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Foundations of Thinking in Colour

This article is part of a series that looks a little bit of a closer at the basics of digitising colour negative film. Before we get into the technical side of things we will slow down and discuss thinking in colour as well as understanding colour. Later in this series we will walk through various hardware and softwares options for negative film conversions workflows.

Modern colour films consist of combinations of very thin emulsion layers each sensitive to respective parts of the light spectrum. These sensitivities have been adjusted to reproduce a particular colour response creating a set of dyes in the film under specific lighting conditions. The two types of colour film are reversal film (typically called slide film) which is processed to produce positive colour transparencies, and colour negative film which typically has been an intermediate between photographing in camera and producing colour prints. These days many photographers prefer to scan their colour negative film rather than print it in the darkroom. Despite the change in practice, the same principles hold and the knowledge and use of colour is still transferable between the fully analogue and the analogue-digital approaches.

The human vision system is capable of perceiving a very wide range of colours while effortlessly adapting to light sources of different tints and temperatures, while film records in a very literal way, with no adjustment for the light source or colour casts during the capturing stage. Therefore, it's important to understand that most films shot in anything other than daylight, will need further adjustment in printing or scanning to show accurate colours. Most colour negative films are daylight balanced which is appropriate for shooting in natural light and though there are still some tungsten balanced films left, few hobbyists make a deliberate choice between the two. Most films are therefore balanced at 5500 K (Kelvin) which is the colour temperature of a standard noon day, while typical indoor light tends to be much warmer, closer to tungsten lighting at 3200 K. When these typical films are shot indoors, the film itself will look very yellow on a positive film and very blue on a negative film - however, this is typically corrected by the operator when scanned, or in the darkroom when printed directly.

Converting Colour Negative Film

These days colour negative film is more commonly used than positive film, or slide film as it is called sometimes, due to better standardisation of the developing process, making it more accessible and affordable. Colour negative film also has a wider exposure latitude that makes it easier to shoot. However, the negative is just one step towards making a final image, so when scanning, the film has to be converted from a negative to a final positive image. A lot of people find this process of colour conversion to be a very tricky task. We are here to tell you that this is not at all the case. Colour conversion can be easy, painless and fast! We hope this series will provide you with the understanding and confidence you need to use the existing set of software tools to do this yourself.

Colour is by nature subjective and it can easily be overwhelming and difficult to get conversions just right. The key to succeeding in this endeavour, is understanding that this conversion process is interpretive. While a great deal of it is, and can be done automatically, you will still need to make some conceptual decisions. When you send your film to the lab, these decisions are done for you, by the scanning operator. Despite this, many film photographers strive to achieve certain aesthetics associated with the character of specific film stocks. While there are some discernible characteristics to a specific film stock, the truth is that the same negative can have a thousand different positive conversions and it is up to you, the photographer, to decide what your result will look like. This might sound confusing, but it is actually thrilling!

Accurate Colours

Because photography is such a broad field, there are many different applications of colour. While there are artistic colour uses and tonal representations, some disciplines require absolute colour fidelity, where the colours need to be portrayed as realistically as possible. For a botanist, who spends a lot of time photographing macros and plant life, the details and colours are very important. This might not be every photographer's goal but for this guide the task will be simplified by assuming that our goal is to accurately reproduce colour in our conversions. For other applications, experimentation is the only approach as there is no hard or fast rule to what a conversion should look like but there are some basics that will provide a good starting point. Working with colour is something that you grow into over time, and experience is required to develop and deepen your understanding of it as well as preferences for your work.

Splitting Colour Balance into Sections

For the sake of balancing colour, we tend to split adjustments onto two axis, both in the digital world and in the darkroom when printing colour. On one, is the tint - with magenta (a sort of purple/pink colour) on one side and green on the other. On the other, is temperature - with blue on one side and yellow on the other. Adjusting an overall colour cast - a general, overall imbalance towards one of these colours, is a matter of adding more of the opposite colour. For example, if we have an image with too much magenta, we want to add green to all areas of the image to compensate and make it neutral.

Taking this concept further, colourists tend to split into three further categories: shadows, midtones and highlights - these are separated by areas of brightness where the shadows are the darkest and the highlights are the brightest. By adjusting the tint and temperature in the shadows, midtones and highlights, we can adjust local colour casts. Luckily, tools for this has become very available with the advent of digital processing. Therefore, we can for example, have shadows that come out too blue - for that you can adjust add yellow to only the shadow areas of the image. Alternatively, maybe we have a blue sky that comes out too muted blue after we have adjusted the overall colour balance of the image - then we can add blue to the highlights, compensating for the yellow added to the overall image, by adding blue locally to the highlights. With these simple tools, you should be able to adjust any colour cast of an image. In the next articles, we will show you how to do just that in various types of software.

The Interpretive Process

Negative film inherently requires an interpretive process to create a final image. As part of the imaging process, the negative is only one step along the way, with the camera, lens, developing, scanning, post-adjustment and printing being others. The result of this interpretive process is, such as what we think of as Fuji colours or warmer Kodak colours, is to a large degree based on work done before us. These 'looks' were largely invented by engineers who worked on digital scanners in the 80's and 90's and earlier still, pre-digital, by engineers working on photographic paper for the printing of these films. The deciding factor with printing on paper was the inherent sensitivity of the different layers of colour emulsion, resulting in our perception of a specific film look, perhaps with saturated greens, warm skin tones and deep blacks, or with a warmer overall look, muted greens and a faded grey-ish black. Where scanners were involved, algorithms were tweaked to deliver results that they found to be most pleasing to consumers. These engineers certainly did their jobs well, and so it is often a good idea to be inspired by and try to emulate this aesthetic, but you should not take these results as the absolute truth of how the negative film looks like.

It is important to have a good understanding of your subject matter. If you have a good memory for what a scene looked like at the time of capturing it, it is much easier to know if your result is satisfactory. This leaves less interpretation for the photographer and simplifies the conversion process. In addition, it is important to "unsee" the whole, and see parts of the image as what they are: areas of colours. For example, taking a picture in a forest, a lot of inexperienced users will balance the image with too much magenta so that the brown paths take on a pink/red hue and the green trees are muted. Another example is taking a picture into the sea, say of a sailboat in the distance - here the dominant colour will be blue, and both automatic algorithms and in-experienced operators will try to compensate by adding more yellow, making the white sail of the boat too yellow and the sea a muted green-ish colour.

One can sit with a single image and spend an infinite amount of time trying to perfect it but you will become blind to the colour casts and artefacts. Work in smaller bursts and to revisit your images after your eyes have had time to readjust. This might seem tedious but you train yourself into it quite quickly. In our digital age it is worth keeping in mind that not all screens are made equal and many monitors differ in the way that colour is displayed. The same image can look very different on a mobile device, often not very true to the proper colour values. A great number of people consume media on cell phones people so we can be forgiven for being tempted to think that this is the best way to enjoy photography. Phone screens are very variable and the safest way to know your colours are good is to use a good desktop monitor. It is worth investing in one over time. Until then, it might be worth looking at your image on more than one screen, and try to adjust it to look acceptable on all.

The only way to improve is to get started! Luckily there are many online groups and forums specifically for the purpose of discussing colour conversions and it can be useful to get constructive feedback from your photographic community.


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