Hey, guys.
I'm creating poster PDFs for a client in Illustrator.
The photos he's providing are very different in style and their source.
I've come up with an idea to create a transparent gradient rectangle (like a little filter) with a blending mode (hard light) and put it on all the photos to make them visually more consistent and on-brand.

Problem is, I'm not sure what is the best way to get high quality print results.
Should I just keep the rectangles on top of the photos in Illustrator and export as PDF as I usually do?
Should I put the rectangles/filters on the photos in photoshop and export them as pngs or even cmyk tiffs for use in illustrator?
If tiffs - what settings? I'm in EU, tho I should probably ask the print shop at this point?

Forgot to mention, the gradient is made of 4 points of color. I'm not on my computer right now so can't post excact info about the gradient rectangle.

But it's colorful, transparent (20-40% transparency) and has a blending/transparency mode - I think hard light, but might be something else too.

That overlay is a common technique to keep images consistant. If you use a filter in photoshop just set the mode to cmyk to get an accurate preview.

when in doubt (and with vectors + transparencies + old print shop tech) flatten and export as 300dpi jpegs or tiffs. and yeah, check it in cmyk (change your illustrator color space to cmyk and it'll dull the colours to try and simulate the change).

You can do it all in illustrator with artboards and export the artboards. But personally I also worry about banding in the printing gradients, so I add some noise to it. Usually in photoshop where I have more control.

If you're going full autism, best build might be a PSD asset or PNG you've made at 100% physical height + 300dpi in Photoshop. Place that in a layer in illustrator. Put artwork underneath.

Once you do it that way you don't even have to use illustrator really. You can automate with Photoshop actions, or do a data merge in inDesign to crank out 100s of those puppies.

The big thing I would want to avoid is vector + funky blend mode layer shennanigans.

>>460602
Thank you so much for the detailed answer, kind anon.