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RBG to CMYK, Where is my blue??

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neuromancer:

--- Quote from: Frostillicus on February 25, 2003, 10:53:35 am ---
--- Quote from: PoDunkMoFo on February 25, 2003, 01:38:39 am ---Basicaly the other post has the idea.  The human eye can see a huge range of color, your monitor can display a smaller amount of the range you can see, and a cmyk printer can print an even smaller range than your monitor can display.  We won't even go into the fact that monitors and printers use different methods to create colors (sorry I said I wouldn't go into it).


--- End quote ---

Actually the human eye can only see about 10,000,00 colors (only!) and the computer, at the standard 24 bit color depth can display 16.8million colors.  Your statement is true if you set the color depth to 8 or 16 bit.


--- End quote ---

Irrespective of bit depth, there are many colors the eye can see that cannot be produced on a monitor. There are also colors the monitor can make that the printer cannot, and colors the printer can make which the monitor cannot.

With 24 bit color, there are only 256 shades of neutral grey. The eye can distinguish many more shades than 256, especially in a smooth gradiation. You can see this to spectacular effect in photos of sunsets, where there are pink and orange bands of color.

My guess is that such a radical shift in colors is likely due to a color profile being mixed up or improperly specified.

Bob

RandyT:

--- Quote from: neuromancer on February 25, 2003, 11:30:54 am ---... and colors the printer can make which the monitor cannot.

--- End quote ---

This I have trouble agreeing with.  Typically, a printer has a much smaller color gamut than a monitor.  This gets better with more inks, dye sublimation and high resolution, but the monitor is still the more capable device  (we're talking a good monitor, not the $79 special :) ).


--- Quote ---My guess is that such a radical shift in colors is likely due to a color profile being mixed up or improperly specified.

--- End quote ---

Maybe, but there are definitely hard limits on what colors can be reproduced based on a number of variables.  

1) The cast of the paper.
2) The gamut of the CMYK inks being used (they aren't all the same)
3) The dot density/gain/bleed
4) The abilities of the driver and/or RIP
5) etc.....

PDMF:  All files sent to a 4-color printer are sent in CMYK format.  If you have a properly calibrated setup, conversion of an image to CMYK should get you a close idea as what to expect from the printer because it will use the gamut of the inks and only show what can be produced.

When you send an RGB image to a printer, the driver or RIP will do it's best to convert that information to CMYK.  If the driver or RIP is improperly calibrated the results will be poor.  But RGB or CMYK, the gamut of the inks is always the limiting factor, even on the best of setups.

RandyT

gui_999:
So should I put the 2 version of my CP on a single 8"X11" and do a print test, then compare?

RandyT:

--- Quote from: gui_999 on February 25, 2003, 02:38:01 pm ---So should I put the 2 version of my CP on a single 8"X11" and do a print test, then compare?

--- End quote ---

If you go to a normal printing shop (not a franchise) you can usually take along a sample of what you want the print to look like.  What they will do is load your file (and in this case, an RGB file is preferable) and tweak it to look like your print.  

Since they will most likely have a well calibrated system, what they see on the monitor is usually pretty close to what comes out of the printer.  So they can visually adjust the image on-screen to get it close to the sample print you provide.

Some places don't want to be bothered with this kind of stuff, but the smaller outfits are usually pretty good at trying to accommodate.

RandyT

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