I got a request from an external company to render some of our images higher resolution to print posters for a fair.
They need: 3000mm x 1500mm @ 1200dpi
That's 142.000 pix by 71.000 pix ...
RIGHT ! I think not ... 120dpi for a poster is probably high enough me thinks :p and even for a poster that size, 60dpi would even be high.
Happens all the time to me. I was rendering some phones for roadside billboards and the product manager insisted they needed final size at 300dpi.
After I raised a big red flag, they did a little research on what the printer they were working with actually wanted and was down to 35dpi!