 Kim Moyle |
RGB vs. CMYK So why is it than when you send images for professional printing, sometimes they want CMYK and sometimes RGBAnd Also if CMYK is mostly the norm for printing, why do pro cameras still default to RGB and not CMYK?
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Ann Hall |
Are you sure they aren't accepting RGB and then charging extra to convert it to CMYK? That's frequently the case. I'd ask. As to why RGB instead of CMYK: RGB is for screen display, and many people prefer to work in RGB on the computer then convert to CMYK for printing. RGB also offers some advantages when working with various color and image manipulation tools (once the image work is done, then it would be converted to CMYK for printing). Generally, you get better results going from RGB to CMYK than the other way around, so having the image in RGB initially is more versatile. That is, you can get good results converting to CMYK for print, but if you need to use the image online or for on-screen presentations it's already in RGB.
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doug Nelson |
Are we talking the sRGB of Internet posting, or the Adobe 98 RGB that many contemporary scanners scan into? Do both convert equally well to CMYK? As I understand (or fail to), CMYK is a narrower gamut than Adobe RGB. Is CMYK even narrower than sRGB?
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Vince Broesch |
People see RGB, so cameras see RGB. Photo printers print using RGB. All colors can be seen/printed in RGB in theory. Where K (black) comes in is where the press, or other printer, has a problem getting a good black due to CMY inks that are not perfectly pure. So a black ink is added. Having a black ink gives the press a simple way to print a rich black, and also prevents over-saturation of the paper that would occur if you layed down 100 percent CMY. It's called gray scale replacement, where a black ink replaces equal amounts of CMY ink. The gamut of offset press CMYK does not print as many colors as RGB, especially greens, so it is best to edit in RGB, then convert to CMYK for separations for press. Just some technical junk, but it's all about the output end, the printer. The camera is RGB like people. I hope this makes some sence. Vince
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Roy Blinston |
The reason graphic designers and printers sometimes ask for your image to be sent in RGB or CMYK is this. When an image is converted from RGB to CMYK it goes through certain algorythms of conversion (in preparation for separating into printing CMYK plates). During this process the colour will change. Only a certain range of colours can be printed with CMYK (because they are inks not beams of light as in RGB). If you send an image in RGB to a Designer or Printer, this image may look very bright and vibrant on your monitor. The end result after printing could be disappointing (and hence you may get into arguments). If the designer/printer asks you to convert it to CMYK (so you can see the change in colour) this is maybe safer (for him). But many people don't know how to do this and do not have the ability to "edit" the picture to get the best results in CMYK. Hence more time is wasted discussing it and giving lessons over the phone about a very technical area. If you output an RGB file to a desktop printer it automatically converts the file on the fly into CMYK in the background without your awareness. There is no such thing as RGB inks. I am a Graphic Designer and always ask clients to send in RGB to save time. Also, if the pic is converted to CMYK but saved as a JPEG - this will not "display" properly inside email packages and hence it will appear damaged (causing more problems with time). Hope this helps.
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