Are JPG and WEBP Appropriate Image formats for Offset Printing in 2023?

Question

I teach an introductory graphic design course (PS, Illustrator, InDesign) for Media Arts students. I try hard to re-evaluate the material and grading criteria regularly so that I'm focusing on aspects they'll realistically run into doing the work and not just dogmatic repetition. Suffice to say that I have historically spent a lot of time talking to my students about why JPEG and WebP are not appropriate formats for a print production.

I understand the fundamentals here, but realistically is this still a problem? I stopped making a big deal about CMYK vs RGB some years ago because the offset printers I work with for my own work didn't seem to care that much anymore since their RIP output is functionally identical. So is it the same for using a JPEG in your InDesign layout these days? Especially considering they mostly work with stock photography that comes to them as a JPG regardless?

Thanks.

EDIT: When I say "I understand the fundamentals here." what I mean is that I understand the concepts of lossy image compression and generational loss. But when I was coming up and learning desktop publishing principles, JPEGs were considered fundamentally incompatible with offset print production regardless of their compression level (full color JPEGs could come grayscale in production) and a designer submitting a Quark package containing JPEGs would have their work instantly rejected by offset printers for production. So I'm not asking whether JPEG (I confess I just threw WebP in there) is the best choice choice for print production (which is a much bigger conversation with many competing factors), I'm asking if JPEG is still fundamentally incompatible with the offset printing process the way it was a decade ago.

Answer 1

For me, I ditched the myth of "JPG not for print" some decades ago.

If you have control over your process, using the maximum quality, the data degradation is less than 0.5%. Meaning that only some zones of the image will have a change in the value of the pixel of 1, this is 1/255 Probably no one On the planet will visually distinguish that difference. Even in CMYK, we use jumps on values of 1/100!

Here are the tests and methods I used. https://otake.com.mx/Apuntes/PruebasDeCompresion/2-CompresionJpgCalidad.htm (I really need to update that page! and make an English version)

I am working on a comparison of the degradation between JPG and WebP (And AVIF), but again, on the maximum settings, the degradation is imperceptible. Avif and WebP declare that have a lossless mode, (but one of them, according to my limited testing is not. But I do not remember which one is it. It is on another hard drive)

The problem is that if you open the doors of using JPG to "normal people" chaos will erupt. Complaints on final quality over a "downloaded image from the internet" will be all over the place.

As long as you keep a good workflow, and know the limitations of it, you will be fine.

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P.S. Regarding your edition on the question.

You almost do not use "native files" for print production. You generate a PDF, so, the JPG files are for the design phase, not necessarily for the prepress phase.

Exporting to a PDF saves you time, duplicated files (original images on RGB and converted images to CMYK) give you the flexibility to change color profiles, make modifications to source files, protect the project vs unwanted changes on fonts, etc.

Answer 2

The problem with jpeg has nothing to do with print production, but rather signal degradation: when the image is saved, closed and flushed out of memory and subsequently reopened and decoded in preparation for editing, it is an imperfect reconstruction of the image that was in memory at the time of the previous encoding. This is compounded every time it is saved. Very similar to duping mix tapes in the dark ages of the previous century.

It is not a big deal in many cases, and they can mitigate it by always using high-quality settings, but they ought to know why and how it happens so they can make reasonable decisions about workflow. Mainly out of habit, I usually store in a lossless format (TIFF with LZ compression usually) but frequently emit jpeg versions from these "masters" for other uses. Jpeg will print fine.

A minor issue is that CMYK JPEGs are not as universally supported in software as RGB. They should be prepared for this since many times the software will still open the file but the color looks broken somehow.