(Amazon KDP) Vectors in PDF/X-1a:2001 printing more black than PNGs, but display identical digitally

Question

Hello!

Perhaps someone can help me. I am preparing a black and white paperback manuscript for printing through Amazon KDP's print on demand service.

From InDesign I export a PDF/X-1a:2001 (per Amazon KDP rec) which contains solid black PNGs. These PNGs are, for example, a logo with a transparent background, or solid black silhouettes with transparent backgrounds. (Transparency I figure isn't relevant here considering it gets rasterized away by the PDF/X-1a standard.)

These solid black images print with what appears to be some sort of grey; the ink itself is not grey, but is perforated with the tiniest white spaces, and appears to be 'sprayed' onto the page in a different manner than how everything else in the manuscript gets printed, as it's got these rather rough lines which don't seem to be the product of pixelation but rather due to the manner in which the ink gets onto the page, which I assume has been determined by the interpretation that the printer has made of the rasterized pixel data in the PDF.

Everything else in the manuscript is also solid black, but prints smooth. Everything that prints smooth is incidentally vectorized, being either actual text or outlined text.

So: the rasterized, solid black content (logos and silhouettes) is printing different than the vectorized, solid black content (text and text outlines).

I've attached an image. On the left is how it appears in the PDF, and on the right is how it appears printed. The rounded box of text in the lower right hand corner is actually an image, a silhouetted PNG. Notice how it prints differently than the vectorized content of the text above it, despite appearing indentical in its blackness in the PDF. (If you zoom in you can see the 'perforation' that I'm talking about--it's not a solid black, unlike the vector content above it.)

The export settings which produced this print are:

PDF/X-1a:2001
Acrobat 4 (PDF 1.3)
All three Compression drop-downs set to Do Not Downsample
Compression for Color, Greyscale and Monochrome set to Automatic (JPEG) (maximum), Automatic (JPEG) (maximum) and None, respectively
Compress Text and Line Art is unchecked.

I think that I can achieve the result of the rasterized black images printing smooth if I can vectorize them. I don't know how to get the images into the PDF/X-1a standard and retain their vectorization. SVGs that I drag into indesign turn into rasterized images when exported, this way.

Could I, for example, 'outline' the images in the same way that text is outlined to produced vectorized pixels resembling text? That I think would be an effective workaround, if possible.

Or if there's another way--I'm ALL ears!

Thank you for any help!!!

rob day · Accepted Answer

If you zoom in you can see the 'perforation' that I'm talking about--it's not a solid black, unlike the vector content above it.) What you are describing and showing in your capture are halftone dots. The placed PNG has to be RGB, and an RGB black would always convert to a 4-color black with a PDF/X-1a export. Looks like KDP prints the page as black only, so the halftone is showing on the edge because of the conversion from 4-color CMYK to 1-color black (grayscale) at output. A possible solution would be to open the PNGs in Photoshop, make sure the black is absolute black (0|0|0 RGB), convert to grayscale, and save as PSD. When you place the PSDs, use InDesign’s Separation Preview to confirm that the rasterized text is reading as 0|0|0|100 CMYK

James Gifford—NitroPress · Answer

Looks as if you've gotten good answers, but I will add a point: PNG is best for web/electronic display and should be avoided for print no matter how many layers (such as PDF) it passes through.

Use JPEG optimized for print for more consistent, reliable images. Best is to convert to grayscale before placing; PDF export using a grayscale profile works almost as well.

Or, best of all for illustrations involving text, try to keep the text live/vector instead of part of a rasterized image. Lay the text in as ID text boxes, or create and export PDFs from ID, Illustrator, etc.

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