I am preparing digital photos for printing and performing various test prints for comparison (with a very cooperative print shop). The print shop only accepts PDF, not direct print from raster format PNG etc. The can handle up to 1200dpi on sizes up to A3, and 1440dpi for A2 and larger (on a separate machine).
My sources are iPhone X photos (super for a mobile phone) and Sony A7Riii photos (42M, utterly stunning).
I am aware that comparing digital images on a display (in my case a 5K iMac) and printed versions is a bit like comparing apples and oranges. That notwithstanding, I am so far disappointed with the printed results from PDF prepared in all of the following tools:
Mac Pages 7.0 (which seems to pass through Mac OS X 10.13.3 Quartz PDFContext)
Pixelmator Pro 1.0.9 (which likewise seems to pass through Mac OS X Quartz)
Photoshop CC (very latest 19.1.3), using Save As to Photoshop PDF.
InDesign CC (very latest), using Export As PDF.
In all cases the PDF versions, from which the print is made, seem to "smooth" out the original image, resulting in a clear drop in sharpness, at least as far as I can tell comparing display views of the PNG with prints.
For example, in the image below, I have a screenshot from a 5K iMac display of:
Left: The Mac Preview view of a PNG. Note the pixelated anti-aliasing around the blue and red spots, which from a distance lends a certain "sharpness". Image (as cropped) is 3835 x 2490.
Middle: Mac Pages PDF export, an A3 layout with 5mm margin, with the image scaled to fit inside the remaining horizontal 410mm (pls ignore vertical part). Mac Pages does not AFAICT offer any explicit control over DPI on document creation or export to PDF (unless it is hidden somewhere). Note how the blue and red spots appear smoothed; on printing, the result is a loss of sharpness (at least as I perceive it).
Right: Photoshop CC: A4 document created at 600dpi, so for no scaling of the inserted image, it takes up 162.35 mm x 105.41 mm. Document processed as RGB (until export). For the sake of this discussion it seems to make no difference, to the "sharpness", whether export to an RGB profile or a CMYK U.S. Web Coated SWOP (except for colour as seen on a display of course). On export I ensure the images are handled as LOSSLESS (no compression, and no ZIP or JPEG etc.), and with Do Not Downsample.
(I have omitted the result with InDesign CC, with direct insertion of the PNG into a layout document and similar PDF export controls, including 600dpi and 1200dpi throughout. Result is same as Photoshop CC.)
Q1: What am I seeing ? Why don't the images simply propagate through the pipeline otherwise unaffected ?
Q2: How can I ensure the best print reproduction that somehow corresponds to what I am seeing on digital displays (including my iMac, iPhone, and Sony camera displays, all of which are showing higher clarity and sharpness) ?
And for reference: I am using Exiftool to examine metadata. It yields expected DPI indications in the final PDF for Photoshop CC and for InDesign CC such as, for 600dpi pipeline:
X Resolution : 600 Displayed Units X : inches Y Resolution : 600 Displayed Units Y : inches
But for Mac Pages and Pixelmator Pro, which have no clear PDF export controls, a typical exiftool probe reveals no such indications:
ExifTool Version Number : 10.80 File Name : IMG_XYZ.pdf Directory : . File Size : 2.4 MB File Modification Date/Time : 2018:04:08 13:41:54+10:00 File Access Date/Time : 2018:04:08 13:42:29+10:00 File Inode Change Date/Time : 2018:04:08 13:42:01+10:00 File Permissions : rw-r--r-- File Type : PDF File Type Extension : pdf MIME Type : application/pdf PDF Version : 1.3 Linearized : No Page Count : 1 Producer : Mac OS X 10.13.4 Quartz PDFContext Create Date : 2018:04:08 03:41:54Z Modify Date : 2018:04:08 03:41:54Z