A 50 mm lens would be an extreme wide angle on 4x5 film.

Schneider makes a 47 mm Super Angulon and a 58 mm Super Angulon.

The image are on a sheet of 4x5 film is 95x120 mm, the diagonal is 153 mm.

Wide open the 47 mm Super Angulon projects a cone of light which cover a 110 mm circle. That would leave the corners unexposed. However, stopped down to f/22 the image circle expands to 166 mm, which will cover 4x5 film. The angle of view is comparable to (roughly) a 16 mm lens in 35 mm full frame use. Since you are limited to shooting at f/16 or f/22, and have a very narrow range of possible movements ( tilt, shift, rise, fall) this lens is used much more with smaller film formats. The 65 mm focal length is used more often and is made by several brands.

But this makes me ponder.

Oscar Barnack built his small camera for shooting landscapes while hiking in the mountains. He found the 4x5 equipment ( or the metric equivalent) that he was using just too bulky, heavy and a pain to carry. While a ‘normal’ lens for 4x5 would be 152 mm (6”), most cameras came with a 135 mm lens. Barnack chose a double (movie) frame format of 24x36 mm. This has an aspect ratio of 1:1.5. In contrast, the 4x5 image was 1:1.25, or somewhat boxier. With the 35 mm film he got about 15% more horizontal mage area. With a 50 mm lens on the 24 x36 image he could capture pretty close to the horizonal area that he would have gotten with a 135 mm lens on a 4x5. Assuming he used the full image area. If he cropped of the ends to make 8x10 prints he lost that. I have never read anything to suggest that Barnack entertained such thoughts, though.

Hardly holy scripture, but Barnack was interviewed numerous times over the years, and in rhe 30s to the 70s Leica put out a new book every few years. There are a lot around. And they are good reading.

Leitz parts bins at the time would have held microscope parts. There just weren’t any other 35 mm still cameras, other than the Ansco (Agfa) Memo, which was 18x24 mm, what was called single frame at the time, and we call half-frame now. When you are making something from scratch you need to make all the parts yourself, or draw up plans and send those to a machine shop. 50 mm lenses in the early days were rare. How times have changed.

50 mm lenses were not plentiful for enlargers, either. And a 35 mm neg needs to be enlarged. So it became common for people to unscrew the camera lens and use it on their enlarger. Why buy another expensive lens for the enlarger when you have one on hand? Apparently, So many people did this that 39 mm became the default mount size for other brand’s enlarger lenses.

I’m surprised he didn’t opt for a 24 x 30 frame size. That would have been the same proportions as the large format films—proportional to 8x10. I can’t recall reading any quotes from him about why he picked this shape. It could be there are some in German.

Perspective and perceived angle of view make the 50mm lens on a 24x36 frame "normal" or similar to how the human eye-brain will perceive it. In reality human vision has almost 180° with both eyes, or 130°. But the brain mainly "focuses" on what's in the center. There are gender differences with women extending their visual focus to a much wider view, and men tending to use the center 46°. There is a theory that this difference is physiological - with men evolving to be able to see movement and evaluate speed (closing distance if chasing or being chased) and women evolved to be able to see and recognized patterns subtle color differences in cluttered scenes. Think of cavemen going on a hunt or being hunted, and women foraging in the forest/jungle for nuts, berries and leaves to eat. TMI I know, but interesting to me at least.

If something looks 20 feet away to my eye and the XXmm makes it look <about> the same distance in the camera,
to me that's "normal".
Simple.

If it looks closer in the camera, that's telephoto, if it looks farther away, that's wide angle.
Don't need no charts.

Cloth focal plane shutters were around and in use on the early Graflex cameras, starting with Speed Graphic models in 1912. They fit formats from 3x4 to 5x7. Cutting one down would not be a problem.

However, since those were used with cut film they were simply slits cut in the fabric. You could cock the shutter with no film in the camera, or with a darkslide covering the film. With roll film one would put a lens cap on to prevent exposure from light passing through the open slit while the shutter was cocked. To avoid the need to block the light with the lens cap, a different type focal plane shutter, one which was closed when the shutter was cocked, and only opened for the exposure. This is also called a self-capping shutter.

Canon and Nikon copied the Leica shutter in their early cameras. Zeiss made one which moved vertically, which was duplicated by a Japanese firm and, with titanium leaves, used by Nikon, and now, a lot of the digital cameras, including digital Leicas.

Perspective and perceived angle of view make the 50mm lens on a 24x36 frame "normal" or similar to how the human eye-brain will perceive it. In reality human vision has almost 180° with both eyes, or 130°. But the brain mainly "focuses" on what's in the center. There are gender differences with women extending their visual focus to a much wider view, and men tending to use the center 46°. There is a theory that this difference is physiological - with men evolving to be able to see movement and evaluate speed (closing distance if chasing or being chased) and women evolved to be able to see and recognized patterns subtle color differences in cluttered scenes. Think of cavemen going on a hunt or being hunted, and women foraging in the forest/jungle for nuts, berries and leaves to eat. TMI I know, but interesting to me at least.