viewing perspective

i have a scene with a few objects - they appear fine in the distance but when I zoom in and rotate they appear slightly stretched and mis-shaped

any ideas?

Normal :
Have you ever taken a photograph with a fish-eye lens ?
You get a comparable result if your FOV is too big in OGL. Just reduce the angle of your view frustum to correct this.
You can also make a quick calculation to determine this angle depending on the ratio (user-screen distance / dimension of the screen) so that your objects don’t appear to be distorded.