It's common knowledge that overdeveloping film will increase contrast, right? But why and how does that happen exactly? And maybe even more interesting, why doesn't paper show the same effect? I never time paper development. But even if I leave the paper soaking for some extra time in developer, I notice nothing like increased contrast. Maybe the whole image gets a tad darker, but that's it. Why is film different? What happens when you develop it for 5, 10, 20% extra time? Do just midtones turn darker on the negative? I can't imagine shadows (light areas on the negative) become lighter on the negative with longer development, which would really mean the contrast has increased...?