Flash white balance settings

[administrator]

What white balance setting should you use during flash photography?

Well, here's the easy answer:

Use the "flash" pre-set button on you camera. If you use the built in flash or a flash made from by the same company that manufactured you camera, you should get a pretty good match between the actual color temperature of the light from the flash and the color temperature preset that is programmed into the camera when you select "flash" from your white balance menu.

Here's the more complicated answer:

Flash light color temperature is approximately 5000 to 7000 degrees Kelvin. I have seen actual measurements of Canon EOS flash units where the data showed a range of 5100 to 5750, and various posts around the internets cite a flash color temperature of 6200 to 6800 (on photo.net) and 5500 to 6500 (explore-photography.com) and 4800 - 5500 (corporatefinart.com)

To make this even more fun (or confusing - depending on your interest in the details), the color temperature of a given flash unit will vary based on the power output selected by the metering system and charge state of the capacitors that are storing the electrical charge for the flash. I have seen data from a Canon 550 EX flash showing a range of 5100 to 5800 degrees Kelvin. As the flash power was reduced, the color temperature of the light increased.

These same data showed that there was as much as a 450 degree difference depending on capacitor charge state. For example, the color temperature increased progressively from when the green ready light came on (minimal charge necessary for flash) to when the red light came on, and continued to increase until the capacitors were at their maximal charge. So, the flash color temperature you get will depend on how long you allow your flash to recharge between shots.

So given that flashes vary between brands and models, and given variations in in battery charge states and flash output power, what is a photographer to do?

1) Shoot RAW and include a Digital Grey Kard in the photograph. The card will allow you to adjust the color temperature easily, accurately and quickly in you post-processing software, such as Photoshop Lightroom.

2) Take a flash photograph of the Digital Grey Kard and then use the flash photograph to set the custom white balance function. Make sure the white balance shot is shot under conditions that are similar to your actual flash power settings you wiol be using. Also, use the most stable power source available for your flash to avoid variations, and allow your flash to recharge approximately the same amount of time between each shot, if possible.

3) Use one of the new flash units (such as the Canon 580 EX II) with a compatible camera body (such as the Canon 5Dm2) where the flash sends actual color temperature values to the camera immediately after the flash fires.