On Wednesday 27 October 2010 at 00:45, Paul Louden wrote:

> On 10/26/2010 5:40 PM, Antony Stone wrote:
> > I find this question hard to manage - isn't resolution a quantity, which
> > is measured in units of DPI?
> >
> > How can screens of different DPI have the same resolution?
>
> DPI means "dots per inch." Resolution is an absolute measure of dots. A
> 1280x720 16 foot projector has the same resolution as a 1280x720 9 inch
> netbook. But the DPI of them is drastically different because while the
> number of dots is the same, the physical area of the screen isn't.

I think you're confusing pixels with resolution.

Pixel (or dot) density refers to the total number of dots on a device (no
matter what size it is).

Resolution is the number of pixels (or dots) in a given distance or area
(usually inches).

A printer with a resolution of 300dpi is a 300dpi printer, no matter whether
it takes A6 paper or A0 paper.

A display screen with a resolution of 75dpi is a 75dpi screen, no matter
whether it's 1.5" across or 12" across.

From http://en.wikipedia.org/wiki/Display_resolution -
"the use of the word resolution here is a misnomer, though common"
"resolution properly refers to the pixel density, the number of pixels per
unit distance or area, not total number of pixels"

See also http://en.wikipedia.org/wiki/Pixel_density

Regards,

Antony.

-- 
If you were ploughing a field, which would you rather use - two strong oxen or 
1024 chickens?
 - Seymour Cray, pioneer of supercomputing
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