"virtual pinhole" with litho film?"

Has anyone ever tried making a "virtual pinhole" by making a clear spot in litho film? What technique did you use for creating the clear spot?

Would not the black of the lith still let some light in on a long, long exposure and add a bit of fogging? Also, will the clear spot soften the light by acting like a filter made of film? However, it's an interesting idea and could provide an uniformity to pinhole photography and lith film has an incredible resolution. Meanwhile I'll stick to Captain Beefheart singing about his Clear Spot.
http://www.youtube.com/watch?v=RqYfmfEqi20

Never tried it. Sounds like an interesting experiment.

I suspect you'll get a lot of diffraction from the fact that the film is much thicker than the foil most pinholes are made with.

Tried it with a zone plate. Horrible results as the film just isn't optically clear enough. I have some glass plates for lantern slides I mean to try out.

I think the film I used, Arista premium lith, wasn't suitable. Kodak 'line film' would probably have been a better choice.

I think commercial zone plates are made on some sort of lith film - that may be the reason for their overly diffuse imaging.