To accurately use flash with some subjects, such as candles, gels are required for white balance.
Photography gels are pieces of transparent plastic that are placed on flash units to alter the quality of light they emit. This is most often used to "white balance" a light. All light has a quality called "color temperature," which is a measurement on a scale runs from red to blue. Light sources like candles have a redder color temperature, while sources like an overcast day have a bluer color temperature. Gels are used to match a flash unit to the color temperature of available light.
Instructions
1. Determine the relative color temperature of the available light. Some common sources are incandescent bulbs (yellow), fluorescent lights (light green) and overcast/clouds (light blue).
2. Select a gel that is approximately the same color as the color temperature of your available light.
3. Use a rubber band or tape to attach the gel to the flash unit so that the light shines through the gel.
4. Compose your shot and flash unit as normal and take the photo. Remove the gel when finished.
Tags: color temperature, available light, flash unit, color temperature available, sources like