It makes absolute sense to work with Lab colour definitions and values in the design, because these define a colour in an output-neutral way. A company logo, for example, should be created in such a way that it can later be implemented in various ways, e.g. in print, on the website, on vehicles and textiles without any problems. This is common practice and the Lab colour definition offers the neutral prerequisites for this.
Unfortunately, this is still wishful thinking in most cases. Most graphics programs allow Lab colours, but these are often lost during PDF export and almost always also when an object is to be further processed in another software. PDF files and file export/import are common, however, because printers expect PDF data and designers do not work in a single software but with several tools for the application areas of layout, graphics, image processing etc.
Example Adobe Illustrator
Man kann in Illustrator zwar zunächst eine Farbe in Lab anlegen, die Lab-Information wird jedoch in RGB/CMYK gewandelt, sobald der Farbton bestätigt wird und in die Farbliste wandert. Mit einem Trick ist es trotzdem möglich, Lab-Farben dauerhaft in ein Dokument einzubinden: indem man sie als sogenannte „Volltonfarbe“ erzeugt – sodann tauchen sie in der Illustrator-Farbpalette als Separationsfarbe mit dem Alternativfarbraum Lab auf und werden beim Export der Datei in andere Dateiformate (EPS, PDF) auch so beibehalten.
Example CorelDraw
CorelDraw allows you to work with any number of Lab colours and works well with this, but the unchanged export of this Lab vector data to other software is not possible. Objects created in CorelDraw neither as EPS nor as SVG keep their Lab colour definition, but they are saved in the RGB variant just set. CorelDraw cannot even save Lab data in TiFF, PSD or PDF files - not even in the very latest 2018 version.
Example Adobe Photoshop
In Photoshop, the use of Lab as a document colour space has been quite possible for many versions. Colour lists in Lab format (ASE libraries) can also be read into Photoshop, and if one uses these colour tones in a Photoshop document, their Lab definition remains (when exporting to other formats, however, only if the document colour space is Lab or the Lab colours are created as spot colours).
A suitable exchange format for Lab bitmap files created with Photoshop is the TIFF format. Lab TIFFs can be integrated into layouts created in InDesign, for example, without any problems. Even a PDF/X-3 or PDF/X-4 created with Photoshop without colour conversion to the output destination still contains Lab data.
Example InDesign
Ännlich ist es beim Layouten mit InDesign. Farben können in Lab definiert werden, Lab-Bitmaps können eingebunden werden, und exportierte PDFs können ebenfalls Lab-Farbtöne enthalten. Beim PDF-Export bleibt eine Lab-Farbe nur erhalten, wenn sie als „Schmuckfarbe“ definiert wurde, und hiervon dürfen maximal 27 in einem InDesign-Dokument enthalten sein – und zwar inklusive der Schmuckfarben innerhalb importierter Grafiken.
Example QuarkXPress
Even with the layout behemoth QuarkXPress, which has been known for many years, you can define Lab colours and transfer them correctly to PDF files - similar to InDesign.
Example Scribus
This free layout software is a pioneer in the field of colour, it can correctly handle not only Lab but also HLC colour definitions, read in large colour lists and generate colour sample pages for any number of colours. However, it is unfortunately not possible to correctly pass on Scribus data with Lab colours as a PDF. Similar to CorelDraw, Scribus converts Lab colours to the selected output destination RGB or CMYK when exporting to PDF.
Example AffinityDesigner
Here, too, it is possible to work with Lab colours, but these are lost in the PDF export.
Example VivaDesigner
A Lab colour can be created in this layout programme, but it becomes CMYK during the PDF export, although the PDF format would also support Lab colours in the variants PDF/X-3 and PDF/X-4. This is especially problematic for colour tones that lie outside the gamut of the set CMYK working colour space, because these are displayed incorrectly in the PDF in terms of values and representation.
Conclusion: clear YES
Although it is possible to work with output-neutral colours in the most popular media design programmes, only Adobe InDesign and (via a diversion) Illustrator and QuarkXPress are able to transfer Lab colours into a PDF.
It is completely impossible, for example, to transfer a company logo drawn with CorelDraw in Lab to the layout of the company brochure - no matter in which layout programme the brochure is created. CorelDraw does not offer a suitable file export for Lab colours. It does work in the combination of Illustrator and InDesign, but only if the PDF file contains a maximum of 27 different Lab spot colours at the end - with several external graphics, e.g. in a brochure, this is clearly too few, and some RIPs are limited to an even smaller number of spot colours.
Device-neutral lab workflow across several programmes is hardly possible in the usual combination of bitmap, vector and layout data. There is a need for action on the part of software manufacturers, especially in the area of file formats for vector data and the number of spot colours.
What now?
Solange die Lab-Lösung nicht vernünftig funktioniert, sollte man seine Daten „neutral“ in RGB anlegen. Hier bietet sich der sRGB-Farbraum aufgrund seiner universellen Verbreitung als Quasi-Standard an. (s)RGB-Daten können relativ problemlos als PDF, Bitmap und Vektor ausgetauscht werden, und die CMYK-Konvertierung für bestimmte Druckverfahren ist eine vielfach geübte und funktionierende Praxis. Dies ist jedenfalls sinnvoller, als für jede CMYK-Ausgabevariante separate Dateien im Ursprungsprogramm anzulegen, was vielfach noch immer gängige Praxis ist.
The disadvantage of the RGB method is that, firstly, RGB is not an output-neutral definition (i.e. it must always be stated which RGB it is) and, secondly, that the RGB model is not defined in a perceptually appropriate way and therefore does not function in a perceptually appropriate way. This means, for example, that questions about intermediate colours, counter-colours or colour gradations cannot be answered without further ado. Thirdly, the RGB colour space is limited, e.g. the widely used sRGB cannot represent many cyan and turquoise tones that are possible in four-colour printing.
Author: Holger Everding, Screenshots/Consulting: Eric Soder, Peter Jäger