I have been making phole images for a few years, and have several home-made boxes. I projected all the pinholes on the wall, got an exact measurement of size, did the math to figure out the optimum "focal length," and inspected the pinholes under a microscope for any defects. I'm happy with the images, yet they don't appear as sharp as some others I see. Talking physics with the neighbor, he said that I would get a sharper image if I filtered out one of the primary colors. He said since I have all these different wavelengths squeezing through the pinhole and overlapping, if some were eliminated the result would be a sharper image. Well, I do that already. I shoot mostly landscape and cloud movement, so I have R25 filters on everything. But. . .since I'm filtering the shorter wavelength part of the spectrum (blue), and allowing the longer wavelengths (red) to pass, is this the cause of a less-than-sharp image? I guess that is my question: when using a pinhole aperture, will shorter wavelengths produce sharper images than longer ones? If so, I need to start culling 58mm polarizers from the junk sales. Love to hear some ideas on this.