USE A VARI-ND FILTERWhat if you want to control the ambient light and underexpose it, but you don't have HSS or HyperSync available? Another way to darken the daylight exposure is by using a Vari-ND filter. These filters work by reducing the light evenly as you rotate the filter. I use a Singh-Ray Vari-ND. This filter reduces light from two to eight stops, easily underexposing even a sunny midday scene. A polarizer also could be used to reduce light, but they generally only reduce one to two stops of light.
But here's the trick if you're using flash in this image. The daylight exposure will be reduced, but so will any flash added to the shot. Expect to really increase your flash exposure to counter the Vari-ND's effect. If you're only reducing the ambient exposure by one to two stops, then your speedlight or studio flash system shouldn't have much trouble adding enough light. This allows you to underexpose the ambient exposure another one to two stops if you want a dark background for your shot.
Sometimes this can be taken to the extreme. I did a fly-fishing shoot where we wanted the river water to be silky, flowing around a fisherman in the river. Since we were shooting in bright sun, I used a Vari-ND filter to get the 20-second exposure needed for the silky water. But since I reduced the light by six stops, my 1,100W pack couldn't produce enough power to light the fisherman, even shooting multiple full-power flash pops during the 20-second exposure. To solve this problem, I did a double exposure. My first exposure was with the Vari-ND attached to create the silky water at 20 seconds. For the second exposure, I took off the Vari-ND and shot one flash burst on my fisherman. The final shot had silky water and a lit fisherman.
LIGHT THROUGH A CUCOLORISMany assignments I get involve shooting a quick portrait of an employee in an office setting. Businesspeople need headshots, and brochures need images of employees. These companies want a great shot, but give you 10 minutes and a tiny office as your "studio." One challenge of these small interiors is controlling the flash, but grids work well here. Another challenge is the stale, boring walls most offices have. If only there was a quick way to liven up those white walls. Enter the cucoloris.
The cucoloris is a plate with holes cut in it for the flash to shoot through. Also known as a cookie, it can have a variety of cutouts, from venetian-blind bands to random holes. When a flash is shot through these cutouts aimed at a blank wall, interesting patterns and shapes are created. Shoot your flash through an orange gel and a cucoloris aimed at a white wall, and watch the effect. Instead of a boring white background, you create "sunlight filtering through tree branches" on the wall.
If you're the do-it-yourself type, buy some Rosco Black Cinefoil from your photo store. Cut out a 4x6-inch piece, poke interesting holes in it, and shoot your flash through this to produce patterns on the wall. I use the Lastolite Strobo Kit for this effect; it has metal plates with different cutouts, and a simple attachment system for both speedlight and cucoloris. This kit also allows you to put a gel in front of the cutout to change the color of the flash.