isn't your camera designed to have the same optical paths in the three colors ?

Paul[/QUOTE]

Polka,
Of course, you correct. The diagram attached to my opening post in this thread clearly shows this,as dose the camera itself. So I am clearly working with one distance. If I eliminate consideration of 3 different wavelenghts I need only consider a pinhole of optimum diameter for 12 inches. This is the distance from the lensboard to film planes with bellows totaly contracted. But I will also get some pinhole sizes acurate fore some bellows extention.
I have decided to get some specialy prepared pinhole for this project. And to not use readily availible laser-drilled ones. I wish to do everything right for this project.
Bill