I'm working with an online "print on demand" printer and the subject of "unnecessarily high resolution images" has come up. I have, in the past, for offset print production, used "900-1200 ppi" as my resolution for bitmap images placed at (on or around) 100% in InDesign. I was told to res-down these images to 600ppi in Photoshop, link them in InDesign, and then apply the PDF/X:1a2001 on export. I was told recently, to only alter the bleed settings, but had changed one setting, see below. Changed monochrome to 600 ppi max. Could that have any effect if my images were already placed at, or close to 600ppi? It was suggested, after the files were submitted, that I retain the 900ppi down sample for images above 900, and not change to 600 on export:
I'm just curious. Will that degrade images further somehow? Or is it of little concern?
One other question, after the fact. My project was a 210 page document heavy with imagery. I worked in several InDesign files, exported to PDF/X:1a2001, creating several PDFs, and then joined them together into one file in Acrobat. Is there any reason not to work that way? The files were so large, in InDesign, that I didn't want the possiblity of corruption to "take out" the whole file. I've learned to work in sections. Thank you for any light on this subject.