When film was first made (mid-19th century), it used silver-plated copper sheets that contained three layers with light sensitive chemicals on them. Other items used to create film included leather, paper, and glass sheets.
Glass sheets were the most popular due being cheaper and more opaque than plastic sheets. By 1895 “safety film” became the new norm as it was flexible and roll-able unlike the copper and glass sheets, and it was safer than nitrate film; however, it would take until the 1930’s for the modern color subtract film and positive film to finally develop. Even then, the film produced images that were too dark in color and would take an additional six years for Kodachrome, a film produced by Kodak that used color subtraction methods, to lighten the colors and film for more suitable images.
Gradually over time, the process and chemicals used for the processes to make positive photography became refined and better in terms of detail, resolution, lighting, and color. Special thanks https://guides.library.oregonstate.edu/earlyphotoformats/home