It seems to me whether the pinhole forms an image depends on your
definition of image.
If your definition of "real image" includes that light falling on a
particular point in the image has converged on that point, then I guess
a pinhole does not form an image. But that's not my definition of real
image.
My definition of real image would be more like... Light passing through
a particular point on the image came from a particular point on the
object. That is, I see the object-image relationship as a one-to-one
mapping of light from one point on the object to one point on the image.
A pinhole does that. A pinhole does not do that perfectly, but as John
Denker said, a lens doesn't do that perfectly either.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu