What size in pixels is your Poster ? What size in millimetres is your Poster ? If you do not know look in Image -> Image Properties the top two lines Size-in-pixels / Print size
What size in pixels is the banner image ? Any sort of scaling up or down will introduce a distortion.
300 x 300 pix is not a large size for adding to a poster.
What size in pixels is the banner image ? Any sort of scaling up or down will introduce a distortion.
300 x 300 pix is not a large size for adding to a poster.