[argyllcms] Re: How to do this?
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 21 Nov 2017 14:21:19 +1100
Yves Gauvreau wrote:
++ Just any mixture of non equal RGB values. Not sure what you mean by
device values though?
Color defined in a device dependent way, as opposed to being
described in a device independent way. See
for an introduction to color that explains these terms.
An ICC device profile provides a means of translating between device
color values and device independent color values.
All my images are in a RGB colorspace even when R=G=B. I'm not sure I
understand the R=G=B step wedge, if this is what I need to print on my
transparencies then I already know it won't work. Even full black ink or a
neutral combination of CMY doesn't provide enough density on the negative
when using UV light to expose the print.
Well, I'm not understanding what you hope to achieve then, if you
workflow doesn't work. Unless the printer is very odd, R=G=B
is going to give the maximum range of control over all wavelengths,
meaning that you can't do any better than that using some other color.
i.e. R=G=B=0 = black, which should block the maximum amount of light,
conversely R=G=B= 100% = white, which should allow the maximum amount
of light through your transparency. Yes if your photographic process
uses a narrow band light source then you can theoretically use just Cyan,
Magenta or Yellow, but typically colorants are not perfectly transparent
at their pass band wavelengths, nor does adding C+M+Y block as well as
C+M+Y+K (assuming your printer is using K), so it should be safe
and have maximum effectiveness to use R=G=B grey.
If it doesn't work that way, you'll have to explain why, in terms
of what type of printer and transparent media you are using, and
the nature of the photographic negative process (i.e. what light
source and what photographic medium it is.)
All the methods I've seen to create
digital negative use a greenish step wedge and Photoshop curves to get this
wedge to print correctly.
Seen or tried ? i.e. do you have any evidence that green works when black/white
I suppose the calibration curve are more or less
equivalent to Photoshop curve but they are applied in a profile instead of
on an adjustment layer?
Something like that.
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