Hi,
I fully agree the good solution is to have a different profile for each illuminant,
as that would be the *only* way to get decent results.
However, there is a quick hack to do if you really don't care about precission.
Again, Hal has suggested what is the "good" way, and what I am here stating is
just quick and dirty, but anyway here we go:
There is a specialized, virtual device link profile for doing some specific tweaks.
One of those tweaks is white point translation.
cmsCreateBCHSWabstractProfile(int nLUTPoints,
double Bright,
double Contrast,
double Hue,
double Saturation,
int TempSrc,
int TempDest);Keep Bright, Hue and Saturation to zero. Keep Contrast to 1, and set TempSrc and TempDest
as the temperatures in �K of input and output white points. That function would give you
a abstract devicelink handle. Do a multiprofile transform joining input (microscope) profile, that one
and finally sRGB (or whatever output).
Regards, Marti Maria.
----- Original Message ----- From: "Hal V Engel" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, March 01, 2005 2:23 AM
Subject: Re: [Lcms-user] White balance
Dirk,
As you have found out when doing color profiles for a device everything in
the color processing chain matters and has an impact on the resulting
profile. A different light source or a light source adjusted differently
will change the profile. As a photographer I do not expect my day light
camera profiles to work with photos that were shot using tungsten light. So
I have profiles for my camera for each type of light that I might shot with
as well as for each film type. On some occasions I may shot a custom color
target for a specific shoot because I am not sure of the lighting. So there
is no easy answer as you can not reasonably expect a profile that is created
using one device to work perfectly for another similar device. Let alone for
a similar device with the light adjusted differently.
This all boils down to having a consistant workflow so that you can reproduce
the same results consistently. Since my situation is such that I only have
to deal with my personal workflow this is not a big issue. I understand how
important this is and I always follow a consistant routine so that my results
are reproducible. It sounds like you are dealing with others that may need
training to understand how this works and how their workflow influences the
results they get. In addition it may require that you have a number of
profiles that are correct for different devices and conditions.
Hal
On Monday 28 February 2005 01:22 pm, Dirk Str�ker wrote:
Am Montag, 28. Februar 2005 22:18 schrieb Dirk Str�ker:
> Hi everybody,
>
> I have a problem, which might is simple to solve, but in the moment I'm
> a bit confused and can't find a simple answer.
> Before I explain my problem I will give a short description of my setup.
> I'm working with a CCD-camera on a microscope. The color quality of the
> system was very bad, so I did some research, found ICC-profiles, color
> management...and so on (I learned a lot in the past weeks ;-) ).
> We bought software from Gretag MacBeth to create profiles for the > cameras
> and we were pretty impressed over the results. After that we found
> "littleCMS" and tried to use it to achieve the improved color quality
> directly, which worked fine.
> The problem is, that it is a common technique, to make a so called > "white
> balance" on the "illumination", the yellowish ligth of the tungsten
> halogen lamp should be white or gray (R=G=B). I understood the ICC
> color-management-technique in that way, that this is normally done by > the
> chromatic adaption tag (often the "Bradford matrix"). This is matrix is
> calculated while creating the profile.
> But not every individual microscope lamp is the same. Some people dim > the
> lamp, or the lamp is older... but everyone wants to make the pure lamp
> light gray.
> How can I do this
Oops, I wasn't ready.
Should I use "cmsCreateRGBProfile" and make a "transform" with the "normal"
camera profile + the new RGBProfile?
Maybe there is a simple solution and I'm just to blind to see...
I hope my explanations weren't to confusing ;-)
Dirk Str�ker
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