Using Gels to Change Background

Do you have an off camera flash?
Can you trigger it using a remote or the pop-up flash on the camera?
Do you only have a single background colour?

If the answer is yes then this may be the post for you.

Did you know you can change the colour of your background without having to invest in expensive back drops or repainting your wall.

By using colour gels in front of your flash you can transform the dull grey, black or white background into a radiant blue or red and if you have multiple flashes you could have multi-coloured backgrounds.

What are Gels?

Gels or filters are transparent coloured sheets that are placed in front of the flash to change the light that is emitted also known as Colour Correction Gels. The main colour correction gels are CTB (colour temperature blue) and CTO (colour temperature orange). A CTB gel converts tungsten light to ‘daylight’ colour. A CTO gel does the opposite.

How do we change the background

First of all you will need a stand to put your flash on, or use the small foot stand that came with the flash and something to stand it on. I will assume you may not have a light meter or a great deal of space.

You will need a way of triggering the flash, so a remote, the pop up flash on your camera or a long trigger cable.

Lets start by putting the flash to manual, and if it has a zoom, setting this to its widest (all flashes are different so please read the manual that came with it). Set the flash to half power and place about 3 – 4 feet away from the background. Depending on the type of image you are doing, if a head shot then place flash height to about the center of the model’s head, if the top half then center of the back as a general rule.

Above Grey background and Grey background with flash firing with red gel.

Now this bit depends on how you shoot your images and assuming that you have more than one flash, one to light the background and another for the subject.

Setting up to light the model

First is to eliminate all the ambient light, ( not shooting with the lights off ). What I mean by this, is to set the shutter speed to the maximum sync speed of the flash and then adjust the aperture, ( F5.6 – F8.0 usually works for me ), so that without the flash the image is black or underexposed and then turn the flash on and then adjust flash output to light the model using a light meter if you have one, or just adjust the flash output manually and take test shots.

Once this is done turn off the flash lighting the model, and turn on the flash that is lighting the background with the Gel. Take a test shot to get the intensity of the colour you want. Turn both flashes on and shoot away. The background will always be the colour you want and the model should be perfectly lit.

The above is one with standard grey background and three coloured Gels.

What if you only have one flash?

If you only have one flash then use natural light, like a window for lighting the model and try and stop too much light hitting your background. Then expose for the model and then adjust the flash lighting to the background accordingly. You may need a higher ISO to keep the camera settings the same and the output on the flash may need to be stronger, so make sure you have some spare batteries.

More than one flash

If you have two or more flashes then try gelling two with different colours and put them out to the side and point them into the center to create multi-colour backgrounds.

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