The question often arises whether color profiles should be embedded in the PDF files for proofing.
To answer the question, you have to get some answers: The proof should simulate the subsequent offset printing. For offset printing, with few exceptions, the imagesetters have been configured so that a 70% black in the file is displayed as 70% black on the printing plate, no matter what profile was specified in the file. It didn’t matter whether it was coated paper or uncoated paper: 70% in the file corresponded to 70% on the plate, the choice of the paper printed on resulted in the colour representation.
The proof has also adapted to this: Most proofing service providers ignore embedded profiles, as long as the data is in CMYK and do the same as their print colleagues. Even with grayscale, the profiles are usually ignored and the grayscale is simply assigned to the CMYK black channel. Thus all CMYK and grayscale data are simply interpreted as if they had been created in the output color space. If “ISOCoated V2” is proofed, all images are treated as such, and if “PSOUncoated” is proofed, then the CMYK images are created in this color space.
This is excellent for the majority of files to be proofed. Only RGB colors contained in the data are problematic.
Since the RGB color space is considerably larger than most CMYK color spaces, it must be clear from which color space to convert to CMYK according to which criteria. Most proofing service providers specify a color space from which they convert by default if no RGB color space is defined. This can lead to difficulties: For example, many proof studios choose AdobeRGB as color space because it is large and optimized for offset printing; however, most images from digital cameras come from sRGB and these color spaces differ considerably. Therefore, it is important that the RGB color space and the rendering intend is embedded for a proof, otherwise the proofing software normally selects a color space for conversion to the CMYK color space to be proofed; and this color space is possibly not the one in which the data has be created.
The background to this is that especially the big german discounters like Aldi, Lidl, Hofer & Co. want to see a packaging proof from their suppliers in advance for approval. This packaging proof is not only visually assessed according to colour, but also the legibility of the printed EAN codes is evaluated using a measuring device and must meet certain criteria: Symbol contrast, modulation, decodability, defects, blemish: all this is measured and graded.
This involves two different risks for the advertising agency or the reproduction company that processes this data: Firstly – according to our information – in most cases the proofs are not viewed under D50 standard light, but under TL84 – the light under which the packaging will also be seen in the later sales situation. This is understandable, since the sales process takes place under TL84 and not under the standard light of a printer. On the other hand, retouching under TL84 is not mandatory, since the spectral behavior of “standard” neon means that it is not possible to produce such a reproducible and “color-accurate” result as under D50. In addition, a colour matching box with D50 and TL84 is available in very few companies, which makes it possible to view the result under both light conditions in the colour retouching.
Secondly, the proofed GTIN barcodes are measured by a measuring device and checked for their mechanical legibility. Whereas a few years ago a press proof was the standard for such tests, today mostly the digital proof is used, since it is much cheaper. But until now, the manufacturers of proofing software have always only paid attention to the representation of color, but never to the verifiability of black and white lines.
Especially with Fiery proofs, but also with GMG Color, the lines of the GTIN barcodes are usually reproduced in such a way that they correspond exactly to the black value of the required profile in terms of color, but only school grades of 3 or even 4 are achieved during the examination, depending on the discipline. Most scanner cash registers could still read and process these barcodes without problems. However, ALDI Süd or Hofer with their own GTIN codes require at least a second grade in all disciplines: The proofs all fall through the test grid of the discounters. In particular, the decodability of EAN codes has probably not been of particular importance to proof manufacturers up to now.
After detailed tests, the width increases of the GTIN bars in the digital proof and the blurring of these bars seem to be the biggest problem for the verifiability of the codes. Farbproofs.de has developed a solution together with one of the testing companies for barcodes that makes it possible to print testable GTIN codes in accordance with the strict ALDI standards, which also comply with the current proofing standards. A proof is therefore sufficient for colour matching and for checking the GTIN numbers. However, the EAN must be created and edited specifically for this purpose. This still costs far less than a conventional proof, but it is not satisfactory. Manufacturers of proofing software such as EFI and GMG Color are therefore called upon to improve the calculation of black and white line representations in writing and GTIN codes.
Until now, the focus has always been on color accuracy, but the proof increasingly demands services that were previously reserved for proofing. At costs of 5-10 EURO for a digital proof in DIN A4 format and 150-300 EURO for a proof in the same format this is more than understandable.
An article with tips for the creation of EAN / GTIN codes for graphic designers and the problems of verifiability of EAN and GTIN codes for e.g. Aldi, Hofer, Lidl and Co can be found here.