Artwork is too low resolution
Cover artwork should be 300 DPI at the size it prints, not at the size it was designed.
What to do
- An image is only as good as its pixels spread over the printed panel: a 1200px wide image on a 6" panel is 200 DPI, two thirds of the 300 it needs.
- Enlarging a small image does not add detail. Source a larger original instead.
- The cover builder reports effective DPI for each panel as you place artwork.
Check artwork resolution — the tool in this app that settles it.

