Quote Originally Posted by Cesaraugusta View Post
Beyond focal length and the physical size of the pinhole, I can think of several more aspects that when considered in the pinhole's design will most likely increase the sharpness (reduce defraction) in the projected image.

1. The shape of the pinhole.
2. The thickness of the pinhole plate material (at the pinhole)
3. The color of the pinhole plate material (at the pinhole)

Would someone care to elaborate further?
I'm just a newbie into pinhole photography but as for the shape of my pinhole, I've tried to get it as round as possible using a needle. For the material, I use the metal from soda cans and sand it down with an electrical orbital sander using 60 grit sand paper. This gets it pretty thin pretty fast. As for the color of the material, I usually paint both sides black. Below is probably the best shot I've done using the methods described.

http://www.flickr.com/photos/aaronmi...7625595921944/

The focal length for the camera it was taken with is 125mm and my new 8x10 camera that I built has a focal length of 190mm - which is what sparked the thread. Wanted to know if there was a reason why making a larger pinhole for the longer focal length would be beneficial. I think the pinhole diameter for the above shot was .46mm.