dpi? (computer talk)?

Question

I was asked to send a picture via email with a resolution of 300 dpi.

Answer 1

300 dots per inch is a common resolution for graphics.

Answer 2

(Dots Per Inch) The measurement of the resolution of display and printing systems. A typical CRT screen provides 96 dpi, which provides 9,216 dots per square inch (96x96). Flat panel displays from 110 to 200 dpi have also been developed.

Double the DPI, Quadruple the Dots

As the dpi rate doubles, the number of dots within a square inch is quadrupled, because dpi deals with two dimensions. Thus, while 100 dpi produces 10,000 actual dots per square inch, 200 dpi produces 40,000 (see below). We have a long way to go to make the resolution on a screen as dense as a printer. A 1200 dpi printer produces 157 times as many dots of resolution as a typical 96 dpi screen.

Dots Per
DPI Square Inch
96 9,216
100 10,000
200 40,000
300 90,000
600 360,000
1200 1,440,000

Answer 3

DPI = dots per inch (although it doesn't really turn out to be that)
The higher the dpi, the bigger the image file will be.
Most images on the internet are of a low dpi.
If you have taken a photograph with a good quality digital camera and need to print at A3 or A2, then a dpi of 400 or more is needed to preserve the quality of the print.

Jonathan

Answer 4

dpi only applies when you can garantee the size of the dots. On people's computers, you cannot, so the same image may be 3/4 the size on my computer than on yours).

When you print images, DPI means everything because the size of the page is well-defined. For a decent photo print, 72-150dpi is marginal, 300 is good, 600 is excellent and anything more is wasted.