Packed into a tiny space is something that means a great deal to many of us. Its myriad possibilities are revealed once we possess it. Film! This magical and unique object. We all love it and can only be amazed at the results that can be obtained from a small but mighty canister.
Have you ever wondered how photographic film is made? We'll take a look into the making of a film emulsion and all the steps involved. There are many parts to the process and none of it is easy. It involves rare knowledge of chemistry to be able to create a satisfactory film.
The Emulsion and the Base
The film we load into our cameras is made of two main parts: The emulsion and the base. The base is usually made of cellulose triacetate, acetate, or polyester. It's a synthetic support that hosts and binds the emulsion. It is designed to endure winding and re-winding in the camera. The most important characteristic is its ability to stretch, while keeping a clean and uniform translucency.
Another quality is that it needs to be tough and resistant to scratches (as much as possible). It needs to have as much longevity as possible while it protects the paste, and allow the emulsion to be active. It is made with plastic pellets that when melted can be subsequently stretched and cooled, until the desired final size is reached.
Film emulsion is made up of chemicals combined to make a light sensitive paste. (The paste is the substance consistency at raw state when they blend the emulsion.) It is during the process of mixing the paste that we yield our blend sensitive to the whole light spectrum, as naturally, the crystal halides are only sensitive to the blue part of the light's visible spectrum.
Photographic film emulsion is built up of multiple layers of this specially formulated light sensitive paste. Each layer will capture the correct corresponding photons to their dyed silver halides, that will allow light to be transformed while going to the next layer until it sets.
Silver halides are made by precipitating silver nitrate and halides ( there are many possible combinations of different halides ) to make ionic crystals. These are mixed with water and gelatin, which acts as a binder to suspend the crystals within each layer of the gelatin. By controlling the mixing of the chemical substances the crystals will have different sizes, and different sensitivity to light. The chemical components and their reaction will determine the film's characteristics: sensitivity, contrast, resolution, latitude, and reciprocity of the film.
When dyes were stably introduced into the emulsion around the 1940s, we were finally able to see the whole color spectrum (in black and white it's called a Panchromatic film .)
With color film, it is essential to work with color theory and color combinations to sequence the layers that will capture different wavelengths of each color. Other important layers are at the top, in between, and at the bottom, to control the photons, UV light, and anti-halation.
Each step of the production line is crucial and has direct consequences in influencing the final product. From the precipitation, to the mixing of the paste, to the coating onto the base, it is fundamental to work with machines that can deliver with care each step involved to ensure the success of the film.
There is an interwoven synergy between physical laws that plays an important role during the execution of each step. Thermodynamics, fluids dynamics, mechanical control, and lastly, photo chemistry. Each step must be completed in a controlled manner.
A good film must satisfy all qualities such as grain, sharpness, color scheme, latitude, etc. And to successfully achieve the final product there is a pool of knowledge involved that is of immense value.
Now is the time to grab your pack of film and shoot!