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CMYK vs. RGB
- Thread starter ispfda
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If color purity/data loss is a concern, LAB color mode is preferred.
Most of the time, someone will ask for a CMYK image because they plan to drop it directly into a page layout program. They may be in too much of a rush (or just too lazy) to convert the image to CMYK.
Most of the time, someone will ask for a CMYK image because they plan to drop it directly into a page layout program. They may be in too much of a rush (or just too lazy) to convert the image to CMYK.
Hi,
All the above is correct but I wan't to add that the color range of CMYK is not as big as RGB. This is due to the printing business. It is impossible for printers to print all the nuances of the RGB gamma, so when you convert from RGB to CMYK there is a certain loss of colour between your screen and what can be printed. This is important for the separation setup. After converting to CMYK always check your channels. The Cyan channel should be a good greyscale of your colour file. The Magenta should be almost the same as the Cyan channel, the yellow channel is the trouble shooter in the CMYK spectrum, it tends to be a messy channel with a strange colour structure. If you click on the eye icon before the C M and Y channel you should have a good view of your colour picture, The Key Colour channel (or Black) is only used for depth and shadows in your colour picture. Be sure that if there is a lot of black in your colour picture that the black areas are not in the four channels, otherwise the printer will have problems printing it in the correct way, the CMY and K will be to rich and the print will be very messy due to the amount of ink used in the four layers.
But this a large question and a little bit to much to go into in this forum.
hope this helps
grillhouse
All the above is correct but I wan't to add that the color range of CMYK is not as big as RGB. This is due to the printing business. It is impossible for printers to print all the nuances of the RGB gamma, so when you convert from RGB to CMYK there is a certain loss of colour between your screen and what can be printed. This is important for the separation setup. After converting to CMYK always check your channels. The Cyan channel should be a good greyscale of your colour file. The Magenta should be almost the same as the Cyan channel, the yellow channel is the trouble shooter in the CMYK spectrum, it tends to be a messy channel with a strange colour structure. If you click on the eye icon before the C M and Y channel you should have a good view of your colour picture, The Key Colour channel (or Black) is only used for depth and shadows in your colour picture. Be sure that if there is a lot of black in your colour picture that the black areas are not in the four channels, otherwise the printer will have problems printing it in the correct way, the CMY and K will be to rich and the print will be very messy due to the amount of ink used in the four layers.
But this a large question and a little bit to much to go into in this forum.
hope this helps
grillhouse
hmmm....not sure about that one, grillhouse. The content of the CMYK channels are entirely dependant on the image. If it's predominantly red, for example, then the Cyan and Magenta channels will look nothing like each other!
As for ink coverage, it's quite difficult for this to become a problem in Photoshop just by converting from RGB to CMYK. This is because of the way Photoshop generates the black channel. Using either GCR (gray component replacement) or UCR (undercolor removal), Photoshop removes parts of the other channels and replaces them with black. You have to really delve deep into Photoshop's separation set-ups to cause problems of this nature -- most PS users probably wouldn't know, or even need to know, how to do this!
However, if you subsequently mess with the individual channels, it is possible to create the problems you describe (been there...!).
Back to the original post, though, and I would say that printing is the ONLY reason anyone would request CMYK. Many professionals keep RGB/LAB master copies, even if it's going to print eventually, because separation technology is improving all the time. If you convert to CMYK, you're pretty much stuck. If a better printing process emerges, with a wider color gamut, then it's nice to have the original files available to create new separations from. However, don't expect your printer to convert everything for you... it's not necessarily laziness -- they may only accept print ready files because that's all that was quoted for!
As for ink coverage, it's quite difficult for this to become a problem in Photoshop just by converting from RGB to CMYK. This is because of the way Photoshop generates the black channel. Using either GCR (gray component replacement) or UCR (undercolor removal), Photoshop removes parts of the other channels and replaces them with black. You have to really delve deep into Photoshop's separation set-ups to cause problems of this nature -- most PS users probably wouldn't know, or even need to know, how to do this!
However, if you subsequently mess with the individual channels, it is possible to create the problems you describe (been there...!).
Back to the original post, though, and I would say that printing is the ONLY reason anyone would request CMYK. Many professionals keep RGB/LAB master copies, even if it's going to print eventually, because separation technology is improving all the time. If you convert to CMYK, you're pretty much stuck. If a better printing process emerges, with a wider color gamut, then it's nice to have the original files available to create new separations from. However, don't expect your printer to convert everything for you... it's not necessarily laziness -- they may only accept print ready files because that's all that was quoted for!
I have read white papers on the newest technologies for printing processes. There are presses now that use six colors to achieve the same color space as RGB, however the presses are very expensive and not readily available in the USA -- Mostly in the Far East. Let freedom ring!
Six color technologies are popping up all over the place, particularly in the digital arena. I've worked with a few already. The HP Indigo Turbostream and above support it, and a Xerox large format plotter, the Vivagrafx, also has six colors. Many deskjet printers, particularly from Epson, use it to great effect. There's also Hexachrome, which I think is aimed at replicating Pantone colors.
They seem to implement it in different ways, though, and none of them seem to provide the ideal solution for every image. When it works, it works great, but sometimes it does pale in comparison to 4 colors, suprisingly enough.
They seem to implement it in different ways, though, and none of them seem to provide the ideal solution for every image. When it works, it works great, but sometimes it does pale in comparison to 4 colors, suprisingly enough.
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