GlOrtho and glFrustum

Hi, all:

It was recently explained to me that while we typically do our thinking in a right-handed coordinate system, the screen is a left-handed coordinate system. One of the consequences of this
is that if you use

glOrtho (-1, 1, -1, 1, 1, 3)

and keep your drawing in the negative range (-3 < z < -1), then it works perfectly and you never get a near/far clip. The same thing applies to

glFrustum (-1, 1, -1, 1, 1, 3)

but it causes a problem. The resulting dimensions in the “perspective” view appear to increase with distance rather than decrease.

Can anybody explain this without a camera analogy? Can anybody explain how to do this (control z clipping and obtain correct perspective) without GLUT?