YUP as I recall ESTAR was the choice for several reasons.

Thinner base so the could stuff more frames into each back.

Dimensionally stable so that they could use photo
interpretive metrics to scale objects in photos.

And ESTAR is much tougher so less chance of a roll of film
breaking in camera.

And the stuff would be more like Aero-ektachrome than the
stuff we could buy.

darkroommike

Peter wrote:
On Aug 28, 4:56 pm, "Neil Gould" wrote:
Hi all,

I was puzzled by some comments in these articles about the Apollo mission
regarding the resolution of color film being scanned. Anyone here know
what was being used, and why a 2800 ppi scan would be "well past the
grain" of a 6x6 frame, as is claimed in these articles?

The site you referenced lists the colour slide films as
Kodak SO-121 Ektachrome MS and
Kodak SO-368 Ektachrome MS.

see: http://apollo.sese.asu.edu/RESOURCES/apollo_films.txt

These appear to be special versions of the Ektachrome films
of the time. I would guess that the big differences between
SO-368 and the Ektachrome-X that people used on earth
at the time are that it was on a polyester Estar base instead
of acetate and had a really aggressive UV filter layer .

http://apollo.sese.asu.edu/ABOUT_SCANS/index.html

Indicates a scan resolution of 100 pixels/mm for the
Ektachrome. I would guess that they tried higher
resolutions and didn't get any meaningful extra information.
This doesn't surprise me given what I know of the
Ektachrome films of the time.

The B&W films were mostly Aero Panatomic-X which
they are scanning at 200 pixels/mm.

At
http://apollo.sese.asu.edu/METRIC_PREVIEW/index.html

They estimate that the actual resultion on the films is
about 1/(2^.5) of the scan resolution. This would equate
to 71 lp/mm of useful resolution on the Pan-X - this is
very good for real-world performance on medium
format black and white film. It doesn't surprise me
in the least that the Ektachrome images are only
half that good in practice.

As for "well past the grain" - it can't be true in a
literal sense - the largest grains are quite a bit smaller
than a scanned pixel. But it might be beyond
the point where the graininess of the film becomes
intrusive.

Peter.
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