Lately, my SC-17 cable has been an essential part of my on-the-run portrait kit. I’ve been using a two-light set up with minimal light modifiers. I use an SB600 on a stand with a Sto-Fen Omnibounce diffuser, and an SB800 with dome diffuser, connected to the camera via the SC-17 and held just below the lens, as shown in the picture above. I dial down the SB800 by two to three stops, and use it as a commander to control the flash on the stand. So, the flash on the stand is my key light. The flash under the lens sets the floor of the exposure and provides a crisp catchlight in the eyes.
I saw this technique over at Strobist.com years ago, but did it wrong until recently. I didn’t fully comprehend that close to on-axis is not on-axis. I thought that using a shoe-mounted flash would create the same effect. WRONG. It moved the catchlight and threw nose and chin shadows that didn’t quite fit the idea of fill flash. Fill is supposed to lift shadows, not create new ones. In the studio, I’d use umbrellas and softboxes for softer lighting, but in a pinch with minimal gear, the SC-17 helps me get the job done.