 BetterPhoto Member |
Bouncing Flash with TTL When using bounce flash on my on-camera TTL unit, by how many stops do I need to increase the lens aperture? How do I figure this out?
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John A. Lind |
Donna, If you are operating the flash/camera in "TTL Auto" mode and the camera controls how much flash output there is using its TTL metering sensor(s), then there is no requirement to increase the lens aperture. The camera will automatically increase the flash output to obtain the required amount of light. Same thing applies if you are operating using an "Auto" mode on the flash with the light sensor on the flash, provided the sensor on the flash is not tilted, just the upper part of the head. All that said, bounce does require more light from the flash. If you are already working at over half the flash range for direct lighting and the aperture you are using, the flash may not be able to supply enough light. In this situation, open up the aperture a stop. The light loss is typically at least a stop and sometimes two. It depends on distance to the wall or ceiling you are using for bounce, and how reflective that surface is. There are a lot of variables here. For these reasons, I recommend using bounce in an Auto mode of some type . . . whether it's a "dedicated" TTL Auto mode with your camera controlling the flash, or the Auto mode using a built-in sensor on the flash itself. -- John
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