Exporting Scaled Down Artwork to PDF for Large Scale Print

Question

I've been a graphic designer working mostly in print for the past 15 years and I just realised that the way I have been exporting for Large Scale Print has been wrong this whole time.

Normally if there is something that is a few metres I might create the artwork at say 10 or 50% keeping things like bleed to scale. I make sure images will be at least 150dpi when scaled up so if it's 10% I will make sure the images are 1500dpi.

However most print PDF defaults compress any images over 300dpi down to 300dpi. I only just realised that all those scaled images I've been setting up have been scaled down again.

I've never had a printer come back to me saying there was an issue. For anyone working in print production, would you just run it as is because it's not usually a problem or are there no preflight systems that pick this up?

Answer 1

I am paranoid :o) so I would use the correct terms in the first place, this is one of those things that will make you a better print production guy.

most print PDF defaults compress any images over 300dpi down to 300dpi

No, they are not compressed, they are resampled, and this is a checkbox that can be easily deactivated.

DPI

The unit you should use is PPI, regardless that they are commonly used as the same unit they are not.

I make sure images will be at least 150dpi

150 PPI as a final resolution is probably too much. 100 PPI is a good resolution that will not be visible on an image at 1 m.

The images you export at 10% at 300PPI have a final resolution of 30 PPI, which is in fact still a decent resolution. It is a small square of less than 1 mm when viewed at a couple of meters is again unnoticeable. As long as the text remain as a vector, this is still a good file.

Regarding your question

For anyone working in print production, would you just run it as is because it's not usually a problem

I am not in that part of the chain of print production, but in any case, that specific issue is no obstacle to print it as it is. I mentioned it early 30PPI is a good resolution for a few meters print. There is no way to know you intended a greater resolution but did not unchecked the resample box.

An example of a warning that should not be allowed to continue without double-checking is, for example, a small black text in RGB colors. That kind of warning should be stoped and called upon.

are there no preflight systems that pick this up?

Probably you can setup a warning if a file has less PPI on a file than some amount, but 300PPI is a standard good resolution so, there is nothing to warn about.