What resolution is needed for custom banner printing?

Answer 1

If it is vector you will not have a problem.

If it is raster image then 100ppi (not dpi – that is the printer specification) will be okay but would be better with text added as vector.

Answer 2

If it is a 10 metre long banner then 70dpi will be OK, as it is designed to be viewed from a long way away. 150dpi for smaller banners.   It is best to start with a camera image as large as possible with perfect focus and exposure. Anything over 20 megapixels should be fine.  If you want to print the image as a larger format photo to be viewed in a gallery, then use 300dpi in Photoshop or other image editor.