e. if you want to map the scene white point to the target
(display device, printer etc) white point. Not said that you shouldn't
do that, but that's a different task and part of what a CMM might or
might not implement, for example by means of a Bradford transformation.

Of course XYZ is "limited" to the visual spectrum, that's the whole
point of XYZ - what is visible by humans. If you need color matching for
your canary bird, well, XYZ and ICC profiles are not for you. But I
believe that then the market for such technology is pretty limited. (-:





I will restate, it is the intent and working space I have a problem with
and in so the CMM

the perceptual and saturation and relative colorimetric intents are
based on an ideal print, absolute colorimetric is not,

absolute colorimetric intent might have a use case for converting
between the same devices, that is all I see

my problem with working spaces is most applications (I use gimp) don't
allow CIELAB, CIELUV or CIEXYZ working spaces

and gimp doesn't allow you to choose the connection space, I think this
is specified in the profiles not the CMM

--
Dale

Am 30.10.2012 12:50, schrieb Dale:

I will restate, it is the intent and working space I have a problem with
and in so the CMM.

the perceptual and saturation and relative colorimetric intents are
based on an ideal print, absolute colorimetric is not,

Not really. Perceptual and saturation are not based on "print", but
"reproduction by an output device". Whether that is a monitor or a
printer is irrelevant for the purpose of a CMM. Neither would I say
"ideal" because it is the job of the profile to compensate for the
non-idealness of the device. If the device and the profile do not fit to
each other, then this is not the failure of the CMM, but the vendor by
providing you a profile that is wrong.

absolute colorimetric intent might have a use case for converting
between the same devices, that is all I see

No, it is just a matter of what your intent is. Absolute is just one
possible intent, i.e. get exactly the same colors. That means, of course
due to adaption of the human eye, that the colors will look different
under different illumination, even for devices that create their colors
themselves (such as monitors), but it is of course more a problem for
devices using a multiplicative color reproduction (such as printers).

my problem with working spaces is most applications (I use gimp) don't
allow CIELAB, CIELUV or CIEXYZ working spaces

Huh? First of all, the choice of the PCS does, ideally, not change the
rendering. The PCS is just the coordinate system within which the
profiles are specified, and the PCS is used as a common fixpoint between
input and output device, nothing more. Thus, up to numerical errors,
whether the PCS is XYZ or CIELab shouldn't make a difference, just that
some profiles and rendering intents are more easily expressed with
CIELab than XYZ.

Second, if gimp is your problem, why not report to the gimp authors?
Nobody here can help you with the deficiencies of gimp (only 8 bit per
sample, no ICC support). You can either a) report to the gimp team, or
b) supply patches to fix the problem, or c) use another program, but
your approach d) complain about it here is not very efficient and won't
help at all.

and gimp doesn't allow you to choose the connection space, I think this
is specified in the profiles not the CMM

Why should gimp do that? And what would be the purpose of that? Yes, the
rendering intent is in the profiles, but it is up to the CMM to support
other ones and reflect the choices of the user. Once again, the PCS does
not encode a rendering intent, nor should it make any visible difference
- it is only a coordinate system.

Second, gimp doesn't allow you to use a fully calibrated color workflow,
it only operates in the 8bpp "color space" your monitor seems to have.
But if that's your problem, I suggest to buy more professional software
that offers support ICC profiles.

On 10/31/2012 03:40 AM, Thomas Richter wrote:

Why should gimp do that? And what would be the purpose of that? Yes, the
rendering intent is in the profiles, but it is up to the CMM to support
other ones and reflect the choices of the user. Once again, the PCS does
not encode a rendering intent, nor should it make any visible difference
- it is only a coordinate system.

okay the PCS isn't the problem alone, but the PRM, print reference
medium is, and the PRM is what you get in the PCS unless you choose
absolute colorimetric intent

I think ProPhotoRGB PCS was chosen to try to deal with higher gamut
spaces, but RGB isn't the best choice, should have chosen a CIE
coordinate system, like XYZ


--
Dale

On 10/31/2012 03:40 AM, Thomas Richter wrote:
Second, gimp doesn't allow you to use a fully calibrated color workflow,
it only operates in the 8bpp "color space" your monitor seems to have.
But if that's your problem, I suggest to buy more professional software
that offers support ICC profiles.

gimp is free, and even better the upgrades are free

--
Dale

On 10/31/2012 03:40 AM, Thomas Richter wrote:
Am 30.10.2012 12:50, schrieb Dale:

I will restate, it is the intent and working space I have a problem with
and in so the CMM.

the perceptual and saturation and relative colorimetric intents are
based on an ideal print, absolute colorimetric is not,

Not really. Perceptual and saturation are not based on "print", but
"reproduction by an output device". Whether that is a monitor or a
printer is irrelevant for the purpose of a CMM. Neither would I say
"ideal" because it is the job of the profile to compensate for the
non-idealness of the device. If the device and the profile do not fit to
each other, then this is not the failure of the CMM, but the vendor by
providing you a profile that is wrong.

absolute colorimetric intent might have a use case for converting
between the same devices, that is all I see

No, it is just a matter of what your intent is. Absolute is just one
possible intent, i.e. get exactly the same colors. That means, of course
due to adaption of the human eye, that the colors will look different
under different illumination, even for devices that create their colors
themselves (such as monitors), but it is of course more a problem for
devices using a multiplicative color reproduction (such as printers).

my problem with working spaces is most applications (I use gimp) don't
allow CIELAB, CIELUV or CIEXYZ working spaces

Huh? First of all, the choice of the PCS does, ideally, not change the
rendering. The PCS is just the coordinate system within which the
profiles are specified, and the PCS is used as a common fixpoint between
input and output device, nothing more. Thus, up to numerical errors,
whether the PCS is XYZ or CIELab shouldn't make a difference, just that
some profiles and rendering intents are more easily expressed with
CIELab than XYZ.

Second, if gimp is your problem, why not report to the gimp authors?
Nobody here can help you with the deficiencies of gimp (only 8 bit per
sample, no ICC support). You can either a) report to the gimp team, or
b) supply patches to fix the problem, or c) use another program, but
your approach d) complain about it here is not very efficient and won't
help at all.

and gimp doesn't allow you to choose the connection space, I think this
is specified in the profiles not the CMM

Why should gimp do that?

because you want control over that aspect of the workflow, for instance
if an input profile asks for one thing and an output profile asks for
another it is left up to the CMM to choose the PCS



--
Dale

Am 01.11.2012 09:54, schrieb Dale:

and gimp doesn't allow you to choose the connection space, I think this
is specified in the profiles not the CMM

Why should gimp do that?

because you want control over that aspect of the workflow, for instance
if an input profile asks for one thing and an output profile asks for
another it is left up to the CMM to choose the PCS

You still don't understand the role of the PCS then. Once again,
changing the PCS should not change the rendered result. It is just a
matter of the coordinate system, but not the matter of the resulting
transformation.

Am 01.11.2012 09:53, schrieb Dale:
On 10/31/2012 03:40 AM, Thomas Richter wrote:
Second, gimp doesn't allow you to use a fully calibrated color workflow,
it only operates in the 8bpp "color space" your monitor seems to have.
But if that's your problem, I suggest to buy more professional software
that offers support ICC profiles.

gimp is free, and even better the upgrades are free

I don't get you. You get what you pay for. Either gimp does what you
need to do, then use it and be quiet. Or it doesn't, but then look for
alternative solutions. *Here* nobody can help you with gimp. Wrong place
for requesting improvements.

On 11/01/2012 06:01 AM, Thomas Richter wrote:
Am 01.11.2012 09:53, schrieb Dale:
On 10/31/2012 03:40 AM, Thomas Richter wrote:
Second, gimp doesn't allow you to use a fully calibrated color workflow,
it only operates in the 8bpp "color space" your monitor seems to have.
But if that's your problem, I suggest to buy more professional software
that offers support ICC profiles.

gimp is free, and even better the upgrades are free

I don't get you. You get what you pay for. Either gimp does what you
need to do, then use it and be quiet. Or it doesn't, but then look for
alternative solutions. *Here* nobody can help you with gimp. Wrong place
for requesting improvements.




maybe gimp people are listening

--
Dale

In article , Dale
wrote:

Second, gimp doesn't allow you to use a fully calibrated color workflow,
it only operates in the 8bpp "color space" your monitor seems to have.
But if that's your problem, I suggest to buy more professional software
that offers support ICC profiles.

gimp is free, and even better the upgrades are free

gimp isn't even worth free.

On 11/01/2012 05:58 AM, Thomas Richter wrote:
Am 01.11.2012 09:54, schrieb Dale:

and gimp doesn't allow you to choose the connection space, I think this
is specified in the profiles not the CMM

Why should gimp do that?

because you want control over that aspect of the workflow, for instance
if an input profile asks for one thing and an output profile asks for
another it is left up to the CMM to choose the PCS

You still don't understand the role of the PCS then. Once again,
changing the PCS should not change the rendered result. It is just a
matter of the coordinate system, but not the matter of the resulting
transformation.


look here http://www.color.org/v4_prmg.xalter


--
Dale