First, let’s bust a myth – there is no such thing as printing in RGB – RGB is a method of reproducing colour that is used by light emitting devices, such as your computer monitor. We won’t get too technical with this discussion, but let’s just say that when your image is set up in RGB colour mode, the pixels are assigned values that work nicely with a device that displays colour in RGB mode.
Paper doesn’t emit light, it reflects light so a completely different process has to be used, and in most cases, we use the CMYK process.
Both RGB and CMYK have a limited colour gamut, and that gamut is not the same for both – there are some overlaps, but there are some areas of the gamut that just isn’t available in cmyk, but is in RGB. So there will always be a difference between what you may see on your computer monitor and what you see in a printed page (quite apart from every computer monitor displays differently, and every printing press lays down ink slightly differently).
So, we now know that there are differences between monitors and presses, the trick now is to manage that difference as best we can.
The first step is to make sure your design file is set up in cmyk mode. Now, when you view the file on your monitor, it won’t be showing it to you in cmyk, but instead, your monitor will be emulating what it thinks cmyk will look like with the particular colours that are in your file. Basically, it’s putting a profile on your file and showing it to you in an altered state to make it look like it will look when printed on paper.
This is a valuable step, because if your monitor is well calibrated, you will get a fairly good feel for the end result. For example, if there are some shades of blue in your design that aren’t available in the cmyk colour gamut, your design software will convert the colours to the closest available shade of blue within cmyk and then it shows it to you on your monitor in approximately the colours you can expect to see on a printed page.
If you don’t like the shade, then you have the option of doing some adjustment to it, like lighten or darken it till you have a result you like.
When you’re working in cmyk mode on your computer, think of it like the computer is limiting your output values on your screen to only those colours available within the cmyk environment.
Of course, you might not be all that fussy and you just want to design in your systems default mode (RGB). Just be aware that when it comes time to print your file, if you’ve supplied it in RGB mode, we will have to convert it to cmyk. We think you are the best one to do that conversion as you will see what the difference is and will be able to make some subtle tweaks if need be. If we convert, it will just be a blanket conversion, letting the RIP (raster image processor) do the conversion.
If you want to be absolutely certain about how your file will turn out, ask us to print a proof. It’s the best way to be sure, but only do a proof if you’ve converted to cmyk first, otherwise you’re going to have issues if you need to make adjustments after seeing the proof.