In printing, registration black is a black colour that includes 100% of each of the process colours used. Typically, these are cyan, magenta, yellow and black (CMYK), but if different colours are used, registration black marks are made with all the colourants (inks).
Registration black is used for printer marks, aka registration marks. When proofs for each colour are generated on separate pieces of film, the use of registration black makes crop marks visible on all channels, providing a useful reference for alignment. A thin line printed in registration black can also be used to check whether the printing plates are aligned. However, this should never be used in the live area and only for printer marks.
Any issues with registration colour are flagged in the pre-flight report as the following errors:
- Registration Color Inside BleedBox (>0%)
- Registration Color Inside TrimBox
How to fix this Error
This error will refer to two issues:
If your ad has crop marks, they may be bleeding onto the page area
If your ad does not have crop marks, there is a registration colour within the page area that the publisher does not allow
To fix this issue, perform the following:
For (1), please ensure that your crop mark offset is set to 5mm when you export if your ad requires crop marks.
For (2), if your ad does not have crop marks, please ensure that the swatch you use for black colours is called Black rather than Registration.
There may be an occasion where both of the above are applicable - crop marks bleeding onto the page area and registration colour used within the page area. If this is the case, please follow both steps above.