This may be a naive question, as I am not familiar with photography using negatives storing the photo images.
So in the film of "The Secret Life of Walter Mitty", Walter Mitty examines the negatives of photos in the bright sunny day.
How can Walter Mitty examine the negatives of photos in the bright sunny day without destroying the negatives? Is that due to some protection covering the negatives? Or particular materials or chemicals of the negatives? Or other reasons?
p.s. it will be the best that the answer can be more chemistry-oriented, explaining the chemical process.
(photo resources by googling -beware a spoiler for the film):