Originally posted by bhbrake So, this was part of what I was thinking about- did the 645 medium format market drive landscape photography at some point that the 4:3 became a dominant size for large prints? I was told at one point that if you were a professional film landscape photographer, you were shooting medium format. I don't know what John Fielder, Thomas Mangelsen, or any of the other old commercially successful western landscape guys have traditionally shot with, though I think Ansel Adams used 6x6. I suppose most professionals crop the majority of their images, so it isn't necessarily that big of a driver though.
I believe Ansel Adams used a variety of film formats, perhaps mostly 8x10 sheet film (4:5 ratio). Large format cameras start with 4x5-inch sheet film. 5x7-inch cameras were favored with high end landscape photographers, too. This ratio was very popular for landscape photography. I wanted a 5x7 view camera for a long time but never could afford one. I would have been relegated to 5x7 contact printing, though, because then you have to buy a 5x7 or larger enlarger.
The 645 and 67 medium formats originate from the 120 format for roll film. 645 was shorthand for 6 x 4.5 cm, with a 3:2.22222 ratio; 67 was for 6 x 7 cm, with a ratio of 4:3.33333. The 6x7 is closer to square (1:1 ratio) than 645.