When there are 2 or more colors to make sure no element has been accidentally dropped, and that the different color elements are in proper registration. Similarly, if you submit a job with loose pictures and we have to scan or shoot these. Also when we have to strip in several halftones or pieces of line art, blue lines will show whether an element was left out or put in a wrong position. What a publisher should try not to use blues for is a final proofing of the publication. To make changes at this point not only inordinately delays production, but costs considerably more per correction because the new art has to be expressed, processed and redone.
Blue lines run the gamut from unnecessary to indispensable.
Like any other tool, they work best when used for the right job. Copyright 1994 Marrakech Inc . All rights reserved.