I wonder why NASA opted for an SLR when the modified versions would need to be operated through an external viewfinder. Same with the first Nikon Fs they sent up in later missions.
I guess they were the only option for solid cameras with high end lenses at the time.
"In the summer of 1962, Walter Schirra — who would soon become America's third man to orbit the Earth — walked into a Houston photo supply shop looking for a camera he could take into space.
He came out with a Hasselblad 500C, a high-end Swedish import that had been recommended to him by photographers from Life and National Geographic.
"He was sort of an amateur photographer," Jennifer Levasseur, a curator in charge of the Smithsonian National Air & Space Museum's astronaut cameras, says of Schirra. "Somewhere along the line, the decision was made that he could select what camera was flown on his flight."
Schirra's was a much more sophisticated — and pricey — choice than the simple Ansco Autoset that John Glenn bought for $40 at a Cocoa Beach, Florida, drug store. Glenn used it to take pictures from orbit on Friendship 7 in February 1962. The Hasselblad retailed for about $500 and used a much larger negative than Glenn's 35 mm camera. It also sported interchangeable, Carl Zeiss lenses and removable film magazines."
That’s a good point and as you say there likely weren’t any medium format viewfinder cameras. A twin lens reflex might have been easier to use but would have been much larger.
Oh, there were plenty MF viewfinder cameras. Plenty of folding cameras in particular, but also box cameras and some rangefinders. Just none that could feasibly be sent to the moon and be operated with astronaut's gloves.
Really the only one I can think of that could have worked is the Graflex Combat70[1], which is essentially a giant Contax that shoots on 70mm film cartridges. That one was developed for the American Military to be used in the Korean War.
The refractive index of air is really close to a vacuum.
The cameras likely just worked in a vacuum.
I would only worry about extreme temperatures (probably not an issue unless left in the sun for long) and outgassing causing fog on lenses or embrittlement of the film.
I would also be worrying about charged particles causing exposure of the film when not in use.
