It may be wonderful to be a photographer during the age of digital photography, but the principles of light haven’t changed just because film is no longer the preferred medium. Different light sources (sunlight and incandescent light, for example) render the colors in your photographs differently. Part of learning how to balance flash and ambient light is “color correcting” the light with the use of pieces of gel material covering the flash face. Your flash is not a complete unit unless you also have two basic gels, Window Green and CTO, or Color Temperature Orange.
Affixing Gels to Your Flash
Photographic gels are low-cost materials and can be purchased at most camera stores or online. Cut the gel sheets into pieces a bit larger than the face of your flash. Then, apply adhesive Velcro to the edges. Use the hook-half of the Velcro on one side and the loop-half on the other. This makes it easy to use multiple pieces, although this technique is seldom needed. Better yet, this allows you keep them on the side of the flash in one stack. Use the loop half of the Velcro on the side of the flash unit, so you can connect bounce cards or light shields to control glare.
Using Gels to Color Correct Fluorescent Light
Fluorescent light creates a pale, ghastly, seasick green hue. Without the right piece of gel on your flash, you will have images with white subjects and that awful green color cast on whatever part of the image is mostly lit by the ambient light source. You cannot fix this disaster in editing software.
As you might guess, you should attach a piece of the Window Green gel to your flash. This gel balances the color your camera records when one of your light sources is fluorescent. There can be some variation in how well the color is balanced because of the way a fluorescent fixture works. Its light is produced from a 60hz electric sine wave cycle, which means the light is not completely consistent, changing slightly during each cycle. When your camera shutter opens during this cycle will affect the exact color balance of each image.
Try this experiment to understand this principle better. Select a shutter speed between 1/60th and 1/125th, such as 1/80th or 1/100th. Then, use your burst, or continuous shooting, mode to take quickly 10 available-light test images. Your goal is to have a series of real-time photos that captures the cycle of the fluorescent fixture and the slight color shifts from photo to photo. Look at all 10 test pictures together on a computer screen or as prints to study and compare.
Now, that you have acquired this bit of information, you’ll know that your best shutter speeds are 1/60th, which is the equivalent of the entire 60hz cycle, or 1/30th, which equals two cycles. These shutter speed settings are not perfect matches, but they are much better than wasting time guessing and experimenting during a shoot. Another adjustment you can try if you still don’t like your results is to move the fluorescent setting on your camera to warmer or cooler.
Using Gels to Color Correct Tungsten Light
The same steps apply when the ambient light source is tungsten, or incandescent, light. The only difference is that you use a piece of CTO gel. Just as with fluorescent light, tungsten light is not steady or consistent. Some incandescent light bulbs will be warmer and some will reproduce red-orange light if they’ve been dimmed. Again, you may have to widen your range of acceptability because perfect color correction is not possible.
Shooting Under a Mixture of Ambient Light Sources
In many cases, an interior space is lit by a combination of ambient light sources: overhead fluorescent fixtures, table or floor lamps with tungsten bulbs and sunlight streaming through large windows. Remembering that tungsten and daylight balance much better than do fluorescent and every other light source, determine which is the stronger light and shoot according to it.
When fluorescent light dominants, but sunlight is also entering the room, close the blinds/shades/drapes and don’t include the covered window in your frame. When large windows allow the room to be lit mostly by sunlight, don’t use the fluorescent fixtures. There should be plenty of light and any subjects won’t object when you tell them that fluorescent light will render their skin green. Once you’ve balanced your camera and flash with the dominant light, you shouldn’t need to use gels.
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