I 'wasted' lunch hour reading a history on the declasifed pages collection of the NRO's site.

The original film was rated at ei 3.6, and 110 line per inch was I think the unit used. The later film, available in 68 was up to ei6 and 130 lpi.

I think the resolution was more important, because they were imaging from 90 miles up, with something like a 77 inch lens that was steerable.

There was a discussion that you could pick out a place kicker at a high school football game lining up for a kick , and then on the next pass of the bird, a bunch of players linedup for first downs.