saving to PDF Files are down Sampling raster images for large format printing

[jimj67429185]

I am the Art Director for a large format printing company. We save our files out of Illustrator in PDF format to send to our RIP stations. For some reason in the past month, randomly, files are saving with raster images as very low res images. Most files are vector, and those areas are just fine. But sometimes the raster images that are in the files are saved very low res. I have checked that "DO Not Downsample" is checked. I can save a file and it is perfect, save it again and it is Low res. I am on the most current versions on Adobe. Has anyone else had any simular issues? It is cosing a lot of trouble and reprints. 

[Bobby Henderson]

Which Adobe PDF preset is being used? For large format printing I typically use the Illustrator Default, which doesn't down-sample or lossy compress any raster-based images. If other presets such as "Smallest File Size" get selected the PDFs will be saved with raster-based objects down-sampled and aggressively lossy compressed.

[jimj67429185]

We have been using the default preset. When this started happening, I made a preset for high Quality and made sure no downsampling was chosesen. I thought it was working, but have had 4 files mess up in the last two days. One file I saved and it was fine, I had to resave for another reason and it saved low res. 

[Bobby Henderson]

Other than someone making changes in the PDF export settings I'm not sure what else could cause the application to down-sample the images when saving the PDFs. Are all the images embedded in the Illustrator document before saving the PDF? I'm not sure how it could affect things, but are the PDF files being saved across a network share or saved on the local hard disc in the computer?

[jimj67429185]

It is definatley a strange issue. Most of the images are linked to the high res file on our server. they are generally the same files. the randomness is the real kicker as the image file is never changed. yet most times it save just fine, then all of the sudden, its low res. the file sizes are also very small. We are trying to look for this to check before it prints. We usually do not embed these, just use the linked files. We do work on servers, the files are saved from a server to a server. Not sure if there is an issue w the server corupting some files? Been very frustrating.

[Bobby Henderson]

I typically embed the image files in PDFs I generate for large format printing. The file sizes can be huge, but the PDF loaded into the print queue is ultimately a temporary file that gets deleted.

In the past it was common for EPS files to include low resolution "preview" images for file browsing. I'm wondering if somehow the same sort of thing is being generated for these PDFs. Somehow the link to the high quality file gets broken and the low res preview image get used instead. Normally I would just see an error about a broken link when opening a PDF with image link errors.

If your large format RIP software doesn't automatically download and install updates it would be a good idea to check and see if any updates are available.

[jimj67429185]

The Print/RIP side is checking for updates. But it looks like the issue is before the RIP. The files are saving very small when it does mess up. And. It doesnt matter if images are linked or embeded. The files w issues have both types of images. It seams to effect all images when it does this. 

[Bobby Henderson]

Since the files are being saved across a network I wonder if there is some kind of permissions issue. Usually in those cases an attempt to save a PDF on another computer would be blocked or remote access to files would be blocked. Still, it's pretty strange a high res image file would fail to remain embedded in a PDF when the file is saved.