Colours are very important in our work. In our opinion if you get the colours right in a video it gains a lot in quality. You don’t have to know everything about colours but it is very useful to know a bit about colour theory and even the technical aspects. In this article we are going over what we determine as important knowledge for film and photographic productions.
Everyone must have come across the three primary colours and the two contrasts black and white once in his lifetime. And surely you must have caught a glimpse of the colour circle too, where additional colours are added to fulfil the colour palette. As we work mostly with the Adobe apps, we constantly come across the colour wheel in one form or another.
But now let’s get started with our knowledge about colour theory.
First, we find it immensely important to understand the primary colours because they are considered the strongest colours. According to the colour circle of Johannes Itten the primary colours are yellow, red and blue, as they cannot get achieved by mixing other colours together. But in the digital world it changes a bit, due to the fact that the colours get achieved by adding colours in form of light (additive colour mixing). In the print world the colours get created by subtracting, or absorbing, light. Which is known as subtractive colour mixing.
So, we have red, green and blue (RGB) as the primary colours in the digital world, whereas we have cyan, magenta, yellow and black pigment to further absorb light (CMYK) in the print world. Further we are going to focus more on the RGB colour circle.
Most of you might know that if you google colour circle you find pictures like the one below.
Those circles contain not only the primary colours but also the secondary colours. Those are the ones that result from mixing two adjoined primary colours. Red and green result in yellow, red and blue in magenta and green and blue result in cyan. Mix them all together equally and you will get white light.
The colours get split into warmer and colder colours. In the example above they are split horizontally. The top half shows the so considered warm colours and the bottom half shows the cold ones. We will come back later to why this is important to know.
The colour circle is a very helpful tool for working with colours. It is also very important what information you can get from the positioning of the different colours.
First, you can read which colours complement each other. You just pick the colours that lie opposite to another and you have colours that work together and appear more vivid. But … what you will find out if you try it for yourself, you have to be careful in which ratio you combine those two colours.
Secondly, you can find out which colours you need to combine to get your desired colour. This knowledge helps a lot in colour grading. If you want to change the look of an image you know in what direction you need to push the colour to get your desired result. For example:
If you have a lot of green tint, you can eliminate it by just turning it down or you could push it towards yellow to get a warmer image or push it towards blue to get a colder look.
After this brief introduction into colour theory, we will continue with what that all means for us as filmmakers and photographers.
All digital cameras take the colour they see and convert it into data that the computer can decode to spit out the colour again. For filmmakers and photographers, it is important to get as much information about the colours captured as possible. That is why we try to capture most of it as RAW files.
When you photograph in RAW you will have the ability to change the colours quite a lot in post-production. The same goes for video. We will focus mainly on the capturing of colour in video.
So, if we know that we want to go over the footage with an extensive colour grading we have to choose the right Codec for filming in the first place. Colour can get captured in a lot of different aspects.
First of we are going to focus on the depth, which gets measured in Bits. 1 Bit stands for two states that a colour can have. If you imagine yourself an LED diode for each of the three primary colours, they are either on or off. For example, red is either red or black (off). If you were ever to capture in 1 bit colour depth you would be extremely limited during the grading process. That’s why the most common bit depth today is 8 bits. There is an easy formula to get how much possibilities you will have in your grading room.
1 bit = 2 states per primary colour diode (3)
1 bit = 2^1 = 2 different gradations per colour (on or off)
8 bits = 2^8 = 256 different gradations per colour
If you want to know how many colours this means you just extrapolate by the 3 primary colours:
8 bits = (2^8)^3 = 16’777’216 different colours (roughly 16.8 Mio.)
Now enough with all the math. We just need to know, that the more bits we have the more colours will be captured (and displayed). With all that information comes a lot of data too. So the bigger the depth the bigger the files will get.
Another important aspect to capturing colour is the so called chroma (hue and saturation) subsampling. This concerns whenever you hear us talking about capturing something in for example Apple ProRes RAW 4:4:4.
Whenever you hear 4:4:4 there is no chroma subsampling but if you hear 4:2:2 or 4:2:0 there is some chroma subsampling. The chroma subsampling compresses different parts of the colours captured to save some space on our hard drives. Usually, it is shown in a 4x2 rectangle like the one below.
We are surely no experts in this part, but we know what it does and what information gets compressed. So, as the human eye is more perceptive to luminosity differences than to colour discrepancies it offers a great opportunity to compress only the chroma information. The first number always represents the luminosity sampling, whereas the second and third represent the chromatic information.
For a 4:2:2 subsampling this leads to some minor detail loss. It is still high quality footage, but generates smaller files.
We like to have as much colour information as possible, because we really want to have some freedom while grading the footage. It gives us the possibility to transport emotions and give the whole video a defined look. For every project we try to distribute the given budget towards what we really need and try not to save money with cutting down on recording devices.
With the knowledge about how colour gets recorded we can easily work around compressed material. All it means is, that we have to work differently on set.
