How to use Flash Gels
Despite their name, flash gels are rarely anything like what most of us would think of when we hear the word “gel”. They are not soggy or used for holding your hair in place for one thing! Flash gels are more often than not made from plastic. If you have ever bought a flashgun (speedlight) then you will probably have received a couple of flash gels with it. These are clip-on pieces of plastic that are normally orange or green. Or, you may have seen theatre lighting when they have transparent coloured sheets over the lights to produce coloured spots on the stage. They are light modifiers that enable you to refine the colour of your flash. So, let’s take a look at how to use flash gels in various types of photography.
I like to use splashes of colour in my fashion photography at times. Whether in the studio or outdoors, you can point a flashgun at a surface behind your model to create a pool of coloured light. In the examples above I have used a blue flash gel inside a gridded snoot to keep the light controlled and focussed. The first image was taken at night outside an old church. The second image was taken in a studio against a plain black backdrop.As you can see, the effect is even more focussed and subtle in the studio shot. You can use a tighter grid to focus your light onto a very small area. The effect just lifts the image slightly, making it a little different to normal.
Another fun way of using gels in the studio is with still life photography. In the first example below I have used just the basic gels that came with my Nikon speedlights. One has the orange and the other the green plastic clipped onto the front of the flashgun. They were angled diagonally, not pointing directly at the glass. The glass itself was sitting on white acrylic inside a light tent. The second image is the same technique, this time using a blue gel instead of the green.
You can buy various different colours to play with. They are available for speedlights and large studio lights. Just make sure you get a kit that will fit your flash!
Besides adding a bit of colour to your images, flash gels also serve a very important purpose: colour correction for balancing flash with ambient light. You can normally use a flash without a coloured gel if you are just shooting with flash or if you are shooting outdoors in daylight. See my blog post on outdoor portraits using flash, for example. However, if you are doing a portrait shoot in a situation where you need flash and there is artificial light present as well, you need to pay attention to the colour of the ambient light. If you are indoors or outside at night then you will find that different artificial lights give off different colours. Some are very warm, creating an orange glow. Others, such as fluorescent tubes, may give a green hue. Here is an example of the process of correcting white balance for an outdoor night portrait:
In the first image I have used the flash without adding a coloured gel. The camera’s white balance was set to flash. If you had it set to auto then chances are it would use the flash white balance if it detected you were using flash. I had my speedlight off-camera using an umbrella to soften the light. As you can see, the background lighting is quite orange. The model looks natural, but the railings and everything else have all taken on the orange glow of the street lights. In the second image I have changed my camera’s white balance to Tungsten. This creates a more natural look for the background. The white railings are now white for a start! However, our model has turned a funny colour. In the 3rd image I added the orange flash gel to my speedlight. This meant that the light coming from my flash was roughly the same colour as the ambient light from the street lights. I kept the white balance set to Tungsten. As you can see, the result is far more natural. (Yes, I do realise these aren’t the best photos in the world, I just grabbed them quickly to illustrate the point!)
So, in some settings, flash gels are practically essential if you want to keep reasonably natural-looking colours. You may, of course, decide that you like the orange glow in the background and decide not to try and correct for it. It is all down to personal taste. However, it is useful to have the knowledge and the skills to be able to balance your flash with ambient light.
I encourage you to get your flash gels out of the box and try using them if you haven’t already done so. Try using them for white balance and also for adding splashes of colour. They bring a whole new creative dimension to your photography, both in the studio and outdoors. Hopefully this article will have given you some idea of how to use flash gels and inspire you to try your own ideas.
Why not join us on one of our night portrait photography workshops and try out some shots with gels?
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© Joe Lenton, January 2015