300 DPI vs 600 DPI
For photographs, 300 is enough: a 600 DPI photo print looks the same and the file is four times larger. Use 600 for line art, small type, and scans you plan to enlarge.
| 300 DPI | 600 DPI | |
|---|---|---|
| Pixels in an inch | 300 | 600 |
| Pixels in a centimetre | 118.1 | 236.2 |
| Pixels in a square inch | 90,000 | 360,000 |
| 4 × 6 in photo | 1200 × 1800 | 2400 × 3600 |
| A4 page | 2480 × 3508 | 4961 × 7016 |
| US Letter page | 2550 × 3300 | 5100 × 6600 |
| A4 in megapixels | 8.7 | 35 |
| A4 uncompressed | 25 MB | 100 MB |
| Pixels blend from | 11.5 inches (29 cm) | 5.7 inches (15 cm) |
600 DPI has 4 times the pixels of 300 DPI at the same print size. “Pixels blend from” is the distance at which 20/20 vision stops separating them.
When 300 DPI is the right choice
- Photographs and anything with continuous tone.
- Files where size matters: 600 DPI has four times the pixels of 300 DPI.
When 600 DPI is the right choice
- Black-and-white line art, logos and small text, where edges are either ink or paper and stair-steps show.
- Scanning an original you want to print at twice its size: a 600 DPI scan printed at double size is 300 DPI.
- Scanning documents for text recognition of small print.
Why
A press prints a photo through a halftone screen, typically about 150 lines to the inch, and the usual rule is two pixels for every screen line: 300. Pixels beyond that are averaged away by the screen. Line art is different: it is printed as solid ink at the full resolution of the device, so it keeps gaining sharpness up to 600 DPI and beyond.