ever area the flash doesn’t illuminate will turn some shade of blue, depending
on the amount of ambient light. For example, if I place a model outside under
open shade, then place a^3 / 4 CTO on my flash and set my white balance to
3200K and depress the shutter button, the flash will fire and illuminate my
subject. My subject will look as she should when illuminated by a tungsten
source, but the background and sometimes the foreground will turn blue if it’s
illuminated with daylight or a daylight-balanced light source.
Because I prefer to shoot warmer tones when photographing models, I
often “bump up” the warmth by setting my camera between 3700 and 4000K
(the amount of the adjustment depends on each model’s skin tone) instead of
the normal 3200K. With this technique, my camera doesn’t know if I’m using
flash or a flash covered with a CTO, it only knows what I tell it from the set-
tings I set. In this case, I’m using the 3700–4000K setting to trick the camera
into thinking the light source is slightly cooler than tungsten. Therefore, the
camera will add more warmth than would be the case if the white balance was
set to 3200K.
Now let’s pretend I want to make the sky red, not blue. I simply tape a
Rosco cyan (opposite of red) gel over my flash, then have my subject hold a
white 100 IRE card (some camera manufacturers prefer an 18 percent gray
card) while I photograph the card with the cyan-gelled flash. (Note:If you
don’t have a 100 IRE white card available, a white t-shirt or white towel will
work.) The key here is to fill the entire frame with the white card or white ob-
ject, store the image in the camera, and select it as your white bal-
ance image—a custom white balance. Most cameras have their own
proprietary method for setting a custom white balance, so please
refer to your camera manual.
When I photograph my subject with cyan-gelled flash and use
the custom white balance I’ve just set, the subject is illuminated
with cyan light, but the camera adds red to ensure a known white will remain
white with that light source. In this case, then, the background will turn red
and the subject will be rendered with a normal skin tone.
Please keep in mind, the custom white balance method over the manual
white balance method is not always an exact science. With the^3 / 4 CTO over a
flash unit, you can easily select the exact number (3200–4000K) as the^3 / 4
CTO is an exact science when used in conjunction with on-camera or studio
flash (5000–6000K). Unfortunately today, with the more complex gels (cyan,
magenta, red, etc.), you must do a custom, not manual, white balance. While
most cameras can handle this well, some only come close. When using these
colored gels, it’s best to capture your images in the RAW (or highest-quality
70 LIGHTING FOR GLAMOUR PHOTOGRAPHY
If you don’t have a 100 IRE
white card available, a white
t-shirt or white towel will work.