I wind the film based on the number of turns. I found that two complete turns works well. Some people use a clicker that rides in the sprocket holes. Then they count the number of clicks. I found my way to work as well.
The focal length is about 30mm. The pinhole is 200 microns.
I live near Charleston, South Carolina. These images were taken at Magnolia Gardens, which is about ten miles from my home.
It turned out that the hole in the shutter, and the camera body was too small. That is the reason for the vignetting. I changed this by drilling the hole in the body larger, and then using a different shutter:
Here is an image after the fix: