Media-neutral in theory and practice
The development of a logo or a whole corporate design for different media will need some thorough consideration. When selecting colours, care should be taken that these can be displayed in all media. So primarily on the monitor and in offset printing, sometimes also as adhesive film, wall paint, neon ad and so on. It should also be noted that not every technically reproducible colour is also optimal for every application. In four-colour printing, for example, a colorimetrically accurate conversion of a given hue (for example, from an sRGB, Lab or HLC fan) usually requires halftoning, so that C, M, Y, and K printing inks are not being printed as full-tone but rasterized. This can result in raster effects that may cause problems in certain cases. A classic are fine fonts or thin lines which appear with jagged edges or even partially disappear. This looks very unprofessional. When designing, you should therefore plan in time how the design can be well implemented in practice.
To keep the example of fine fonts: If it is clear in advance that a word mark or text font will frequently be reproduced as a rasterized colour shade in print, it is better not to choose a contrasting font with finest lines and serifs à la Bodoni or Didot. If it has to be such a font, then use it only as solid black.
If a small font size and a light colour cannot be avoided, then only a corresponding spot colour ink will result in a satisfactory print image. For example, you might think of terms and conditions that are printed on the back of a letterhead or invoice form. To ensure that the back print does not interfere with the front side, a light gray or other bright hue must be used. Depending on where and with which equipment this product is printed, a spot colour used instead of the standard CMYK inks can lead to considerable additional costs. Or it can prevent a more cost-effective production through an online printing service altogether.
Peculiarities of the halftone screening process
Another possible source of the problem is the hue itself. If you are using RGB or Lab colours on the screen, you should consider that the conversion into CMYK may yield a pale and/or muted appearance after the screening process. This is especially the case when none of the primary colours reaches (almost) 100% ink coverage and when some black is added through the colour separation settings. In such cases you have to decide whether the accuracy of the hue has priority over a pure, saturated reproduction in the printing process or vice versa. In the latter case, you might start with the choice of a colour with CMYK values that are optimal for the preferred printing condition (e.g. for coated or uncoated paper in sheetfed offset). In the second step, a suitable media-neutral definition can then be derived in RGB or Lab. But be careful when the media-neutral colour is later converted back to CMYK or converted for a different printing condition. Then, depending on the rendering intent or the separation settings, a colour contamination may occur against the original CMYK values. The most elegant way to implement such specific colours is through device link profiles; However, this requires expertise and appropriate software. Well, the lament is on a high level. For normal users, the advantages of a uniform reproduction of media-neutrally defined colours clearly outweigh the drawbacks. Thanks to state-of-the-art technology such as fine or FM screens and high register accuracy in printing, a few percent of colour contamination will rarely catch the eye. And purists can again rely on spot colours instead. If our vision of free colour prevails, colours defined in sRGB or Lab may perhaps be readily available as custom-mixed inks in the future in order to achieve an exact colorimetric consistency. With the rather limited selection of spot colours available today, a certain deviation may have to be tolerated at times.
Eric A. Soder, Polygraphic Engineer, Uster (Switzerland), 4/2017 – polygrafix.ch