The negative or positive in the case of slide film embodies most of the analog contributions to hybrid photography. A final negative is comprised of several steps all of which impact the scanned image.
First, there is film selection. If you have a history shooting film, you already know that films have a variety of different characteristics such as color rendition and grain structure. While films have a published ISO, indicating the speed of the film, it is possible to shoot the film at a variety of speeds yielding a multitude of results. All of these attributes are unique to the analog world of photography. Digital enthusiasts buy software to emulate grain, but fail to enjoy the unique contribution film selection plays in the process of creating an image.
The second ingredient is the exposure of the film. Films are formulated to react at different film speeds or ISO/ASA settings. Often the grain size is implied by the speed – lower ISOs often result in finer grain. In a digital context, lower means less digital noise, however the two are not the same. When shooting film, the photographer can decide to shoot a film at a lower or higher speed than it is rated. For example a 400 speed film can be shot at 800. Film processing needs to be adjusted to accommodate this change, which results in yet another variant in how grain is structured (in the case of black and white film) or dye is shifted (in the case of color film).
Third, developer selection impacts the realization of the negative. People often read about cross processing where slide or color negative film is processed in the other’s chemistry. While color film offers less latitude, black and white film can be drastically impacted by developer selection. Some developers such as Kodak T-MAX and Ilford Ilfotec DD-X are said to create finer grain negatives from the respective brands’ films. Others such as Diafine are said to create a fantastic range of gray, excellent for scanning.
Finally, there is the actual film developing process. The recipe using the developer as part of creating the negative is a critical part of any film realization. Again, color offers less latitude when compared to black and white, but in any case the time the film is exposed to the chosen developer impacts the contrast, color and grain structure of the selected film. Color film is less tolerant of temperature shifts as well, so processing is more rigid overall. In all cases how the film was exposed impacts how long the film should be developed to compensate. That said, it is up to the film processor to decide the correct compensation for the intended effect.
Processing black and white film is relatively easy and while it has been several years since I did it, it was pretty much like riding a bicycle. Developing film, especially black and white, is a key part if creating the negative – outsourcing it relinquishes the creative dial to generics.