Denis, what I am saying is that if one wishes to do colour sep with a pinhole and get optimal sharpness or resolution, you cannot not have optimal results for all three colours at the same d and FL. So you'd have to vary them in concert to get optimal results. Does it really matter? Maybe not :rolleyes: I was just relating a nutty idea I had at one point.
For fun, consider an apo-corrected lens as a counterexample: it has the same FL across the wavelengths, so no refocus is required for UV through near-IR. The foci at relevant wavelengths coincide. So in some sense, a pinhole is kinda anti-apo
P.S. That is an interesting idea, Nick. I had more in mind to have a pinhole mount and then three different discs with three diameters, and you'd just swap them out as you do your colour sep exposures.