Tuesday, May 18, 2010

Balancing Flash and Ambient Light - Part 2: Sunny Outdoors (Easy Way)

When taking shots outdoors while it's very sunny, you will likely have to deal with harsh shadows, which are not always flattering.  One solution in such a situation is to use flash.  The technical challenge though is that in order for your flash to act as a key light, it must be brighter than the sunlight, which is not easy for small flashes, and even harder when using a light modifier.  The easy way to balance flash and ambient in such a situation is to find a shaded area for your subject.  This will then be similar to the easiest scenario for mixing flash and ambient.

In the shot above, we were visiting the Griffith Observatory and it was quite sunny.  Fortunately there was a shaded spot from the monument in front of the observatory.  In the shade, it was possible for my little SB-800 with a propet handheld umbrella to act as key light.  Steps:
1. Position subject in the shade.
2. With the flash off, set exposure for the sunlit background (or allow slight underexposure if you want to emphasize the subject -- but this will require more power from your flash).
- I used manual exposure for maximum control.
- Metering mode was matrix. This allows the flash to function in i-TTL BL mode (which tries to balance the flash exposure with the ambient exposure)
- I set the ISO to the base ISO of 200 for the D300.
- I set shutter speed to the sync speed 1/250.
- I set aperture so that the light meter was at 0.  With a circular polarizer attached (for a bluer sky), aperture was at f/7.1.
- I took a test shot. Background looked ok.

3. I took a shot with the flash, aiming the flash in the same direction as the ambient light.
- I raised the popup flash to get ready to use it as a commander.
- I switched the flash to commander mode using the camera's menus.
- Because the subject is in shadow, the ambient light within the shaded area acts as natural fill, so I set the popup flash to inactive (it will only act as commander - it will not contribute light).
- I set the remote flash on TTL.
- My SB800 was mounted on a propet umbrella as a modifier.  I aimed it in the same direction as the ambient light.
- I took a shot.  If it looks ok then you're done. 

4. Adjust TTL as necessary.
- I felt the flash exposure was too high. I adjusted to -0.7 FEC. This became the final shot. (In post processing, I reduced contrast slightly, cropped slightly, and straightened the picture).

From Maty 33+ Months