creating banner image

The "300 ppi myth" has to be the most persistent in computer history.

No, you don't need 300 ppi at those sizes. In this case 100-120 will be more than enough. That's still a big file, much bigger than you get from any high end top-of-the-range camera.

Never upsample photos if it can be at all avoided! It's last resort, emergencies only. For one thing it's not necessary if it's decent quality from a decent camera, for another it inevitably introduces artifacts that only serves to reduce total quality.

The bigger it is, the further back you'll stand to take it all in. The optical resolution is the same. It's about degrees of arc in your field of vision, not absolute pixels per inch. Wall banners can be printed at 20-25 ppi and look magnificent.

EDIT: cross-post, but you get the point 😉

Why do you use 300 ppi for the banner?  The ppi required varies according to viewing distance. There is a simple formula - based on the resolution our eyes can see :

                 ppi required = 6878/Viewing distance in inches

So 300 ppi is needed for a viewing distance of 23 inches which is book reading distance. Will your banner be viewed that close?  If it will be viewed from say 5 feet then the ppi becomes 6878/60 = 115ppi. Anything higher is wasted it will not be seen at that distance.

Dave

You don't need a resolution of 300PPI for a poster that is viewed from a distance -- something like 50PPI or less would probably be OK. Have a word with your poster printer.