Gels are used by cinematographers and videographers to balance the colour of light sources, adjust contrast and control shadows. It is the use of these gels that helps to create certain moods and looks to productions, whether that be low key drama or high key corporate video.
If you don’t know your ND from your CTB then read on as I introduce some of the most popular lighting gels and demonstrate how they may be used in your productions for creative effect.
CTB (not to be confused with CBT!) stands for colour temperature blue and is often referred to simply as ‘daylight’. It is used to convert tungsten balanced light sources such as traditional household bulbs and fresnels from 3200K to 5600K. It’s a common gel for balancing artificial light sources to daylight when the sun is acting as the key light in a scene.
Another popular colour correction gel is CTO which stands for colour temperature orange and is often simply referred to as ‘Tungsten’. It is used to convert daylight 5600K sources to 3200K, in line with the colour temperature of most traditional household lamps.
Both CTB and CTO also come in other strengths including QUARTER and EIGHTH, for those more subtle differences, but FULL and HALF are the most widely used.
ND stands for neutral density and is used to reduce the amount of light without altering the colour. ND is often used on the camera in filter form but for lighting it can be invaluable in helping to control exposure and contrast. Using ND to reduce powerful light sources that do not have dimmers (or if you don’t want to change the colour temperature of the source through dimming) or stopping natural light from washing a scene out through covering windows with these gels, it is an incredibly useful tool.
Wise words a gaffer once said to me, “you can never have enough ND!”
Diffusion is used to control the softness of shadows and the softer the source the less prominent the shadows will be. As hard lights have typically much higher output than soft lights, diffusion is key to softening these sources whilst utilising a strong beam.
There are so many different types of diffusion available and it can be difficult to know where to start so here are a few examples to give you an idea of the range available. At the end of the day it’s down to you to experiment with various types and find what you like.
It’s important to note too that the further a piece of diffusion is away from a light source, the softer the shadows will be, as will be a slight reduction in overall output of the light. See the example below:
- “Party” gels
Not necessarily an official term but in this case I shall refer to most other coloured gels as ‘party gels’. Whilst these may not be as important for most shoots as the colour correction and other gels mentioned above, they can be used to create certain moods for your scenes whether they are used as key lights, backlights or kickers. There are an almost endless number of these gels to choose from but here are a couple of examples.
So, which gels should you buy?
It all starts with the light source(s) that you’ll be using most. Their colour temperature, power, whether they are dimmable and how hard or soft they are will all determine the gels you need. Aspiring DOPs will probably accumulate gels over time as their portfolio grows, but a good place to start is with the simple colour correction gels (CTO and/or CTB) and some diffusion which are the bare bones for lighting anything professionally. Another thing, don’t always rely on kit hire companies to stock a wide range of gels!
Part of the fun and the craft of being a DOP is finding lighting styles that fit your productions and consequently help you to create your own signature style. Experiment with gels and see which colour combinations work and which don’t. Get creative!
Whether you are new to lighting or not, the LEE filter comparison tool here is a fantastic resource to see the range of lighting gels available and help you make decisions on what to buy. LEE filters are widely considered the number one name for gels; heat proof, colour accurate and with a huge choice available, they are an essential investment if you’re an aspiring DOP.
P.S. This post would not have been possible without my trusty light meter. Here are a few reasons why every aspiring DOP simply must have one.