The source of the stills is 1920x1080 footage (Originally 4k, brought down to 1080p. No chance of going back to 4k sadly). So, here's the three possibilities I have, and I'm wondering which one is better:
Option 1 - I go with 150dpi. And scale down (to 69%. Meaning a 31% decrease) the 1080p stills to fit the design.
Option 2 - I go with 300dpi. And scale up (to 140%. Meaning a 40% increase) the 1080p stills to fit the design.
Option 3 - I choose a weird dpi number, like 220dpi, so at least I don't have to scale down the original 1080p stills. But, I'm not sure this will be accepted by the company which will print it, or if it will make a difference.
Option 1 looks the best on my screen obviously. However, if 300dpi is a big difference, then surely the pixels I lost when scaling the stills down 31% to fit the 150dpi design should be a huge loss? Or? But Option 2 looks really bad on my screen. So I'm not sure... I could try BenVista Photozoom to get a better looking image on the screen, but it might change the image drastically when printed?