Off Camera Flash

June 20, 2007
 

For these photos, I was photographing on location in buildings I had never seen before the day of the session. In planning what to bring, I wanted lighting that was relatively portable and quick to move (not heavy, no electrical cords). I also wanted to use the camera hand-held and be able to move easily from one area to another (no tripod which means no slow shutter speeds).

Model and green door Canon 5D, 24-105mm f/4 L lens at 35mm ISO 400, 1/80 sec, f/8 1/80 second used here because this area was darker

Equipment

The equipment was simple: Canon DSLR, zoom lens, light stand, 45" silver umbrella with a black backing, umbrella mount for the light stand, 2 Nikon SB-800 flash units and a Bogen Justin clamp. One SB-800 was mounted on the camera's hot shoe (actually, it was mounted on a flash bracket connected via a flash cable to the hot shoe) and the other was pointed at the inside of the umbrella, bouncing light towards the subject. This SB-800 was attached to the light stand with a Justin clamp. The SB-800 could also have been on the umbrella mount but I find that is not as secure. I can also quickly take the clamp off the stand, with the SB-800 still mounted, for carrying.

Since the camera and flash units were from different companies, I set both the camera and the flash units to manual modes. Most, if not all, DSLR companies offer flash units that will communicate wirelessly to make off-camera flash usage a simpler task. But you can do it all yourself with any flash unit with a few more steps. About the only requirement is that the flash must have a manual mode where you can vary the output level. The SB-800s let me vary the output level from full to 1/128th power.

Process

The flash on the camera is used mainly to trigger the flash on the light stand. I don't want the flash on the camera (the master or controlling unit) adding much light to the subject. So I had the on-camera flash set to the lowest output level. The other flash, the remote unit, is set to whatever I need for my conditions. For the photos that day, I used an ISO of 400 and an aperture of f/8. This meant the flash unit was usually at full or 1/2 power (sometimes 1/4).

The initial process was as follows. After that, I only needed to tweak the remote flash output level when the distance between the light and the subject changed.

1. Set light where you want it and flash output to full.
2. Set camera to manual and a shutter speed between 1/60 and 1/200 second. If the shutter speed is higher, part of your photo may be dark because the shutter opening and the flash are not completely in sync. Slower than 1/60 second and you may have a color or light halo around your subject due to camera or subject movement.
3. Set aperture to what you want.
4. Set ISO to a low value.
5. Take a test photo and check your histogram. If too dark, increase ISO or make your aperture larger. If too bright, decrease ISO or make your aperture smaller or reduce output level on the flash. Repeat if necessary.
6. Once your subject is properly lit, check how the ambient light is recorded. Your shutter speed controls this. If you find the ambient light to bright, make your shutter speed faster. If the ambient light is too dark, make your shutter speed slower. Just remember the range of 1/60 to 1/200 second.

Model and vending machine Canon 5D, 24-105mm f/4 L lens at 28mm ISO 400, 1/160 sec, f/8

In the photo above there is a large open door, sizable enough for a truck to drive through, to camera left. The day was lightly overcast so a lot of indirect light is coming into the warehouse. I wanted a darker ambient light which I got by using a shutter speed of 1/160 second. The subjects, the model and the vending machine, are lit by the remote flash unit bounced into the umbrella, positioned to the left of the camera. My aperture of f/8 gives me the depth of field I want and an ISO of 400 makes it all work. That ISO also keeps my shutter speed below 1/200 second.

Downsides

This setup has a few downsides. The remote flash units must have their photo sensor positioned so that light from the master unit can be seen by the remote unit. This is essentially a line-of-sight configuration. There is also a limit on how far the remote units can be from the master. Wireless radio transmitters, such as Pocket-Wizards, get around this problem. The flash units also fare poorly or are useless in bright lighting conditions such as direct sunlight. The flash units simply don't have enough power to 'outshine' the sun. For that you need more powerful strobe units which usually means access to electricity or using a portable power generator. Now you are carting more and heavier equipment to your location.

In general, I find portable battery-powered flash units work well indoors or outdoors in considerable shade or during early morning or late evening when sunlight is not as powerful.