Michael, there is no magic developer. You have the triad of speed, grain and sharpness and you can only improve on 2 at one time. So, you are technically barred from reaching the peak of this pyramid.

As we worked on imaging even earlier than the '60s when I arrived, it was apparent that the knife edge was self limiting as it only gave information on the boundary of an image at infinite width on either side. But pictures are made up of bounded areas and thus the slits came into vogue. They gave far more information and still allowed the examination of the edge effects. Kriss published his first work on this in the '70s and work has since sped up. The reason? Total image content is a very important method of comparison with digital. With aliasing, and R/G/B separations it is the content of the image which is important.

Kriss' work is based on the work of Higgins, Perrin and others, but is the next step forward from the early knife edge exposures. I cannot hope to explain this unless I scan in the whole article and post it. It is packed with a lot of calculus. All I can say is that we used the methods I described and out the other end came figures relating to overall image quality based on these mathematical geniuses.

PE