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

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.

With our camera balanced to daylight and using a tungsten light source, our professional model looks like he should be in TOWIE..

..so by applying FULL CTB the skin tone looks a bit more natural now.

If your subject has a lighter skin tone or if your camera’s auto white balance reads around the 4500K mark (for some fluorescent lighting), you may want something in the middle between tungsten and daylight and HALF CTB may be your answer, converting tungsten sources to 4300K. In this shot the camera is still balanced to daylight.

• CTO

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.

Using a daylight balanced LED light and with the camera balanced to tungsten, our image is looking a bit cold. But there is a use for this though; it is a popular method of simulating moonlight as well as shooting ‘day for night’.

But if moonlight isn’t what you’re after, FULL CTO will return the skin tone back to a more natural colour.

HALF CTO converts 5200K to 3800K, so a little cooler than FULL CTO but not too far off. With the light I’m using (dedolight ledzilla) and the model’s skin tone in this case HALF CTO actually looks a little nicer.

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

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.

Oh no, you can see that I forgot to iron my backdrop..so in this shot as you can see our model is looking a bit ghostly. Time to crack out the ND.

ND.3 reduces the light by 1 stop.

ND.6 reduces the light by 2 stops.

And ND.9 reduces the light by 3 stops.

Wise words a gaffer once said to me, “you can never have enough ND!”

• Diffusion

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.

Our professional hand model is currently being lit with a hard LED source (Dedolight Ledzilla) and no diffusion.

This diffusion used here is HAMPSHIRE FROST. Notice a subtle softening of the shadow.

HEAVY DIFFUSION is being used here (and it’s easy to see why it got this name)

I don’t actually know what this diffusion is called but it somehow found its way into my kit. A thicker, rougher sheet that is a little closer to greaseproof paper. As you can see it has a lovely texture to it and can add a bit of spice to a background.

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:

HALF DIFFUSION attached to the light..

..and the HALF DIFFUSION moved away from the light source (closer to the subject). Notice how much softer the shadow is now.

• “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.

STEEL GREEN with the camera balanced to tungsten. Sci fi!

STEEL GREEN but with the camera balanced to daylight. Lord of the Rings or Matrix?

More subtle than the above, a STRAW lighting gel with the camera balanced to tungsten. A nice morning light look.

A STRAW gel but with the camera balanced to daylight. I’m getting a CSI Miami vibe here.

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!

Experimenting is key to finding lighting styles that will grab your audience’s attention.

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.

Happy shooting!

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.