There is a well-worked-out solution to this, and as was said in a different message, the best lens is a certain meniscus (the ideal shape varies some with refractive index of the glass). With the optimum ratio of the radius of curvature of the two sides (and the correct orientation) the spherical aberration reaches a minimum. All other ratios will give worse images. Such a lens is not too far from PCX, but enough to make a difference. Many optical books show graphs of the variation and Warren Smiths'---------- does it particularly well. The trouble with surplus lenses is that you do not know much about them; rarely will you get information about the radius of each of the surfaces. If you go to fancier suppliers you do get the data but the lenses are not inexpensive. Incidently, I just saw a comment that a PCX should be cheaper to make than a DCX or PCX. I believe the conventional wisdom among the folks who really make lenses is that a flat side is at least as difficult to grind and polish as a curved side! You might as well gioi for the optimum form. In the end, the easiest way to get a cheap lens computed for the least spherical abberation is to buy an old camera lens (designed to be optimum for an object at infinity.) Bob Mueller Dr. Robert Mueller Institut für Festkörperforschung, FZ-Juelich D-52425 Juelich, Germany phone: + 49 2461 61 4550 FAX: + 49 2461 61 2610 email: [EMAIL PROTECTED] _______________________________________________ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
