On Aug 21, 9:36*am, Chris L Peterson wrote:
On Sat, 20 Aug 2011 18:09:19 -0700 (PDT), Ron Cuaz

wrote:
Thanks. So at a distance of 5 meters. How do I know how big an area of
the object it would appear to a single pixel? What's the formula? ow.

That's just basic trig. For a subtended angle A, a distance D, and an
object of size d,

A = 2 * arctan(0.5 * d / D), or
d = 2 * D * tan(A / 2)

So for a pixel scale of 12.7 arcmin/pixel, and a distance of 5 m,

d = 2 * 5 m * tan(12.7 arcmin / 2) = 0.018 m = 18 mm per pixel.

Just for comparison to the human eyes. At the same distance of 5
meters. What area can each retina see? I assume a retina is like a
pixel in camera?

Sorry for being dumb in math.