In the realm of “alternate” and “lo-fi” analog photography, redscale refers to the technique of shooting color negative film upside down, resulting in a strong color-shift towards red due to shooting through the base of the film and the red sensitive layer (which is generally at the bottom when shooting emulsion-side up). The blue light exposes the layers containing cyan and magenta dyes, but the layer containing yellow dye is left unexposed due to the filter.
In 2024, Lomography is the only company that I know of is making pre-designated redscale film. However, I can’t seem to produce consistent and satisfying result out from using this film - both in 120 and 135 formats, and I blame it partly on the ISO rating of this film: Lomography “recommends” a range of ISO instead of one single rating. I know making redscale film was simply a matter of spooling an empty 135 cassette from a bulk or unexposed one revered (i.e. emulsion-side to the back) but I had not thought of making one until now.