Recently, my client came back to me with this: https://imgur.com/a/NWI3wll. They've told me that the InDesign file that I gave to the printers is not high in resolution enough that caused this.
However, from what I see from the images they sent me, it looks like matte lamination is the one that caused this. To make sure, I went back to my INDD and check all images to ensure they are 300ppi and above. And yes, all is well and in place.
What could be the cause?
Unless you post the PDF file (or at least part of the PDF file) you provided to your printers, it is impossible to determine what is really going on.
Of course, providing an InDesign file (and assets) to a printer is not best practice. Providing a press-ready PDF file is a much better workflow, preferably exported from InDesign as PDF/X-4 with live transparency and ICC color management.
Yes, it's rare for printers to requests your working files. Press-ready PDFs are what I usually provide. However, this is an exception since the printers insist to print it via the working files. I'm not sure what are the settings they saved in or how they print it either (from PDF or directly from INDD?). Everything is pretty puzzling at this point.
I'm hoping to talk to the printers myself actually but am still trying to acquire their number from my client.
When you state the images are 300PPI, can you confirm the Effective PPI of the images are 300PPI or simliar?
Yes, effective PPI is higher than actual. This is something that I will always make sure of.
You have lots of fine lines in your graphic. Even if your original was quite high dpi originally, having it downsampled to 300 when making a PDF can make them a bit fuzzy. 300 is great for photo images, but it's not enough for small type and fine lines. (This is the kind of thing that should have been vector, but if all you have is bitmap images, let's see what can be done). I suggest you/your Printer create a PDF where the settings for Sampling/Compression settings are set to Do Not Downsample and Compression to Maximum. Further, there's a chance that your Printer's RIP system downsamples it as part of their workflow, in which case, they are introducing the fuzziness there, too.
This doesn't look very much like an resolution issue, the lines look pretty sharp to me (or at least not pixelated or something).
This DOES look like you've set, some sort of lamination/protective foil or the paper itself reacts this way to ink.
Without having the print in hand I can't say for sure of course, but I would bet on it 😉
So I don't think there's anything wrong with your data.
Afterthought: it could be the resolution of the printer but again not your data.
I've seen this kind of quality also in digital printing, but more in the LFP (Large format printing) world.