What is photographic film?

Photographic film is used in analogue photography to record and store a photograph. It is just one the the ways to take an analogue photo. Using film is probably the most popular analogue photography method. Photographic film – eh? What is photographic film? Do you know what photographic film is? Does it matter? Here we explore a little bit about photographic film.

Our techie (!) definition:

Photographic film
Photographic film is a flexible plastic strip coated with a layer of gelatin, which holds light sensitive silver salt particles in suspension.

We referred to the silver particles in our article ‘what is analogue photography?’ as being the means of recording and storing the light from a subject. They react with light to form the image of the subject being photographed. The photographic film is the means of being able to store, carry and use these light sensitive silver particles very easily. Either after manufacture, for getting to something worth photographing, taking the photographs, or right through to developing and making permanent the image on the film.

The different parts of a photographic film

A photographic film is manufactured on a precision basis and is constructed of different parts, all working together to enable the successful use of film to take a photograph. The different parts are quite complicated but, for us and for now, a simplified view of the construction will suffice!

A layer cake

Exploded view showing three layers of a black and white film

Simplified diagram view of the construction of a black and white film

Basically, a film is constructed of layers, one on top of the other just like a layer cake. Each layer will play a specific role in the photographic film. The number of layers in a film will vary from film to film, from manufacturer to manufacturer and for different uses e.g. colour film will have more layers than a black and white film. A film for x-rays will have different layers to a b/w film.For this article we are only going to look at the layers of a simplified black and white film.

Gelatin

Yes, gelatin! The lovely ingredient that is used to give a panne cotta its’ shape. This is also a key ingredient in a photographic film.

The purpose of the gelatin, in a layer, is to hold the light sensitive silver particles in place and prevent them from sliding about or even off the film!

The layer of gelatin can be rather sophisticated in holding the silver particles in particular arrangements especially in new(ish) films such as Ilford Delta or Kodak T-Max. These films use an arrangement that minimises the appearance of the particles in the finished print, referred to as the ‘grain’ of a picture. Older or more traditional films will have a less structured arrangement of silver particles – merely distributed throughout the gelatin layer evenly. There can be more than one layer of gelatin used, gradually added one at a time. This can help when different types of silver (salts) are used in the film e.g. silver bromide, silver chloride.

Plastic base

Many different types of plastic have been used for the base layer even cellulose nitrate! Yes, early films were coated onto cellulose nitrate which is highly flammable – this did make photography rather more dangerous than it needed to be! Old movie films made on cellulose nitrate would often self-combust (catch fire) when the storage tins were opened. Russian roulette film projection anyone? More modern films use an acetate or polyester based plastic as the carrier for the layer of gelatin. Much safer.

The main properties required are:

  • flexibility – to be able to be wound up into a roll;
  • inert – to be unaffected by the addition of the gelatin layer or chemicals used in processing, even heat used for drying a film;
  • stable – not to be affected by the chemicals used in development. Resist falling to pieces in storage;
  • transparent – not an obvious property but all photographic films will need to have light shone though them to be used or seen.

An anti-halation layer

A what?? No we haven’t suddenly got an issue with the halos of angels! Halation is a property of light where it spreads beyond its proper boundaries to form a fog round the edges of a bright image in a photograph. Light can use the layers in a film to spread away from where it is supposed to be which makes edges appear blurry and brighter. Similar to the angels halo in fact!

The anti−halation layer will prevent the light from travelling around within the film and deteriorating (or fogging) the recorded image.
There have been photographic films without an anti−halation layer, or at least a very weak one. Generally this is a bad thing. However, if it is known and worked with, the halos or fogging can be used for artistically using the ‘defect’ as a positive.

In our simplified look at what is a photographic film, our three layers, the gelatine layer, the plastic base and the anti-halation layer create a quality analogue film product. With advantages of portability, longevity and ease of handling.

Other films

There are other types of photographic ‘film’ which include sheet film – a single large sheet typically 5”x4” or 10”x8” which doesn’t need to be rolled up in the same way. Glass plates exist which substitute the plastic base for a sheet of glass, similar in size to the sheet film. Other photographic ‘films’ are less of a film than an emulsion. The emulsion has to be poured onto a base shortly before taking the photo and has to be developed very soon after exposure. Tintypes and daguerreotypes are made in this manner. These are way outside of our simple look at photographic film!

Is knowing this of any benefit in pursuing analogue photography?

Arguably, no. Though a yes would also suffice.

It is very possible to just use a film without really knowing about its’ structure or inherent properties. However, knowing a little bit about what a photographic film is can assist the photographer in making informed decisions about which film to use and how best to treat it. Also to be aware of its limitations.

The information about analogue photography is now easily obtained. This is true of really old processes like tintypes as well. It is not necessary to enjoy analogue photography nor to have fun taking good photos.

Load up a film and get out there and enjoy analogue photography – we do!

 

This has been a Hand Printed Photos production
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