OpenGL-ES change angle of vision in frustrum

Question

Let's see if I can explain myself.

When you set up the glFrustrum view it will give the perspective effect. Near things near & big... far things far & small. Everything looks like it shrinks along it's Z axis to create this effect.

Is there a way to make it NOT shrink that much? To approach perspective view to an orthographic view.... but not that much to lose perspective completely?

Thanks