Message-Id: <mailto:199408161328.IAA19688@library.wustl.edu> Date: Tue, 16 Aug 1994 08:16:15 EDT From: Robert Rosenberg <mailto:rarosenb@GANDALF.RUTGERS.EDU> Subject: Re: Resolution of devices To: Multiple recipients of list IMAGELIB <mailto:IMAGELIB@ARIZVM1.BITNET>
> I have a friend who is into electronic photography. Looking into some devices
> to purchase, he noticed that some use dpi and others use lines to specify
> the resolution(s) of the device. Can someone tell me what is the difference
> between the 2 measures and how they can be related. Pointers to any relevant
> reference would be appreciated.
> hisham...
> mailto:sueyllam@alex.eun.eg
>
The difference is that a camera has a field that is X dots (or lines) wide and Y dots (or lines) high--that translates into dots per inch (dpi) as you move closer to or farther away from the object you are shooting. A digital photograph of a stamp that fills the field of view, assuming the camera has a resolution of 1000 x 1000 and the stamp is 1" square, would have a resolution of 1000 dpi. A similare photograph of a building that filled the field of view, assuming the building is 100' high and 100' wide, would have a resolution of 10 dots per foot, or about .8 dpi. With a scanner you set the dpi, not the resolution of the field, so that no matter what you put on the platen the resolution is the same--a stamp, a dollar bill, an 8.5 x 11 sheet of paper--once you set the dpi.
If that's too terse, there are more words where those came from.
Bob Rosenberg | Trying to understand learning by Thomas A. Edison Papers | studying schooling is rather like Rutgers University | trying to understand human New Brunswick, NJ 08903 | sexuality by studying bordellos. mailto:rarosenb@gandalf.rutgers.edu | --Mary Catherine Bateson