Tuesday, April 6, 2010
The Balancing Act Of Flash On Location
Building and mastering the art of mobile lighting will give you the tools to shoot anywhere
For my travel magazine and reportage work—especially in places like North Korea, Iran and Myanmar—I’m a one-man band. That means traveling light and low-key. My key to using flash is subtlety. In general, I want it to positively affect my photography without the image screaming, “FLASH!” While some fashion photographers want that “paparazzi” look, it’s not for me.
Lastolite Triflash Bracket
One of my favorite techniques is a combination of a long exposure with multiple pops from a single flash. To illuminate two statues hidden in the recesses of a stupa (a kind of pagoda) in Bagan, Myanmar, I fired two flashes from my Speedlight SB-800 during a 20-second exposure. I approximated the same value as the large Buddha that was illuminated by sunlight. After locking down my Nikon D3 with a Nikkor 14-24mm ƒ/2.8 on a tripod, I set the camera to timer. An aperture of ƒ/16 not only gave me great depth of field, but also gave a long enough exposure time to run from one statue to the other without being recorded by the sensor. I taped a 1⁄8 CTO (color temperature orange) over the flash head to slightly warm up the cool daylight-balanced flash. This last part, color balance, is vital for a realistic look.
Mixed Sources And Color Temperature
While we can use presets, such as sunny, cloudy or tungsten, and adjust white-balance values in Kelvin (on professional cameras), as well as shoot RAW and adjust color, none of these will correct a color imbalance if the image has mixed light sources, e.g., tungsten and daylight. Processing a RAW file twice, then putting the images together, requires time and effort, which I’d rather use creating imagery rather than “saving it” in post. It’s better to get it right on the initial capture.
A basic understanding of the Kelvin scale will aid in this endeavor. The scale was named after the Irish-born physicist, mathematician and engineer William Thomson (Lord Kelvin), who was instrumental in the development of an “absolute thermometric scale” in the mid-19th century.
Basically, higher color temperatures (5000 K or more) are cool (bluish-white) colors. Lower color temperatures are warm (yellowish-white through orange to red). Daylight film emulsions are calibrated to approximately 5600 K, as are the daylight settings on our digital cameras.
When I was starting my career shooting stills on The Merv Griffin Show, I shot with tungsten-balanced film with a 3200 K temperature to balance to the studio’s hotlights. These days, a quick adjustment of the white-balance button to the tungsten setting on a digital camera is all it takes. Fluorescent lamps emit light primarily by a process other than thermal radiation so it doesn’t follow the Kelvin scale, which is based on thermal radiation. Instead, these types of light sources are assigned a CCT (correlated color temperature). Fortunately, we have presets, filters and gels to remove these unattractive colors from our images.
Page 2 of 5