Re: Sony Artisan 1.2 Colorspaces Question
Re: Sony Artisan 1.2 Colorspaces Question
- Subject: Re: Sony Artisan 1.2 Colorspaces Question
- From: Roger Breton <email@hidden>
- Date: Tue, 02 Sep 2003 11:59:37 -0400
Bertho,
>
Obviously we have a definition or measurement problem. Here are a few
>
thoughts:
>
If a white sheet is measured and it is them substituted with a sheet that is
>
printed all black, the ambient illumination will vary because of the change
>
in reflected light that will re-radiate onto the sample. The re-radiation
>
depends on the surrounding environment.
OK.
>
I assume that the meter you are using is a spot meter.
Yes, 1 degree, according to Minolta's specs.
>
Is it by chance
>
picking up light outside the defined spot? What about moving the meter
>
closer?
Tried moving the meter closer but the measurement remains the same.
>
What happens if you move the 1000W lamp to different positions?
It does change the Illumination received on the sample, for sure. But the
ratio of substrate's Luminance to 350% CMYK patch remains constant.
>
I would expect the best way would be to have a checker pattern printed and
>
then use a spot meter with a physical shield and to verify that adjacent
>
light from a bright patch is not affecting the reading of the black patch.
You think flare is lowering my pure substrate Luminance reading? I don't see
flare being a factor in my measurement geometry as the instrument's optics
effectively restricts the cone of light to a 1 degree angle of acceptance.
>
Would not the ultimate test be to measure reflectivity vs. wavelength and
>
then plot contrast vs. wavelength? That would visualize what is happening.
You mean percentages of light reflected at each wavelength? That's easy
enough for the sample press sheet but how would you compare that with the
emission of the monitor? Let say you have a spectroradiometer that gives you
absolute power measurements of Watts/sr/m2 for the monitor. You take a
reading of white and then black. (btw, I've already made spectroradiometric
measurements of my monitor with a Minolta CS-1000 of white and black if
you're interested). Then what? The first quantity, spectrophotometric
measurement, is already a 'contrast' metric, light emitted by the
instrument's light source vs light reflected by the substrate. The second
quantity is absolute power. How do you propose to relate the two quantites
meaningfully?
>
The paint is made by Behr: 1050 Ultra Pure White; Interior Flat
So it's a paint brand. Thank you. I'll make a note of that.
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
_______________________________________________
colorsync-users mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/colorsync-users
Do not post admin requests to the list. They will be ignored.