How your films are processed (part 1)
If you shoot film, that’s something you might have thought about already. As film photographers we all know we need to go see a lab and let them process our roll for us (in most cases). However, how many of you know what exactly happens after you left the roll you just shot at the lab?
Have you ever wonder why your lab always ask you what film did you shoot? Or why it’s written C-41, E-6 or even ECN-2 on the small package we have when getting back our processed rolls? You’ll find out everything our guide to film photography in this series of articles dedicated to film processing.
B&W, negative & positive film
Let’s start with the basics, you already know that there are different kind of films: colours, b&w, slides, infrared, etc. Actually, the most important thing for the lab, isn’t the colour of your film, but the process it is made for.
Let’s start with b&w film. The composition of those films are the easiest ones to understand. The simplest ones are made of three layers: a light sensitive emulsion, a “plastic” support for the emulsion and anti-halation layer. The composition of the layers will vary depends on the film stock you use. All those layers will have an impact on the final picture you will get. The emulsion is probably the element the most important layer, without it, you wouldn’t have any image. For B&W films, the emulsion is made of silver halide that are able to catch the light and react while put into a chemical bath. The silver halide will react and become pure silver forming the image with shades of grey. The anti-halation layer is there to prevent the creation of halos due to the reflection of the light in any element of the camera.
The composition of colour negative films is a bit different and contains more layers. Actually, there is one layer for each main colour of the spectrum: cyan, red & green. Each layer reacts to the opposite colour of the light spectrum. There is a separation layer between each colour reactive layer.. The cyan layer is always separated from the other by a yellow filter that blokes the blue light. Each of the three main layers has light-sensitive silver bromide grains and a coupler that will form a dye during colour development: the blue layer dyes in yellow, the green one in magenta, the red one in cyan. The dying of each layer can affect the following layers. To compensate these secondary colourings, the red and green layers have a mask added. The other layers are exactly the same as a b&w film: the support and some anti-halation layer.
Positive films’ composition is really similar to the colour negative film stocks. You have a support, anti-halation layer, a colour emulsion, and a final protection layer. However, there is no separation between the layers of the emulsion.
As you can see, basically b&w, slides or negative films are kind of the same. They are made of a support base on which you’ll find an emulsion (itself composed of different layers), an anti-halation layer and a protective one. But, in the end, the most important thing for your lab is the process your film is made for. But that’s for another article. Stay tuned!