I understand that you may know what the technical aspects were, but my experience on other forums is that other people may not understand.
I tend to start at the bottom and be explanatory and basic as possible, then when necessary I can ramp up the talk depending on how the topic flows.
I fully agree, some printers do not simply adopt modern workflows, choosing EPS over PDF and flattened TIFFs over layered PSDs (or layered tiffs).
Some are simply computer jockeys, taught to ride the horse but never question the trainer. Some simply use a "preflight" that was handed down from the mid 1990's to generation and generation - never being updated.
Some ask for all CMYK document or they won't output.
Recently I had a spec saying "PDFs created on a Mac are only accepted" and my upper management team panicked and wanted to buy in £20,000 worth of Mac equipment!
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But keeping things in their respective profiles while you work will benefit you also.
Think if your publication needs to go to an eBook - or an online PDF - or HTML5
You're going to need to keep your images in the widest gamut available.
so keep them in their native gamut when you are working with them.
The up side to a PDF workflow is you can choose your Destination Profile when outputting the PDF. This won't be a PDFx4a compliant file - but it won't need to be.
You can still output your PDFs to various destinations, like Coated Fogra 27, or 39, Uncoated, Newsprint, Euroscale or whatever.
And you still get a fully CMYK PDF.
The key there is not to include the Profile with the PDF - otherwise what happens is that when they open it their end the profile will be mapped to whatever junk they have there that isn't what you want.
A pdf with a Convert to Destination (Preserve Numbers) works fine for me most time going to Coated Fogra 39 (as I mostly output for coated stock).
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I think it would be worth your while to find a company that is PDFx4a compliant.
You can arrange proofs with them until satisfied you have a workflow.
In the end you benefit greatly with this workflow.
And the dinosaurs are left in the dark ages, where they belong.
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Sorry if I went off track there - but hope that cleared up somethings.
Like you don't need to be PDFx4a compliant to send to all your printers.
You can still send PDFx1a to printers, flatten eveything and convert everything to a destination profile - it will probably be fine.
I always always always get a colour proof that has gone through their RIP. I make sure to make that time a must in the print schedule.
Even if it means me taking a trip to the printers to proof on machine.