Retro Film Technology

Recently I purchased a Kodak m35 camera, which uses film rolls that develop the images you take. However... I couldn't help but wonder how the image transfers onto the film, and how the film is developed. So, I decided to do some research!

What I found out is that the process can be split into a few sections:

1. What happens when you press the button

When you press a camera button, a light-proof box is opened which allows a small bit of light into the camera. It focuses the light onto the light-sensitive film roll. This is different from modern digital cameras today where optic sensors replace the use of film.

2. The chemical processing of film in the camera

Once the button is clicked, it allows for an instant of light to enter the camera. The film itself is coated with a layer of light-sensitive gelatin crystals mainly made of up silver halide which undergoes a chemical reaction when exposed to the small amount of light. The silver halides turn dark when exposed to light, and produce a dark image on the film roll. If there's darkness, the film remains light - that's why it's called a negative.

3. Development of the film outside the camera

Once the entire roll is filled, the film goes into the process of developing the images. The film roll is dipped into a solution of chemicals, which helps to develop the film. These chemicals are usually hydroquinone, phenidone, dimezone, sodium carbonate, and sodium hydroxide. The developed film gives you a negative image. It is essentially taking away the silver halides and making the image permanent, as well as eliminating the sensitivity to light.

4. How to transfer the image onto paper

The negative image has the ability to leave a shadow on photo-sensitive paper which leaves you with a positive image, where the shadows are dark.

This means that you end up with paper-based memories! Something quite retro, and something that has not been thought about for the last 10 years since the iPhone.