The final effect – printed materials – depends on both the capabilities of the printing house and the quality of the prepared materials. Appropriate formats of properly exported files as well as correct preparation of these materials are essential to guarantee that colours and typesetting of the materials will meet our expectations.
File formats for exposure
One of the recommended file formats for printing is PDF. It allows to preserve high quality of the materials and to save vector graphics. This is important in printing images of different sizes. In addition, the quality of the file does not change when it is exported to a PDF format from graphic design software. Files prepared in other formats, such as TIF or popular JPG, are not as versatile and safe. Interference with the size of the printed material may result in lower quality of the images.
Unseparated composite files
Before submitting a file for printing a suitable colour space should be selected. This will have a significant impact on the quality and final effect of the print. For CTP exposure only composite (unseparated) files should be sent. This means that individual CMYK colours should not be separated. Files with a visible range of colours used in the material should not be sent. It is not possible to guarantee the quality of colours in the case of RGB, customer profiles, etc.
Every material printed in colour is created using the 4 basic printing colours (CMYK). Before sending a file to print, the colour space should be changed from RGB to CMYK. If other paints are to be used in the printing process, colours from Pantone palette can be chosen. Another acceptable option is greyscale.
It is worth remembering that if colours of RGB, LAB or Indexed Color types were used, the colours after printing from CTP matrices may appear different than intended by the designer.
Black text overprint
Black texts must have the overprint mode set. They should also be made of one component 100%K without the use of the other three CMY colours.
All works on CTP must be centred and have bleeds of minimum 3 mm.
Pages may not include bleeds only when the background is white. Graphic elements and texts should be moved away from the edge of the net format by at least 3 mm. Such bleeds are a reserve for the designed graphics which exceeds the cutting line of a flyer, business card, poster, etc. They are cut en masse using the guillotine whose pressure can move the cutting line. Bleeds will prevent the creation of unsightly edges.
We advise against locating important elements, such as photos, texts or logos close to bleeding as it has an adverse effect on the aesthetics.
All pages of the works need to be centered. In case of inserting page design on target materials, it is worth remembering about accurate centering in order to avoid uneven margins.
Pages intended for imposition
In multi-page printouts, when the order includes imposition with assembly from individual pages, centrefolds also need to be cut. For example, in a publication where the assembly is in the A4 format, spreads cannot be uploaded in the A3 format.
Formats of the pages intended for imposition
All page formats in one assembly need to be of the same size. An exception to this rule is the cover with glued binding – it should be prepared as a centrefold including spine.
Markers, printing registrations, etc.
It is best to prepare pages for imposition on CTP without printing registrations, wedges, densitometric scales. Only set-aside cutting lines (symmetrical bleeds of minimum 3 mm) are acceptable. Bleeds are not required only in the cases where the background is white. Cutting lines should not interfere with bleeding – distance from bleeding should be maintained.
Resolution, overprint and coverage
Minimum resolution of the photos in the file should be 300 dpi. Using resolution other than this may result in pixels being visible in the printout. The exception includes materials printed in large formats where resolution can amount to 200 dpi.
Black texts need to be overprinted (overprint option must be turned on).
Maximum coverage of an area should not exceed 300%. Even lower percentages are usually enough – depending on the type of the printed paper or other material. Inappropriate matching of the area coverage may result in spilling the paint over the material.