Former B&amp;W technician: All film is developed in complete darkness; it it sensitive to all wavelengths. The B&amp;W photo paper is not sensitive to red, which is what allows you to have a dim red light on while printing enlargements.<p>And yes, it takes time to learn to navigate the room and work in pitch blackness. Gave me a lot of respect for the blind. At school, we could develop one roll at a time, allowing for the use of small containers which would let you work within a dark bag for a small period of time. At the photo shop, they had a machine for processing film in batches of 10+, which required the entire room to be dark while loading it.<p>Modern film processors frequently don&#x27;t even require the dark box (unless the film canister is in really bad shape) - just stick it in, close the door, push a button. Remarkably slick.