Forum Moderators: not2easy
Do you have a Pantone book? Sometimes it is easier and more accurate to look at a Pantone color and match it up to your website than have the computer do the conversion. Your printer should have one, it is like one of those paint chip books at the house paint store. Then you will know which CMYK color most accurately conveys the branding of your website.
RGB and CMYK are both color spaces. RGB - a digital "computer" color space, uses the additive color mixing method. It mixes colors by adding different wavelengths. The colors in RGB are created by actively emitting light sources - like computer screens.
CMYK is an analog color space, originating from the printing industry. It uses subtractive color maixing, where the layers of paint act as a filter which subtract unwanted wavelengths and convert them to heat.
Even though you can transform RGB to CMYK with a simple formula, this leaves many aspects out. The most important thing are the different gamuts. A gamut [google.com] defines ALL the colors a device is capable to reproduce. Due to the different mixing models above, the gamuts of your RGB-screen and your CMYK-printer share only a very small common gamut. But each gamut has huge portions which do NOT overlap the other gamut.
ONLY colors in the overlapping gamut can be reproduced on BOTH devices without any change. Colors outside the joint gamut CAN NOT BE REPRODUCED on the opposing device! For example there are huge areas of blues and greens in the RGB gamut, which are simply not covered in the CMYK-gamut and can therefore not be printed.
Enter colormanagement. Color management can not overcome these limitations. Ther eis no way, colors outside a devices gamut can be displayed by that device. However, there are ways to trick the eye, to make a human watcher believe the colors are being reproduced. In order to do this, you need to change the colors in a subtle way. Most likely, you also change colors inside the joint gamut in a subtle way as well. The overall impression though is that the colors can all be reproduced, even though they are in fact all moved or shifted or transformed inside the destinations devices gamut. The process is called rendering, and the good news is that you do not need to do a lot of things. You only need to select the rendering intent, and here the best choice is to use perceptive rendering.
Yet you still need two things: color profiles. Those profiles define the capabilities and the gamut of the device you are working on. You need the source profile, which in your case is most likely sRGB. And you need the destination profile - and this one is shipped with your printer or can be provided by your service provider (e.g. your printshop). Those profiles act as a pair. When they are combined, they form a translation matrix which move the colors from one color space safely into the destination space.
However, even good color management can't do wonders. So as soon as you provide a destination profile, Photoshop will issue little warning-signs in the color-picker dialogues if colors are too far off to be printeable.
Hope that helps!
[bargainprinting.com...]
There is no way to match many RGB colors in print in 4-color CMYK. There are very good ways to accomplish more and brighter colors with 5th and 6th colors, talk to a decent litho printer and they will be able to help you.
If you look at the CMYK vs. RGB spectrum graphic here:
[dx.sheridan.com...]
you will see clearly that there are plenty of PMS and RGB colors not possible with CMYK.
So even though there are more bits per pixel in CMYK (RGB is 24 and CMYK is 32), it has a much smaller color gamut. So there are colors available in RGB that are not possible in CMYK. Use your Gamut tool in photoshop to help show what will not show in CMYK correctly. It's View-->>Gamut Warning. This helps people beginning with CMYK understand whe color limitations.
Try printing both the RGB and CMYK versions of the file, and see how big a difference there is in the output. Usually it's not much, because CMYK on your monitor is trying to "fake" how ink will look on paper, and RGB on your printer comes out actually looking like ink on paper... since that's what it is.
If your test prints come out looking OK when compared to each other, then you have nothing to worry about.
bajingan referred to working on one postcard file, and it would save a lot of time and effort if you're just converting one file between RGB and CMYK to do a quick test print.
Of course if you're doing color matching regularly, on a professional level, getting professional tools is the best idea. But if you're only doing print design ocassionally, and you mistakenly start a file in RGB instead of CMYK, checking the color conversion on your local printer is usually adequate.
Photoshop generally does a reasonable job of RBG-to-CMYK conversion anyhow, so unless you're really NEEDING to precisely match a given color, it's probably fine.
There is more to graphic production than fiddling around in photoshop in RGB...
-- Zak
1) How can I set up and use Pantone colors in Photoshop?
2) When working with Pantone colors, which mode should I set my Photoshop in? RGB or CMYK?
3) Can you do gradation between 2 Pantone colors? Can I have a drop shadow in Pantone?
4) What's the difference between Pantone Coated, Pantone Uncoated, Pantone Process, Pantone ProSim? Which one should I use?
Thank you!
You can set the preferences for your color palette to display Pantone colors, I think...?
I personally use Pantone Process most often.
Pantone are not a special type of color... It's printing ink with the CMYK values listed so you can design print material and have the on-screen image look relatively accurate to the final printed image. You can do anything with Pantone colors in photoshop that you can do with any other CMYK color...
For specifics about a specific print job, I personally prefer to ask the printer I'll be using for their specifications, file type preferences, and any other specific information. They're usually more than helpful, because it saves them time and hassle when you bring in a file that already fits in with their workflow.
