What aspect of film is most affected by humidity in storage conditions?

Humidity in storage conditions primarily affects film emulsion quality. The emulsion layer, which is a crucial component of photographic film, is sensitive to environmental factors, including moisture. Increased humidity can lead to several issues such as swelling or softening of the emulsion, which can negatively impact the film's ability to capture images accurately.

Additionally, high moisture levels can foster the growth of mold or bacteria on the film, further degrading its quality and potentially ruining stored images. It is vital for film to be kept in controlled humidity environments to ensure that the emulsion remains stable and functional for imaging purposes.

While other aspects of film, like thickness or color, may be influenced by exposure to various conditions, the emulsion is the key layer responsible for capturing and holding the latent image, making its preservation paramount to maintaining overall film quality.