Common Prepress Problems & Solutions
Problem: Artwork supplied as RGB or Indexed colour
Solution: All artwork must be supplied in CMYK or if required Pantone PMS. It is relatively easy to convert your RGB file to CMYK however some of the colours will change. The reason for this is that RGB has a slightly different colour gamut to CMYK – some of the colours do not have a direct equivalent in CMYK and visa-versa. This means that the conversion software has to put it in the closest alternative colour available which of course can suitably change the look of your printing. Whilst this is not a problem for most people it is always best to create your design in the colours it will be printed in.
Problem: Low resolution images
Solution: When designing digital files intended for professional printing, it is essential that all of the photographs and images in your in files are high resolution. If you have ever seen printed material that contains blurry or blocky images which often provides a bad presentation, it was likely caused by incorporating low resolution images. Ensuring a high quality printed job is as simple as making sure all photos and images in your digital files are all high resolution.
Problem: No bleed or enough graphic to make bleed
Solution: If you want your print to be full bleed (edge to edge) you need to include an extra border of colour that will be cut off. Remember that you need to include crop marks as well.
Problem: Artwork too close to the trim edge
Solution: Adding a trim allowance of at least 2mm is important as it serves as a margin for cutting differences in producttion. Paper is a natural material which is subject to fluctutaions caused by environmental influences such as temperature and humidity. Therefore there can be discrepancies of up to 1mm for the final cutting. These cutting differences can also affect the creases of folded products. Important information and text elements must be positioned at least 4mm away from the final format edge. For saddle-stitched and bound documents we recommend placement at no less than 5mm from the edge, especially for brochures with a high number of pages.
Problem: Missing fonts
Solution: All fonts should be converted to curves. If this is not possible, the fonts must be completely embedded (not just as a subgroup. When converting to curves, please ensure that the space character is correctly converted.
Problem: Lines too thin and don’t appear when printed
Solution: Don’t make your lines too fine especially if there is a complicated background as they will not show up when printed.
Problem: Inconsistent rich black values
Solution: For measuring the tonal values and differences, switch the information palette to SMYK and a 32-bit mode. Black can simply be c:0 m:0 y:0 k:100 or for a nice rich black when printing in colour you may like to use c:50 m:40 y:40 k:100.
Problem: Overprinting used incorrectly
Solution: If your artwork has two different colours superimposed, there are two possibilities. The foreground colour chokes the background colour, or it ‘overprints’. Overprinting means that all the separation colours not used in the foreground colours are transparent, and the background filters through in these areas. For example, a red, defined as overprint (comprised of yellow and magenta) is transparent in the colour separations cyan and black. The cyan or black contents of the background colour are then printed, so that the result is a mixture of background and foreground. Colours incorrectly defined as overprint, rather than choke, are a common error because the resulting mixtures of foreground and background colours are often not displayed on the monitor and also are not visible on all printers. In general we do not check overprint settings as they may represent a design idea.
Problem: Screened percentages for colours higher than required because of dot gain
Solution: Dot gain is a phenomenon that causes printed material to look darker than intended. This happens because the diameter of halftone dots increases during the prepress and printing process. The optical and physical properties of the media and machines used both in preparing the job for print and the printing process itself cause this behavior. Prepress and press operators can try to minimize certain types of dot gain but cannot avoid that dot gain occurs. As such it is also the responsibility of the designer to be aware of dot gain and to anticipate its effect. You typically find dot gain controls in applications like Adobe Photoshop.