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A flash gel is a lighting filter for your flash: clear heat resistant polyester sheets that are placed between a light source and the subject being lit. In the same way that we might use glass filters for your lens, we use plastic gels for a light source.

Lee flash gels, which fix over the flash head with a strip of velcro. A reasonable option for creating coloured backgrounds - about £10

Studio Backgrounds

Flash gels have quite a limited use in extreme macro as we don't tend to colour our subjects with coloured lights, but they are nevertheless a reasonable option for creating coloured backgrounds.

The clean white and seamless background has become the standard for model portfolios, fashion, portraiture and product photography to keep all the attention on the subject. For most jobs, all that is called for is a plain white or a neutral light grey that can be over-exposed and thus made to appear pure white.

Gels for Colour

Remember, there is a loss of light intensity when using gels

This is where gels come in handy. Rather than change the actual background paper, you can instead change the colour you light the white background it with. Clip a coloured gel over a flash and use as a background light. Our white background can thus be changed to appear green, purple, blue: in fact any colour that we have a gel for.

We can even use two flashes to get blended colours and other effects: far cheaper and more versatile than to keep swapping the background itself. The main foreground flash will remain neutral so the specimen will still be lit correctly, and directional backlights can be used to outline the specimen and separate it from the colour behind.

Gels in Use

a reasonable option for creating coloured backgroundsRemember, there is a loss of light intensity when using gels. With deep colours, heavy correction or dense diffusion, the loss can be appreciable. You can also be more creative with gels by covering only a portion of the light beam with colour, diffusion or ND.

Small strips of hobbyist gels are available through eBay which come with velcro studs to attach them to your flash. They are under £10 and are considered expendable. Over time, flash gels become brittle, the colours will fade, and the degree of correction will change.

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