What does DPI mean, and how does it affect screen display vs print size?
Asked 8/5/2010
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I often see image resolution described as DPI. What does DPI actually mean, and how is it different for images viewed on a screen versus images that are printed? For example, how do DPI/PPI and pixel dimensions affect the final print size and quality?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
16y ago
2 Answers
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DPI, or Dots Per Inch relates to the dot density when printing.
To help better understand the relationship of DPI to pixel dimensions, take an 800x600 pixel image for example:
- Using 300dpi, an 800x600 image will print 2.6x2 inches.
- Using 200dpi, an 800x600 image will print 4x3 inches.
- Using 100dpi, an 800x600 image will print at 8x6 inches.
Notes:
- As the DPI gets less dense, or lower, the print quality degrades.
- The pixel dimensions don't change in the example, only the printed pixel density
- Extremely large prints may be printed at lower DPI because they are viewed at a distance
- When changing DPI in a photo editing program, you can choose to resample which will change pixel dimension, or, if you choose not to resample, the pixels remain unchanged, only the print dimensions change.
Originally by user626. Source · Licensed CC BY-SA 4.0
user626
16y ago
0
Generated from our catalog & community — verify before relying on it.
DPI means "dots per inch" and properly describes printer output density. For digital images and screens, PPI ("pixels per inch") is the more accurate term, though people often use DPI loosely for both.
For screens, the important thing is usually the image’s pixel dimensions, such as 800×600. Changing a DPI/PPI setting alone does not change how many pixels the image contains, so it usually does not change on-screen appearance.
For printing, DPI/PPI determines how densely those pixels are placed on paper. An 800×600 image printed at:
- 300 PPI prints at about 2.7×2 inches
- 200 PPI prints at 4×3 inches
- 100 PPI prints at 8×6 inches
So lower PPI makes a larger print from the same file, but with less detail per inch. Higher PPI makes a smaller print with finer detail. Very large prints can use lower PPI because they’re viewed from farther away.
Also, changing DPI/PPI in editing software only changes print size unless you resample. If you resample, the software changes the pixel dimensions too.
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