- Grayscale with RGB values?
- Posted by Frank Kolwicz on March 4th, 2004
All I want to do is check my scanners handling of gray tones in color.
I've bought and tried Stouffer and Kodak grayscales, both opaque and
transparent, and I have no way of telling just how neutral they are
(the opaque ones are obviously brown). This seems to be the case of
the IT-8 color charts, too: the ones I've seen have brown "gray"
scales.
A grayscale with calibrated colorimeter or spectrophotomer RGB values
would be perfect, but I haven't been able to find one. I know
individuals are making them in testing inksets for dedicated B&W
printers, but I can't find any for sale.
Suggestions? Reply here or to kolwicz@efn.org, my Google address is
dead and I can't access my settings to change it at the moment.
Thanks,
Frank
- Posted by Mac McDougald on March 4th, 2004
In article <e75f0aff.0403041344.340af16a@posting.google.com>,
bb389@lafn.org says...
Well, with a RGB scan of your grayscale references, Adobe Photoshop (or
Elements) has Info palette, shows exact blend of RGB anywhere you run the
mouse over, even pixel by pixel, if want to zoom in that far. If not
equal values of each, then will quickly show what the bias is. I suppose
some other image editors may offer the same?
Or have I misinterpreted your quest?
--
Mac McDougald
Doogle Digital - www.doogle.com
- Posted by Jim on March 5th, 2004
Perhaps he means that a scanned image of a gray scale does not show equal
RGB values. Once upon a time I decided to scan the Kodak 18% gray card, and
I found that even though the image looked gray the RGB values were not
equal.
To me, it just showed that you are not supposed to scan those things because
they look different to a scanner than they do to film.
Jim
"Mac McDougald" <doogleREMOVE_THIS@netzero.net> wrote in message
news:MPG.1ab199d3f93b9bcb1ff1@news.individual.net. ..
- Posted by Mac McDougald on March 5th, 2004
In article <mxS1c.7622$HH4.5@newssvr23.news.prodigy.com>, j.n@nospam.com
says...
That was what I though he meant.
And the Info tool would point that out.
Mac
======
- Posted by Bart van der Wolf on March 5th, 2004
"Jim" <j.n@nospam.com> wrote in message
news:mxS1c.7622$HH4.5@newssvr23.news.prodigy.com.. .
Those Neutral gray references only reflect/transmit equal amounts of the
incident light (reduced silver, or carbon, usually offers such broad
spectral uniform absorption). If the light isn't seen as neutral to the CCD,
then the values will differ. However, in linear gamma, the relative
difference must be (close to) equal for all luminances/brightnesses covered.
IT8 targets don't really have to be exactly neutral in their GS steps,
because the deviation is given in the reference data file. However, they
should preferrably be close to the standard values, because that will give a
good spread of hues and luminances and allow better interpolation.
Bart
