Demystifying RGB and CMYK
If you’re a new graphic designer, you might get a sinking feeling the first time you hear a printer say something like, "I want full color images sent in CMYK. If you send them in RGB, I’ll have to charge extra" – and you have no idea what he’s talking about.
Here’s what he means:
RGB and CMYK are color models (aka in PhotoShop as "color modes"). They are simply two different ways of describing the millions of colors the human eye perceives.
RGB, which stands for Red/Green/Blue, is an additive color mode. RGB is the way colors on your monitor are described … and it’s the way most digital cameras record colors.
CMYK is a subtractive or reflective color mode. It describes colors that are based on mixing Cyan (a deep blue), Magenta, Yellow, and blacK inks. It’s "reflective" because your eye perceives photos and color pictures as light that is reflected off the image’s surface.
It’s important to know that when you’re converting from one mode to another, you’re not changing the image, only the way the colors are described.
You don’t have to know the theory behind all this. All you need to know is how to convert images from RGB to CMYK and back. This is what you do:
Open your color image in an image-editing program like Photoshop. In Photoshop, click on the menu item "Image." Mouse down to "Mode" and (still holding the mouse button down) click on "CMYK Color."
Other image-editing programs work pretty much the same way. Check the documentation.
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