Why EDID is not trustworthy for DPI

Simo Sorce simo at redhat.com
Thu Oct 6 17:59:47 UTC 2011

On Thu, 2011-10-06 at 11:41 -0500, Bruno Wolff III wrote:
> On Thu, Oct 06, 2011 at 12:00:36 -0400,
>   Simo Sorce <simo at redhat.com> wrote:
> > 
> > My main use case here is video projectors, and in that case there is no
> > way on earth you'll ever know the DPI as it depends on the distance from
> > the wall, and again even if you knew the distance from the wall you'd
> > know nothing because the optimal DPI will also depend on the distance of
> > the crowd from the wall.
> What you really want to know is the resolution per angle or arc. And that
> would be relatively constant for a project regardless of distance from
> the surface it is projecting on.

No, I do not really care because the apparent size of stuff depends on
the distance of the viewer from the projected surface too, so having
that value doesn't really tell you how big you should display stuff.

Also I do not need to know the resolution per arc to know that 10 pixels
are always 10 pixel just bigger because the wall is farther, except they
are still too little for the job because the crowd is even farther from
the wall than the projector is :)


Simo Sorce * Red Hat, Inc * New York

More information about the devel mailing list