I hope this is the right forum

[Katarina]

But I realized we don't have an off topic area. I'm not saying we should have an off topic thread, but I guess we can use this area

[mr.pete]

Hello there Kararina. There is actually a section for off topic discussions. The Everything Else section at the bottom of the forum page. Enjoy

[clyde dove]

These are likely 'lantern slides".

In the distant past, in addition to flexible film, it was possible to purchase sensitized plates for use in large-format cameras, and some of these were available in reversible emulsions (that developed as positives for projection). They were available in a variety of formats - 3 1/2 x 4 1/4, 4 x 5, 5 x 7, 8 x 10, etc. They were designed to be used in special projectors that were the forerunners of the 35mm slide projectors that were so common in the 1960s - 90s.

This was done at a time before 35mm photography had become common. When 35mm was initially introduced, it was derisively referred to as a 'miniature' format and popular opinion was that it was inferior in quality. Large format glass plates, by contrast, were considered the ultimate in optical qality because they offered both generous size (for maximum resolution) and absolute flatness.

In some instances, people who used these plates subsequently hand colored them. It is still possible to purchase transparent oil paints and pencils designed for hand coloring photographic prints.

[Snouk]

Hello, welcome here!