RGB or CMYK images in documents for print?
Written by Lasse Krogell, NOPA
In addition to my print business consulting, I also run a fine art photography print service. I just finalized a photo exhibition with 40 beautiful color works for a customer. My customer also published a photo book from the same material. She told me that the first proofs she got from the book printer were extremely disappointing. All the photographs in the pdf sent to the printer were converted from rgb to cmyk. It turned out that the profile used for the conversion was not the right one.
This gave me the idea to write this article. At least in Finland, most of the offset printers still demand the customer to send the material in cmyk and not in rgb. When I have raised this question with printers in Finland, they usually say they think it is best that the the customer and not the printer should be responsible. Almost 20 years ago when I worked for a heatset printer in Finland, we got a magazine print order from Sweden and the customer demanded that all materials should be sent in rgb and that it is the responsibility of the printer to convert to cmyk according to their processes and profiles. Today this is common practice in Sweden. I did some googling and noticed that in the “NOPA region” it is common that the instructions recommend cmyk. In most cases the recommended conversion profiles are listed.
The comprehensive document, “Media Standard Print 2018”, technical guidelines for data, proof and production run printing, published by Bundesverband Druck und Medien, is perhaps the best data source in our region for print production. In Table 2A “Colour data and preferred file formats” both rgb and cmyk are listed. In Table 7 “Typical applications for digital printing methods” cmyk is mentioned only for application: Variable Data Printing. In all other applications the recommendation is rgb. As we know, today often the printer wants to be able to decide if a job should be printed in offset or digitally. Taking this into account the rgb format is the preferred one also according to this referred document.
In modern pre-press workflow systems, the rgb to cmyk conversion can be automated. There is not anymore, any real reason why a printer should ask the customer to send cmyk data to the printer. But there are several reasons why the rgb format has its advantages. For example, in advertising the same material can be used for ads in different magazines printed in different processes. Materials for a magazine often comes in from different sources. Wouldn’t it be best that all materials are process independently and that the process specific conversions are made by the printer, that must have the best knowledge about the printing process and the materials used? Furthermore, the file sizes in rgb are smaller.
In some colour critical cases the customer is concerned how the images will reproduce in print. For this the profile that will be used can be uploaded on the customers computer and the material can be soft proofed and possibly edited to optimize the colour rendition.