As an experiment, we took a photo using two rolls of 35mm Fujifilm Pro400H film, a standard roll, and one exposed to heat in a car for two days. As suspected, heat does have an effect, and below is an example of a test we did.

The Darkroom’s tips and important information on how to store film

Film can be in the heat without being ruined, but long periods of exposure will greatly affect it. As you can see below, the heat muted the colors, brought the contrast down, and had a significant impact on overall quality. As someone pointed out on our Facebook, it looks like an Instagram filter was applied. See below for other interesting reactions and comments from our Facebook post.

Photos were taken with a Canon EOS 3 / 85mm.