Can you print RGB? A kind of unavoidable question when you are working in a printing house. Unfortunately, a simple ‘yes’ or ‘no’ won’t make an accurate answer. The matter is too complex for that. Let us try to explain it in as simple terms as possible. Note that there will be some oversimplification.
What is CMYK?
CMYK is a colour space used in multicolour printing. All the colours we can reproduce in print come from combining the following four basic pigments in the appropriate ratios:
Cyan (C, a shade of blue)
Magenta (M, a shade of pink)
Black (K, which stands for ‘Key colour’).
Theoretically, CMYK could be shortened just CMY, because the black colour can be obtained by mixing Cyan, Magenta and Yellow in equal quantities. But that’s just theoretically. The resulting black is not satisfactory with its greyish brown shade, so unlike a nicely saturated black. And the method is uneconomical; it’s cheaper and more reasonable to use black ink instead of mixing 3 others to obtain an unattractive and expensive blackish shade.
What about getting white in CMYK? You’re right; it is impossible. There’s no way to obtain a white shade by combining any other colours. The white in CMYK is the colour of the printing substrate.
What does RGB stand for?
RGB is also a colour space, but this one is designed for the screens of your computers or smartphones. RGB uses three basic colours of light:
Each pixel displayed on an RGB matrix consist of three subpixels emitting light in the colours. The light produced by a pixel depends on the intensity of the light emitted by the three subpixels. If they all are lit at a maximum intensity, they produce white. If none of them is lit, the result is black or – in other words – no light.
RGB vs. CMYK
CMYK and RGB are like two different languages used to describe the same reality. The hard part in printing is to translate an RGB image into CMYK as faithfully as possible, so that the customers see the same results on their screen and on the hard copy. Considering that RGB offers a much wider range of colours than CMYK, it can be a challenge. The human eye sees a lot more colours than we can produce with CMYK. Some colours we see on screen are simply unreproducible in print. This should be kept in mind when designing your publications.
Let’s have a look at the examples below. Note the graphics on the right – it is a simulated printout of graphics automatically converted from RGB to CMYK.
What will happen if we send a file in RGB for printing?
Nothing terrible, in theory. The RGB scheme will be automatically converted into CMYK. However, you can never be completely sure of the end result. Having received the print, the customer could be a bit surprised at best and disappointed at worst.
So, does this mean you can print RGB?
Yes, but… . You must be aware that the image you see on your screen will differ from the one on paper. The CMYK palette is not as rich as in the case of RGB. Automatic conversion sometimes does not produce satisfactory equivalents of the colours. As a result, the printed colours will be muted compared to the digital original. Also, neon colours cannot be reproduced with Cyan, Magenta, Yellow and Black.
If we design in CMYK, the colours will be fine in print, right?
Our printing process engineers wish it were so simple. There are more factors that contribute to the way colours come out in print. One of the key things is the monitor itself. Colours are displayed quite differently on different monitor screens. Sometimes it is a matter of matrix quality, and sometimes of calibration – adjusting the screen to display the colours as closely to the standard as possible. Firstly, even a professional monitor can misrepresent colours if it is not correctly set. Another thing to consider is the guidelines of the printing house as regards colour profiles. Some printers, including ours, prefer files without a colour profile attached. If you send one in anyway, it will be disregarded in print. Thirdly, if you insist on a perfect colour representation in print, you can provide a specimen of your printed product (e.g. a book from a previous print run). Having a colour specimen in hand will enable the printer to achieve the required scheme.