Em 28/3/2012 22:28, Neil escreveu:
> Hi all,
>
> Last week I went to a sign expo and was looking at a *giant* (prob >15=20
> ft horizontal) LED display screen, as would be used for advertising.  It=
=20
> was made up of individual red, green and blue LED's in a grid.  But I=20
> noticed that in every grid "square" two diagonal LED's were red, and the=
=20
> others were one green and one blue -- ie: there were twice as many red=20
> LED's as green or blue.  But the image colors seemed normal to me.
>
> So why more red?...
> Is it possible that the eye perceives red less?  Perhaps over a long=20
> distance?
> Is brighter/more red used to make more stand-out advertisements?
> Did they just fill the grid spaces and reduce the brightness of the red=20
> LED's?
> Or...?
>
> Cheers,
> -Neil.


Some time ago, the ready-made RGB LED modules had two blue, one red and
one green LEDs, IIRC, because older blue LEDs were much less efficient.
Perhaps now the green and blue LEDs can be built more efficient than the
red ones?

By the way, Bayer filters have one blue, two green and one red cell.

In analog color TV, the luminance signal is made of
0.299*Red+0.587*Green+0.114*Blue.

Our eyes are really more sensitive to some colors than others, combined
with the fact that LEDs of different colors have different efficiency
explain the need for different arrangements.


Isaac

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.