On 01/08/07, Henry G Belot wrote:
> Paolo:
>
>>; ...i find a bit frustrating ever time to calculate
>> Coord_color/255*100 and ever i've defined a color with decimal
>> (D) or hex (#) coordinates. mental-laziness issue. ;)
>>
>
> For color conversion between systems, try this link:
> http://web.forret.com/tools/color.asp?C=0.47&M=.59&Y=.99&K=.42. It
> provides an on-screen calculator for converting between various color
> systems, including the web, and links to background information.
>
> I believe your original complaint about percentages vs. decimal
> numbers is valid as it pertains to RGB color definitions. It's usual
> to express these as numbers between 0 and 255, and I also find it
> annoying to have to translate them to percentages. I'm often trying to
> match a color from an image and I have to take the numbers from my
> paint program's color picker and convert those. They look a little
> different in PageStream than in the original application, but they do
> match within PageStream itself. (More below.) I seem to remember Dan
> or Deron agreeing a long time ago that it should be changed for RGB.
>; If so, it must have slipped off the list.
>
> As for colors on screen vs. printing, without calibration equipment to
> set up your monitor to match printed output with the screen, it can't
> be done. Even then, it's problematic because print and light are just
>; different animals. That's one reason for the Pantone system.
The Focoltone system is even more useful, because it is based only on
colours that can actually be printed with CMYK inks. Pantone started
from their special spot color inks, which can't be exactly replicated
with either RGB or CMYK.
http://www.kikuze.com/focoltone/index.html
>;
> As for color-matching between different applications, I believe Tim
> Doty once told me that colors in one program should always match
> colors in another but, that's not my experience. For example, a couple
> of weeks ago I was asked to make a decision about the design of a web
> site that someone's doing for us. He put up JPEGs of several designs
> for us to comment on. Unfortunately, the one I liked best overall had
> a border with a bright green that detracted from the rest of the page
>; in my browser. I suggested desaturating that color and took the JPEG
>; into Paint Shop Pro to do just that.
>
> Well, in PSP the green was already much tamer than in my browser.
> Pasting it into another application produced a result in between. I
> desaturated the green and sent it back to him with a note to the
> effect that my version ought to look okay in a wider variety of
> applications than the original color.
>
> Windows has the capability of matching its color rendering to
> particular monitors. If the monitor identifies itself to Windows when
>; the system is installed, I believe that happens automatically.
> Otherwise, you can pick from a long list of monitors or use
> specialized calibration equipment to create a color profile. But, to
> complicate things, some applications like Paint Shop Pro also support
> color profiles independently of Windows itself. I think that largely
> accounts for the differences I was seeing between the web page in my
> browser and the same page in PSP. I know I've fiddled with color
> profiles in PSP. But PageStream, for one, renders the colors in its
> own way and gives yet another interpretation.
>;
> Then there's my main printer (Epson) which gives you control over
>; color-rendering at print time. For many photos, I have to change the
> gamma to get a good printout. It also allows you to alter individual
> colors (cyan, magenta, and so on) which I have no intention of doing.
> So, sometimes you have to experiment and plan your colors for the
> medium where they're going to end up while accepting that it's going
> to be different from what you see on your screen.
>
We really need CMYK monitors.
I remember some talk of an experimental one some years ago, but it never
appeared.
If you look at the gamuts of RGB and CMYK on a CIE colour chart, they do
not exactly overlap: each includes colours that cannot be shown in the
other. The Lab colour space does have a larger gamut which includes all
the colours of the other two - but there are no Lab display devices.
Regards
--
Don Cox
doncox%40enterprise.net">doncox
enterprise.net
.
