Quote Originally Posted by Gerald C Koch View Post
Any pinhole that is not perfectly circular will produce less than optimal results. Such a pinhole would be impossible to achieve with an iris type aperture.
What would be the ill effect of such a polygon compared to a circle?

Leaving issues of thickness aside (!), one would overlay a pinhole of optimum diameter (mean diameter areawise) with pinholes of other sizes.
Keeping in mind that the pinhole diameter is calcaluted for a single wavelenght anyway, I would not expect any ill effect.
The same goes for the distortion imposed by the edgy shape of the polygon.