by Oliver Spicer.
When the debate between shooting on film or with digital cameras is brought up, similar arguments are always cited. Physical film has a desirable grain that gives every frame a sense of liveliness, a different range of colours and contrasts more comparable to the human eye, and its irreversibility combined with high cost leads to every take having a sense of importance. Whereas digital cameras are easier to learn due to their instant results, the low cost of storage means more takes to get things right, and the digital formats produced are easier to edit with and distribute.
However, there are many aspects of photographic film that are completely incomparable to digital. For instance when resolution is discussed in the digital format it corresponds to the number of rows and columns of pixels that make up the picture, whilst film is formed from an irregular pattern of differently sized crystals that has no fixed 'resolution' - furthered by the fact that each size and sensitivity of film stock has a varied amount and size of crystals.
Therefore to fully understand their differences, a look behind the structure and chemical processes of film is required - offering a more detailed insight into their differences and what made film function before the transition to digital formats at the turn of the 21st century.
Film consists of a long strip of frames, with each frame formed from a mixture of Silver-Halide crystals suspended in liquid gelatin spread on top of thin transparent plastic. Although commonly referred to as an 'emulsion' - this mixture is actually a colloid, small insoluble solids inside a liquid as if the crystals were grains of mustard suspended in a salad dressing.
These crystals are where the important reactions take place in the film, formed from Silver-Halide compounds. Silver is a transition metal located in the centre of the periodic table, it has a variety of applications from medicine to jewellery - but it is most useful here due to its single electron on its outer shell. A Halide is a compound formed with Halogens, Group 7 on the periodic table that includes elements such as Bromine (most common for film), Chlorine, and Iodine. Group 7 Elements also means they have 7 electrons swirling around on their outer shell.
Electrons (small negative particles very important in reactions) in atoms are organised into 'shells', groups that have the same energy that orbit around the central nucleus. Individual atoms aim to gain a full outer shell to become more stable, with the Halogen requiring one more electron to add to its seven others and Silver wanting to lose one to make its inner shell considered full. This means when Silver and a Halogen are together, Silver gifts one electron to the Halogen to satisfy their mutual desire for full outer shells. However, due to the charge of electrons the Silver becomes positive due to losing a negative charge and the Halogen becomes negative due to gaining a negative charge. These charged atoms are called 'ions' and the Silver and Halogen will attract each other due to being opposite charges, forming a strong ‘ionic’ bond.
If enough Silver and Halogen particles form together, they will create a regular structure called a 'crystal' that holds the compounds in place but importantly allows electrons to travel through.
As the film is fed into a camera, the shutter opens to briefly allow light to hit the film (called 'exposing' it) before closing and moving the next frame into place - an action that occurs with precision 24 times a second to create the illusion of movement.
All light is made from a stream of particles called photons. When a photon hits a Silver-Halide compound in the crystal, the Halide will absorb the photon and use its energy to release an electron. The electron then combines with a positive Silver Ion to revert it back into its neural atomic form (often called ‘Metallic Silver’).
If this occurs several times in the same small area, the density of Metallic Silver increases and a 'Latent Image' is formed - where the areas of light and darkness are replicated by the density of silver but are still invisible to the human eye. To make this image visible, a series of chemical processes are required called 'development'.
Developing Agent is the primary chemical added, which turns more Silver Halide compounds Into Metallic Silver with a process known as reduction (adding electrons). It splits more Silver-Halide compounds where the initial reaction due to light has already begun, leading to making the exposed areas lighter whilst ignoring the unexposed areas - overall increasing the contrast of the image. Preservative aids the developing agent by preventing it from being oxidised (losing electrons) in the air, allowing the reaction to be more effective.
Accelerator creates the correct conditions for the developing agent by freeing up electrons in the Silver Halide compound - speeding up the process of the reaction. Restrainer is the opposite of the accelerator, preventing the development from occurring too quickly so the image does not look too light by causing reactions in places that were initially unexposed.
The development process is then halted. First, a 'stop bath' prevents any further reactions from happening in the crystals. Then the fixer stabilises the image by removing unexposed silver halide, which otherwise will appear foggy over time in sunlight. Finally all the chemicals are washed away in cold water.
The ratios of these chemicals, along with their strength and the time period in contact with the film, must all be balanced to form the best image - with this balancing becoming an art within itself necessary to create certain aesthetic effects in post production such as the level of contrast. For home labs wine, beer, and coffee can be all used as developing agents due to their chemical composition - all creating a unique look for the images produced.
After development, we are left with a negative of the film - an image where all the contrasts and colours are inverted. This can be reversed by using contact printing (that gives quick but low quality results) or through the use of an enlarger (that can also increase the size of the film for projection) with both methods working by shining a light through the negative to invert the image onto another roll of film called the positive.
On areas that were originally exposed to a lot of light, there is a larger density of Metallic Silver to block out the light being shone on the negative, meaning less light is let through to the positive causing a lighter area when projected - completing the set of steps required to reproduce the image on-screen by recreating the original areas of brightness.
There is an almost magical quality of photographic film brought out through a chemical analysis of its fundamental properties. The complex steps required to create an image highlights how amazing the replication of the world on-screen is (and that’s not even going into the further complications of colour film or how sound is embedded in later stocks. ) Through looking back at how cinema once functioned, we are brought back to the position of the first audiences of film: mesmerised by the simplest of shots due to the sheer achievement of creating the illusion of re-creating an image on-screen.
This awe-worthy aspect to photographic film is only emphasised by the fact that the inventors of these processes had no insight into the actual mechanisms that caused the images to be reproduced - with photography being developed in the 1830s nearly seventy years before J.J. Tomson even discovered the electron in 1897. Methods to reproduce reality with photographic film was only created through a long series of trial and error experiments, with a sense of mysticism embedded in the discoveries such as William Talbot noting how taking a picture of three people took the same amount of time as a single portrait - as if the presence of multiple souls took longer to embed in the film.
However, It's hard to suggest that film is still relevant today, relegated to a few cinema purists in Hollywood (such as Quentin Tarantino and Martin Scorsese) and works focused more on artistic value. That being said, looking not only back but also zooming into film does offer an insight into what makes it so special.
by Oliver Spicer, June 2022.
William Henry Fox Talbot, The Pencil of Nature (London: 1844)
Nichole Marie Witten, The Chemistry of Photography (Columbia: 2016)
John Beaver, The Physics and Art of Photography (Bristol: 2018)
Giogio Trumpy, Photographic Film and Its Iteration with Light (Basel: 2013)