In experimenting with various PDF presets, I noticed that with grayscale images in Photoshop, saving as PDFs using different presets, alters image quality, specifically the contrast.
Therefore, it seems like saving an image in the "wrong" PDF preset could undo a lot of prepress work. Is there a better way/format?
To get a crude idea: there is an 8.7% decrease in the percent black between 10% and 50% values (the range) on a step wedge between the original in Photoshop and the HighQuality PDF, which showed the same values, and the PDF/X-1a, which compressed the range by 4 percentage points (approximately a 8.7% decrease).
A visual, and idiosyncratic, assessment of four versions of the same image (Photoshop grayscale, High Qualtiy PDF, PDF/X-1a, and PDF/X-3), which included a step wedge and color ramp, would rank the fidelity to the original from best, HighQuality, to worst, PDF/X-1a.
The same grayscale image in Photoshop CS6 was distilled (File > Print > Adobe PDF) to PDFs using unmodified PDF presets in Acrobat XI distiller.
The following composit screen shot (all four images on the screen, screen print, reorganizing them, then reducing the image to a 120 dpi at 4.2" wide (including text) gives some idea of the differences, but a lot got lost getting it here.
Walton