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converting rgb to cmyk

Posted on 2003-10-23
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Hello,

i am trying to convert a jpg-pic from rgb to cmyk. Actually I create a layout in freehand and i want to import this jpg-pic in my freehand-layout. Since the freehand file is going to a printer, i thought i have to convert the pic into the cmyk-format. When i change the rgb-mode in photoshop to cmyk, i noticed a change of color and appearance of the pic. So i adjusted a few settings in photoshop (brightness, color hue,etc.) and i saved the pic in photoshop-format. Now when i import the pic into the freehand layout the colors look very different than in photoshop. Why is that so?

Thanks for your help
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Question by:Chillipowder
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by:weed
ID: 9610866
For your purposes you probably REALLY dont need to convert to CMYK. That's only necessary under very specific circumstances. So basically, ignore it. Leave the image as RGB.

The change in color you are noticing is because the CMYK color space is slightly different than RGB and thus the colors must be shifted to fit into the CMYK space.

The colors probably look different in freehand than in Photoshop because your color management settings are wacky. Theyre either different in each program, or different in your OS settings than in Photoshop. If you're on windows turn OFF photoshop color management.
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by:flanque
ID: 9626139
Hi Chillipowder,

Okay the rule of thumb is that if you are printing it out, then you should use CMYK. The printer knows how to seperate the colours properly and isn't left guessing. The way you should do it to get the most accurate colour print, is work with the image in RGB format until you are ready to print. And by ready to print I mean the next thing you have to do is click on the print button.

When you convert it to CMYK it will look different on the screen, but remember that this is only because the monitor is trying to emulate CMYK on an RGB display. In other words, what you see when you open a CMYK image on an RGB monitor is not an entirely accurate representation. It's only a best guess by the computer.

A point to keep in mind is that the colour profile used as your CMYK 'range' may be a little different to that which your printer uses. This pretty much means that you are using a little trial and error with this, but generally it will be okay. Unfortunately based on my experience I think it is quite difficult to get a colour profile for Photoshop that is designed for your printer. When I was doing the graphic art for the brochures at my work, I asked a host of professional printing houses and they all told me that it would be a nice idea, but not a reality.

So, in short work with the image in RGB format until you are ready to print, then convert it to CMYK and then print. It should come out pretty accurate.
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by:weed
ID: 9628211
If youre going to an inkjet printer you dont ever want to convert to CMYK. Inkjet printers would prefer an RGB image and do the conversion themselves.
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Snazzy_Graphics earned 250 total points
ID: 9700273
Yep.

And if you are going to a commercial printer the process of matching what your image looks like on the screen to what his equipment outputs is complicated (sometimes even contentious). Like Flanque said, work in RGB. Last step is to convert. I wouldn't adjust your images based on what converting to cmyk does, unless you have a really good, callibrated monitor and understand how color works on the screen vs. paper (among other things).

Look under edit > color settings > cmyk before you convert.

There's probably only four presets which apply to you, web (coated and un) and sheetfed (coated and un). This is the printing press and paper, and how pshop will convert to cmyk. Web works pretty good for most everything to most anybody's eye. There's other settings here too, and other ways to mess around, but this is really the realm of professionals.

You can preview your settings under view > proof. Gamut is also useful. All of this stuff is interesting and functional, just a matter of how much time you want to invest in learning to increasingly remove just a little more guess work out of how your final product will print on a commercial press.

--Snazzy
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by:Knightley
ID: 9720930
convert RGB first to LAB, then LAB to CMYK. maybe a bettet result, just try it.
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by:weed
ID: 9722730
Photoshop automatically converts to LAB when switching to CMYK.
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