How might this occur?
Originally Posted by trexx
Finely suspended dust particles inside the camera imaged by the infinite depth of field of the pinhole and reflecting light, like dust in beams of sunlight?
Less than perfectly smooth edges of the pinhole?
The first would lead to varying patterns, the second (if operative) would lead to identical patterns from picture to picture (when conditions bring it out). Your post was ambiguous. Are you saying the patterns of dots are in the same position from picture to picture (when conditions are right to create them)?