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Ever wonder why I'm so fussy about 'clean' lighting with my coloured-gel photography? Simply put, failing to produce cleanly lit gel shots simultaneously produces horrendous-looking shots with gels.
When I refer to clean lighting, I'm referring to the fact that I like to keep all of my lights in my scene exactly where they're supposed to be. If I have a background light, then I have it lighting the background and nothing else. When I have a hair light, I have it lighting the hair and nothing else and so on. This might seem fairly obvious, but when you're using white-light and large modifiers like softboxes, the lighting is going everywhere whether you like it or not. You have a 5-light white-light setup, and you likely have the same colour white-light falling on all areas of the image, but because all those lights are the same colour, we barely notice. We simply can't get away with being that sloppy with coloured gels.
I will explain colour banding more thoroughly later in this article, but for now, just know that it's where adjacent colours don't appear to blend very smoothly. They 'step' quite aggressively, as you see here on this model's arm. The colour appears to go from blue to grey to orange, and this can sometimes be referred to as colour banding. But is that accurate?
So why do I insist on clean lighting with gels? Well, it's because when two coloured lights mix, they don't mix like paint, they mix like light does.
Not only do they not mix like we think they should, but they also start to produce an awful-looking side effect we call 'colour banding'. I'll explain colour banding and what it looks like in more detail later, but first, let's take a look at what I'm referring to when I say 'mixing' light versus mixing paint.
The physical mixing of colours is referred to via a 'subtractive' colour wheel, which is used to describe mixing colours like paint. Light hits the paint on a canvas and is reflected back into our eyes, and we see the colour that way. This is the regular colour wheel we're all used to seeing and using.
However, for mixing light, we use the term 'additive' colours, specifically referring to how light mixes from transmissive devices like TVs, smartphones, and so on. No light is reflected off any surface like a canvas, and the colour is mixed as we see it directly on the screen.
Take a look at the diagram below to see just how differently colours mix with paint compared to light.
Click to enlarge - It should be pretty clear to see just how differently red, green and blue mix when we do it with paint compared to light.
How do we create coloured light?
So, before we get ahead of ourselves, what is coloured light? The short form of this is that white light is actually made up of a full spectrum of colours. Basically, that means that when you shine multiple coloured lights on top of one another, you're actually just getting closer and closer to a white light with no colour at all. But don't worry, you're not alone if you think this is weird because we've all spent our entire early school years learning that mixing colours and paint is very different to this. We've been told that mixing colours like blue and yellow will result in green and that if we mix red and yellow, we'll get orange, and so on.
You can literally forget everything you were taught at school about colour mixing as it’s completely different when it comes to photography and mixing coloured lighting.
The diagram below illustrates that white light is, in fact, a complete rainbow (spectrum) of colour.
So, how does this relate to us as photographers? Take a look at the diagram above to get an idea of what coloured gels actually do to our light once it has left the flash. ‘White’ light leaves the flash and travels into the gel. As we mentioned before, white light is actually a complete rainbow (spectrum) of colour, so when it hits our red gel, the gel isn't actually turning the light red, but instead, it's filtering out all the other colours of the spectrum and leaving only red behind.
So now imagine the same thing happening with a blue gel and a green gel alongside this too, with their powers combined (they produce Captain Planet - if you get that reference you're officially old ;) ) they create white light once again on the resulting surface.
When RED, GREEN & BLUE light are combined they produce white light.
The Two Colour Wheels
Yes, that's right. You heard me correctly earlier on. There are, in fact, two colour wheels, and we need to understand how they both work, how they relate to one another, and what's important for us as photographers before we can continue.
I spoke about 'additive' colours and 'subtractive' colours before, now I'd like to try and explain these in terms that relate to us as photographers, so from now on, I'll be referencing 'subtractive' colours as the painters colour wheel and 'additive' as the lighting colour wheel.
First off, let's take a look at how the two colour wheels differ visually.
Click to enlarge
They're certainly very similar but there are a few key differences in the way the colours are laid out to illustrate how colour is mixed between them.
First, we should clarify the primary colours in both of these colour wheels. If you're not sure what defines a 'primary' colour, it's the core set of three colours from which all other colours are derived. In the painter's wheel, it's Red, Yellow, and blue, and in the lighting colour wheel, it's Red, Green, and blue (RGB).
Click to enlarge
Now that we know the primary colours for both the painter's and lighting colour wheels, we can start to examine how these primary colours mix to create other colours. As we mix these colours, we can see why these colour wheels are laid out the way they are. Take a look at the two sets of colour wheels below to see what I mean.
Click to enlarge. Now, we're starting to get a clearer idea of why the two wheels are laid out differently. The secondary colours are between the primary colours, as we see here.
You should see that secondary colours are simply the colours that sit between the primary colours on each wheel. So, although both colour wheels appear to have a red and a blue in common for their primaries, the secondary colours are clearly quite different.
There is a very reasonable scientific reason for why we have two colour wheels and how reflected light and transmissive light of subtractive colours and additive colours, respectively, vibrate at different wavelengths to create varying colour combinations... but this article is long enough already. I aim to create an article specifically targeted at photographers and what we NEED to know but if you're interested in the deeper-dive physics of this topic, then I recommend this linked article for some light bedtime reading (see what I did there) on Light Absorption, Reflection and Transmission. Enjoy :)
Complimentary Colours
Now, let's take the principles we've learned about what 'white' light actually is and apply a little colour theory to it. In art, we have something called colour theory. This is the principle that certain colour combinations are more favourable and resonate well with us as people than other colour combinations. One of the most popular colour theories is the one we refer to as 'complementary colours', and we'll be exploring this a little deeper with coloured light here.
If you have a colour wheel, complimentary colours are very easy to understand as a complimentary colour is simply any colour that is opposite one another on the colour wheel.
These three complementary colour combinations—yellow + purple, red + green, and blue + orange —are certainly the most popular, but is there a reason for that?
Take a look at the colour wheels above, and you'll see the examples of complementary colours that I've pointed out. These three colour combinations are certainly the most popular: red and green, purple and yellow, and orange and blue. But is there a reason for that?
These complimentary colour combos are so popular because they each contain a primary and a secondary colour. If you're a bit rusty on your primaries and secondaries, take a look at my handy image below to refresh your memory.
Click to enlarge
Now, let's take a look at how those secondary colours are created by mixing two primary colours.
Blue & Yellow = Green
Yellow & Red = Orange
Red & Blue = Violet
The primary colours and the secondary colours - Mixing primaries will result in secondary colours.
It stands to reason that colours that are essentially derivatives of their primary brothers actually become their complementary counterparts.
For example, yellow and purple are complementary colours. The other two primaries that aren't yellow are red and blue. Mix those together, and you get purple, which is complementary to yellow.
JEEZ JAKE! I normally only come here for the pretty pictures of ladies covered in oil and coloured lighting!!! This is a bit much!
Yes, I do apologise if this is a bit of a headache, but you really don't need to know the math behind colour theory to be good with it. However, it certainly can be nice to know how it all ties together. Here's a quick list of the complementary colours and how they relate to their primaries.
Complimentary colours are simply primary colours and a combination of their brother's primary colours. For example the complimentary colours yellow and purple are yellow plus the other two primaries combined, red and blue.
So, although you don't need to fully understand the reasoning behind how certain complimentary colours are made, you do need to know how important they are.
Everything from room decor to corporate branding, from the clothes we choose to wear to the packaging we're drawn to on the shelves, undergoes colour theory before it's released.
I cannot overstate how powerful colour is in our everyday lives, so it stands to reason that colour theory is incredibly important, too.
The biggest distinction about colour theory so far is that it uses the painter's wheel to figure out harmonies in colour. Do not use the lighting colour wheel to work out what colours work well together; that is purely used to show how certain coloured lights will mix to generate other coloured lights.
Mixing Complimentary Colours with Coloured Paint
In the previous section, I explained the importance of complementary colours and how powerful the colour theory behind them is. Before we talk about using complementary colours in lighting, I just wanted to quickly show you what happens when we mix complementary colours with paint.
I doubt the resulting images below will surprise anybody. Paint mixes the same way physical colours have always done, and the resulting colours are the same now as they were when we were crushing up beetle shells and mixing them with fern roots. The important thing here is how different this is from mixing complementary colours in lighting.
Yes, when I use the term brown to describe the resulting colours above, I'm generalising greatly, as there are many different versions of brown. But let me explain how the colour theory of paint works when it comes to mixing colours.
When you mix primary colours (red/yellow/blue) you get the secondary colors (orange/green/purple). When you mix the primary colors with the secondary colours or use different amounts of primary colors, like if you have more yellow than blue, you get all the other shades in the color wheel like yellow-green, blue-green, red-orange, yellow-orange, blue-purple, red-purple, and so on.
When you mix two complementary colours like purple and yellow, you simply get a shade of 'brown'. The brown isn't important, but what is important is how we get a very different result when we mix complementary colours in lighting.
Mixing Complimentary Coloured Light
Okay, so now let's apply the test to our photography world and see how colours mix when using light compared to paint. First, let's see what happens when we mix the lighting primary colours of Red, Green, and Blue. This will give us a baseline of how light mixes compared to paint and will also show us why the RGB colour wheel is laid out the way it is to create its secondary colours of Magenta, Yellow, and Cyan.
Thankfully, this test was fairly simple. All I did was attach coloured gels to the ends of two gridded strobes, fire them against a white wall, and take shots of the colours separated and another couple of shots of the colours mixed.
Click to enlarge Above, you can clearly see how the coloured light mixes on a white wall. Red and Blue make Magenta, Red and Green make Yellow, and Green and Blue make Cyan.
The results above speak for themselves. Although I was aware of the principle of mixing coloured light before I did this test, I was still pretty surprised at how well these coloured lights actually mixed on a wall. Remember, the lighting colour wheel is based on mixing transmissive colours, colours that mix as they are emitted from a screen and not shone onto a surface.
The next stage was to test how the complementary coloured lights mixed. The results were very different and, honestly, pretty surprising.
Click to enlarge This is the result of mixing the complimentary colours together; purple & yellow, red & green and orange & blue.
What's interesting about these results is why it is so important for us to employ clean lighting when using coloured gels. Thankfully, red and green are two of our primary colours on the lighting colour wheel, so mixing those two coloured lights produced the expected results of yellow, but it's when we mixed the other two complementary colour combinations that it got interesting.
Mixing both violet & yellow and orange & blue actually produces grey.
It's probably more technically correct to say that these colours cancel each other out, but essentially, mixing these two complementary-coloured lights together removes their colour, leaving a dull white colour in its place.
Colour Banding…. or Bad Lighting?
So, you made it this far, and we can at last discuss this 'colour-banding' problem that I'm sure we've all faced at some point.
What is colour banding? Colour banding is the odd 'stepping' of colour that can be produced in very saturated images. It is when colour doesn't smoothly transition from one colour to another in our digital images. In the image below, you should see that the colour on the model's arm goes from orange to grey and then to blue, and this look is often referred to (sometimes mistakenly) as colour banding.
Now, technically speaking, this example isn't strictly colour banding, but for the sake of argument, we're going discuss what causes this effect and how to avoid it.
This infuriatingly ugly effect is a huge problem with coloured gelled lighting, and for years, I thought it was simply crappy digital cameras not having the power to render all the colours I wanted or even online platform compressing my files which resulted in this ugly visual stepping effect, and although this certainly plays a part, it would seem we can only blame our tools so much.
Click to enlarge The image above clearly shows what I mean by colour banding but take a closer look. Is it actually colour banding or is it messy lighting?
The above raw image clearly illustrates what looks like colour banding, but in actuality, it's not the camera's fault; in fact, it's messy lighting.
What is happening here is that two complementary colours meet on the skin, and when they do, they appear grey as they cancel each other out. Look closely at the circled section above, and you'll see that the colour on the arm goes from blue to grey to orange—not a pretty look. Remember what happened in our lighting test earlier when we mixed complementary coloured lighting? Does it look familiar?
So how can we avoid this? Well, the simple answer is first to be very aware of what happens when you mix certain coloured lights together in a scene. The biggest offenders (and likely the ones you'll be mixing the most) are the complimentary colours. Thankfully, red and green only produce yellow, which, although unlikely to be a good thing, is still better than grey, and of course, the biggest culprits are the mixing of orange & blue plus the purple & yellow creating grey. This unsightly gelled lighting phenomenon is certainly something you want to avoid at all costs, and thankfully, you can do just that with proper light control as we see below.
Click to enlarge Colour banding can be avoided with proper light control but more importantly so can the ugly grey overlap of complimentary colours.
All of the images above show heavy use of the complementary colours orange and blue, but you should see that I've avoided the dreaded grey colour overlap that can occur when combining these lights by keeping the lighting clean and never spilling the two colours onto one another.
Now, I understand that this is a lot easier said than done, and actually keeping the lighting separate is the topic for another article. Still, I hope you can see how important clean lighting is now, especially with colour gels.
Closing comments and conclusions
Firstly, thank you if you've made it this far in the article. I'm not known for my short, snappy social media posts or articles, and this monster of a piece is no different. But I do feel that everything being said here is relevant and although I debated splitting this up and getting multiple posts out of it, I really think everything here needs to be seen together to fully understand what is going on.
Although I didn't want to complicate this any further, I will add that we, as photographers, actually operate between the two colour wheels. Don't panic; what you've read so far is relevant, but we, as artists who use light as our medium, fall between the two colour wheels because the lighting colour wheel is for transmissive RGB displays only. Yes, we use light, but we shine that light onto an object and then photograph that reflected light, and reflected light is what painters use to mix colour. I know that is a bit of a mind-bender, but really, all you need to know is that light mixes like it does with RGB, but bear in mind that it requires a white surface to be the subject for it to remain relatively accurate. Chances are you're not photographing coloured gels on white walls, so caution is required when making assumptions about the mixing of colour on another surface that has its own colour, like skin. Like I said, I didn't want to overcomplicate something that was already fairly complicated, but I wanted to highlight that point to any of you who may have been wondering about it.
Points to remember
Use the painter's (subtractive) wheel for colour theory. For example, use it to work out complementary colours.
Use the lighting (additive) wheel to work out what coloured lights to mix, or what will happen if you do mix certain coloured lights together.
The more paint you mix together, the darker the colour will become. The more lights you mix together, the lighter the colour will become.
Complimentary colours are always opposite one another on the painter’s wheel. For example, orange and blue.
Mixing two of the three primary colours will result in a secondary colour for both the painters and the lighting colour wheels.
Mixing certain complementary coloured lights will result in grey, such as orange and blue or purple and yellow.
Always try to keep the coloured lights separate on whatever you're photographing. Failure to do so will result in an ugly-looking colour banding effect.
For reference, print out or save these 'cheat sheets' below on how colour theory works.
Click to enlarge. The painters colour wheel theory
Click to enlarge. This is the difference between mixing paint and mixing light
Click to enlarge. How complimentary colours are created
Click to enlarge. The two colour wheels you must understand and why
For more of these cheat-sheets, head over to my Quick-Tips page that has loads more of them on all kinds of photographic topics.
I know this was a monster-brain-melting article, but I've seen very little on this topic that is specifically targeted at us photographers, so I hope it helps at least one person understand more clearly what's going on when mixing coloured gels.
As always, thank you, and if you have any questions or anything to add, feel free to keep it to yourself.......sorry, I meant post it in the comments below ;)
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LAST 2017 WORKSHOP DATES ANNOUNCED - If you're interested in any of my work and would like to know more about how I created some of my shots then why not check out my workshops. Here you can find out everything there is to know about Gelled Lighting, Long Exposure Flash Photography and my entire Post-Pro Workflow. Jake Hicks Photography - Workshops
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