cspear posted at 1:05PM Fri, 13 December 2019 - #4373084

Since I do this kind of printing for a living, let me throw in a few thoughts.

The 300ppi standard is based on really old requirements for photo-mechanical reproduction technology, where a 150 line screen was very common. A lot of the technology used for digital printing uses the 300ppi standard as the basis for its printing resolution, which can be 600dpi, 1200dpi, 2400dpi etc. Note the difference between pixels per inch (ppi) and dots per inch (dpi). Do not assume that you have to make an image (PIXELs per inch) match the print resolution (DOTs per inch).

A poster of this size is likely to be printed on an inkjet system, and it is highly unlikely that a regular dot pattern would be used for screening: it's almost certain to use 'stochastic' or 'frequency modulation' (FM) screening. Traditional screens rely on Amplitude Modulation (AM). AM means the dots get bigger to deliver more of a particular colour. FM means that there are more dots of a particular colour where required.

About 25 years ago I was involved in conducting research into how image resolution impacted on perceived printed results, and long story short, for most images the difference between the same image at 200ppi and 300ppi, printed at the same size using the same paper and ink (actually printed on the same page) was, if noticeable at all, negligible.

Images rendered out from 3D apps have not been softened by lenses, scanners, etc. so should not need artificial sharpening to 'improve' them.

A poster this size will be viewed mostly from a distance in excess of 1 metre and will not be scrutinised as closely as a print held in the hand.

Many of the more recent RIPs and print control systems have built-in upscaling engines which can, depending on the image, produce astonishing results even from poor quality originals. I did a job this week where a 900pixel x 600pixel image was printed at A3 (12in x 16.5in) and looked, well, not great, but by no means terrible.

With all that in mind, I'd be inclined to render out to 100ppi equivalent (2400 x 3600 pixels); keep the image in RGB, DO NOT convert to CMYK; and DO NOT apply any sharpening.

Thank you for the information you have provided, I have often wondered just how the printing was done in the modern day. I have been really pleased with all the printing I have had done and I tend to create a photo book of my renders each year. In the last few years I have created lay flat A3 photo books that allow a panoramic double page spread which can be stunning (as long as you remember to keep anything important away from the join in the centre). The site I use for printing will throw up a warning if the file I have uploaded would not produce the quality they are used to providing. It seems to work as I have yet to receive anything I am not happy with.

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.