150 DPI vs 300 DPI
Use 300 for anything read at arm’s length and 150 for anything viewed from a step or more away. A 150 DPI print needs a quarter of the pixels of a 300 DPI print of the same size.
| 150 DPI | 300 DPI | |
|---|---|---|
| Pixels in an inch | 150 | 300 |
| Pixels in a centimetre | 59.1 | 118.1 |
| Pixels in a square inch | 22,500 | 90,000 |
| 4 × 6 in photo | 600 × 900 | 1200 × 1800 |
| A4 page | 1240 × 1754 | 2480 × 3508 |
| US Letter page | 1275 × 1650 | 2550 × 3300 |
| A4 in megapixels | 2.2 | 8.7 |
| A4 uncompressed | 6.2 MB | 25 MB |
| Pixels blend from | 22.9 inches (58 cm) | 11.5 inches (29 cm) |
300 DPI has 4 times the pixels of 150 DPI at the same print size. “Pixels blend from” is the distance at which 20/20 vision stops separating them.
When 150 DPI is the right choice
- Posters, canvases and wall art viewed from about 60 cm (2 feet) or more.
- When the photo does not have enough pixels for 300 DPI at the size you want. A sharp 150 DPI print beats an upscaled 300 DPI one.
- Scanning documents that only need to be legible.
When 300 DPI is the right choice
- Photo prints, books, magazines and cards.
- Small text and fine line work, which show jagged edges first.
Why
Halving the resolution halves the pixels along each side, so the file has a quarter as many pixels and is about a quarter of the size. At 150 DPI the pixels of a print blend together from roughly 58 cm (23 inches); at 300 DPI they blend from roughly 29 cm (11.5 inches), which is why 300 became the rule for print held in the hand.