Resolution: 300 ppi at final size

Printers ask for raster images (photos, scans, painted illustrations) at about 300 pixels per inch at the size they will be printed. The key phrase is "at final size": a 3000 x 2000 px photo is 300 ppi at 10 x 6.67 in, but only 150 ppi if you enlarge it to a 20-inch spread. Check any image with the DPI calculator.

  • Photos and illustrations: 300 ppi.
  • Line art and scanned text: 600–1200 ppi in 1-bit or grayscale.
  • Full-bleed 6 x 9 in cover front: at least 1838 x 2775 px including bleed.

Upscaling a small image in software does not add real detail. If an image is too small, use it smaller or find a better source.

Colour: RGB vs CMYK

Screens mix red, green and blue light (RGB); presses mix cyan, magenta, yellow and black ink (CMYK). Some vivid RGB colours — saturated blues, greens and oranges — cannot be printed and will look duller on paper. Many POD printers accept RGB and convert it, but converting yourself with your printer's recommended profile and soft-proofing gives you control and fewer surprises.

Black-and-white interiors

For black-ink interiors, convert images to grayscale yourself. Uncoated book paper absorbs ink, so mid-tones darken (dot gain): lighten shadows slightly and boost contrast. Avoid tiny text inside photos.

Rich black and ink limits

Large black areas on covers look deeper printed as rich black — for example C60 M40 Y40 K100 — instead of plain K100. But never use rich black for small text or thin lines: any misregistration creates coloured fringes. Printers also cap total ink coverage (the sum of CMYK percentages) to avoid smearing; some POD services set the limit around 240%, so very dark, saturated areas may need adjusting.

File formats

  • Deliver interiors and covers as print-ready PDFs (PDF/X-1a or PDF/X-4 when the printer asks).
  • Embed all fonts; outline fonts on covers only if your printer recommends it.
  • Place images at 100% scale whenever possible and avoid low-quality JPEG compression.

Always order a proof

Screens are backlit and bright; paper is not. A printed proof is the only reliable way to judge colour, darkness and sharpness before readers see your book.