Ressing up print renders

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  03 March 2018
Ressing up print renders

Just wondering how people approach print ready renders, which can take a long time, say A3 @ 300ppi.

Do you render at the true final resolution or do you render out smaller and then res up in Photoshop or something else?

Wondering what I can get away with to save time.
  03 March 2018
i do a lot of renders for print. even way bigger sizes than that. depending on the image you can scale it up to 200% in photoshop without noticing any difference in the printed end result at 300dpi. if you have a lot of sharp details in your image you might not wanna go that high with the scaling though. there's also special scaling tools out there which do a slightly better job than photoshop.
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  03 March 2018
The key factor is to know (ideally) how that 'print render' is going to be produced - and how it's going to be used...
If it is going to be used at normal reading distance, on high quality paper, and reproduced by high quality litho or digital repro - then yes 300 ppi might be required. If it's going to be a 2m wide poster on a display wall - 120 ppi, or less, might well be absolutely fine.

The whole '300 ppi' thing is really historical baggage these days. It was based on the fact that a good quality litho print in a magazine for example might have a halftone linescreen of 150 lpi ('lines per inch' - or 'dots per inch' (halftone dots)) - so 300 ppi (pixels per inch) was a nice 2:1 ratio of pixels to halftone dots for 'best quality'. These days there are plenty of printing technologies that don't use conventional halftone techniques, but use things like stochastic / FM screening, or continuous tone imaging of various sorts - so that number is much more flexible.

Even in a conventional situation 'requiring' 300 ppi - I'd fully agree with Seb - you can easily uprez CGI. It's much sharper out of the box than any conventional photograph : ) Rendering at 50% - 75% size and uprezzing is often perfectly acceptable.
  03 March 2018
To add to Mike's post, there was research done in the late 80s when the impact of resolution was higher, since computers where very slow and storage was expensive, and a few pixels more would make a huge difference.
What was found, and I replicated successfully, was that the lowest image resolution required for print, was the print resolution (LPI) x 1.55
So, as Mike said, make sure you know the print resolution and multiply that by 1.55 (for 150LPI, it's 232.5 PPI image)

Everything else is true as well. Upscale by 10-15% and nobody can tell...
Let's add all this up:
Printing at 150LPI = Render @230PPI (Pixels Per Inch) - @A4 = 8" x 11" = 1840x2530
Let's make it 10% smaller (1656x2277)

So, in theory, for a standard A4 150LPI print, you could render at 1800x2300
Follow me on Twitter@nosemangr - Watch me on Noseman's Youtube Channel
  03 March 2018
Depends what it's for, how large it will be printed, how close people will get, how long people will stare at it, what the image content is.

Yes, you can almost always render smaller and scale up if needed, how much depends on too many things. Picture of soft clouds and a sunset? Scale that up 200%, nobody will notice. Picture with lots of crisp brickwork patterns and detail vanishing into the distance, you have less space to cheat. Internal company image that 10 people will see to approve a product? Cheat away. Final artwork for a product seen by a million, don't cut corners. Single image flashed up on screen for 3 seconds as part of a music video? cheat. Slow moving 4k video in a shopfront where people will stare? Do the full res.

As for print. My general rule is that for A4, 1500x2000 is about the minimum you could get away with; and I do mean minimum, 2500x3200 ish is a better base. As an even more broad rule, 4000 pixels of resolution works decently across the majority of uses. Postcards, A4 print, A3 boards, A0 posters, tv screens, on screen images.
Matthew O'Neill
  03 March 2018
in our experience for detailed images scaling up doesn't look really nice.

so we use always 4-5000px render size (that's near A3 300dpi)
and for very big images around 7500px

for us this renders still fast enough and reduces any problems afterwards
V-Ray on FB::
  03 March 2018
I have needed to create banners at 20,000 pixlels wide at 300 dpi (agency's specs).

I was sometimes able to render at 1/4 tp 1/2 size depending on the image and used ON1's Perfect Resize to uprez and got great results. Apparently if you know your way around the unsharp mask tool in PS you should be able to get good results as well--but PR was a timesaver.

I also have used After Effects "Detail Preserving Upscale" effect in many cases and get really good results with that as well.
  03 March 2018
Originally Posted by JoelDubin: ... (agency's specs)....

= unrealistic, unnecessary, uninformed... :-)
The funny thing is that there is solid science behind these specs, and they depend on context. One too many times in my old life, I had to fight with ignorance and stubbornness, trying to explain these things.
I even won a hefty bet with an old school, traditional drum scanner operator (with decades of experience), who claimed he could tell the difference between a 230 and 300 api image printed in 150LPI... he lost :-)
Follow me on Twitter@nosemangr - Watch me on Noseman's Youtube Channel
  03 March 2018

Its just as easy to do it their way though (using the upsize method) and then everyones happy.
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