When preparing print files, keep the following in mind:
If any objects in the layout touch the edge of the page, you must add a bleed of at least 3 millimeters (some processes require a larger bleed, we will inform you in that case). Any images, backgrounds, or other objects that touch the edge must be continued into the bleed area. This is necessary because the final trim can vary slightly throughout the run.
The resolution of images should be between 200–300 dpi. The optimal resolution is double the lpi (lines per inch) used in the printing process. For a magazine printed on coated paper, lpi is 150 and dpi is therefore 300; on newsprint lpi is 85 so dpi is 170. Note that simply increasing the resolution of a low-resolution original can’t restore lost details. Layout software can show you the effective dpi of your images.
For normal, four-color printing make sure that all images and objects are in the CMYK color space. In most cases, text should be set as black (K). Only use spot colors (Pantone) if you intend for it to be printed as an extra spot color – spot-to-CMYK conversion will often result in significantly different results due to the limited color gamut of CMYK. Also keep in mind that we can match spot colors to Pantone booklets only on untreated paper – any further surface treatment like varnishing or lamination can change the optical properties of the page and change the tone.
Photography and displays use the additive RGB color model. RGB has a much bigger color gamut than the subtractive CMYK model. One-to-one conversion isn’t possible – each RGB tone has to be translated to a visually similar CMYK equivalent. The “recipe” for this is called an ICC profile. Different papers and processes require different recipes, which is why it’s important to use the correct ICC profile for the paper you’ve chosen. We recommend keeping images in RGB in your layout file (but work in CMYK preview mode). Convert only when you export the final print PDF. This way you can change profiles without having to manually re-convert all images. Applying a profile to any image that is already in CMYK does nothing. ICC profiles can be downloaded here.
A PDF standard is different from an ICC profile. It’s a way to create a compliant PDF file that can be safely read by prepress software and converted to printing plates without data loss. When creating print files, use the pre-defined standards PDF/X1a or PDF/X4. Be sure to use fonts that are licensed for embedding, otherwise you may not be able to create a PDF/X-compatible file. Adjust the preset to use the appropriate ICC profile. We can provide .joboptions files for Adobe CC workflows, if you wish.
Our prepress system sets all 100% black text or vector objects to overprint by default, even if they are not set to overprint in your files (this is to avoid registration alignment issues). Any CMYK colors (including white) with overprint will have the overprint turned off automatically because it’s almost always an accident and will result in disappearing text or other problems.
However, in very complex PDFs the preflight software may not be able to isolate all of these issues and therefore we can’t guarantee it will fix them 100% of the time. That’s why it’s important to avoid these problems before the PDF is even created.
If you want to use deliberate overprint effects with CMYK inks, please inform us beforehand so we can temporarily turn off overprint correction for those pages.
If you want to use a black object that does not overprint, add 1% each of CMY into the color – (1C/1M/1Y/100K).
Solid black colour objects (except text and thin lines)
To avoid “pinholes” from paper dust and dull black color, always use CMYK black (rich black) for larger black objects. There are many different recipes that create blacks of different shades. Our recommendation for a neutral rich black is: 40% Cyan; 30% Magenta; 30% Yellow and 98% Black.
To ensure sharpness, text smaller than 8pt or lines thinner than 2pt should not be a combination of component colors. Use a solid 100% of any component color (100% black, or 100% cyan, etc). At most, use two component colors for objects this small or thin.
To ensure a legible result, we do not recommend white text on a solid background (negative text) that is smaller than 6pt (for sans-serif fonts, e.g. Arial, Helvetica) or 8pt (for serif fonts, e.g. Times New Roman). Likewise, we do not recommend negative lines thinner than 1pt.
All necessary printing marks are added in our prepress process. Please do not include color bars, registration crosses and other such data in your file. Including crop marks is optional but encouraged for easy visual verification of bleeds.
When printing to match optional GMG digital color proofs, we can only achieve reasonable tone matching on untreated paper – just like with spot colors, any further surface treatment like varnishing or lamination can change the optical properties of the page and change the tone. Paper brightness (how much light it reflects) and whiteness (the color temperature of the reflected light) can also limit how closely the proof can match the final printed product.