Automatic E-TTL flash exposure in bright light

I’ve seen plenty of pictures where automatic flash, E-TTL, gets it wrong. Ever since I completely switched to radio flash I have been able to use Speedlites and E-TTL in bright light more than ever before. I’ve also worked out why you need two, or more flashes in bright light.

E-TTL clever tech for automatic flash exposure

E-TTL is really clever, it’s designed to locate the part of the frame that is lit with flash and concentrate on getting the exposure for those parts correct. It does this by using a pre-flash that is 1/32 power. The problem in bright light is that the pre-flash might not be bright enough to see where the flash subject is and how much more or less light needs to be used to light the subject.

Two Speedlites – double the power

Automatic E-TTL flash exposure more consistent with two Speedlites in bright light

Two Speedlite 600EX-RT flashes in a Lastolite Ezybox II Medium Softbox

With off-camera flash, each flash is assigned to a group, up to five of them with radio, and just three with optical wireless. Adding another Speedlite in the group is largely invisible to the camera that’s doing the clever flash exposure metering. So if there’s two flashes in the same group, then you get two flashes firing a pre-flash at the same time doubling up the effective power on the subject from 1/32nd to 1/16th. The camera sees this much more clearly and is better able to gauge the correct exposure required for the picture.

I use a couple of Lastolite brackets to put two (Lastolite Ezybox II Speedlight Bracket) or four (Lastolite Ezybox Quad Bracket) Speedlites in the same place or modifier.

If you are not sure whether another flash will help, try taking a picture with a single flash in manual at 1/32nd power, if you can see a difference compared to no-flash on the camera LCD, then it’s likely the camera can too. If not, then double up the flashes.

More Speedlites = more consistent E-TTL flash exposures in bright light

Automatic E-TTL flash exposure more consistent with two Speedlites in bright light

The old disused canal provides an endless range of locations, bridges provide shaded options for pictures.

Automatic E-TTL flash exposure more consistent with two Speedlites in bright light

Moving out from the bridge, and in to the bright early morning sun I continued to use the flash to add light to the model who would otherwise be in shadow.

Automatic E-TTL flash exposure more consistent with two Speedlites in bright light

Of course other brands make multi-flash brackets that can be used with a wide range of softboxes, umbrellas and other light modifiers, the key is to group the Speedlites together to increase the power of the pre-flash.

Huge thanks to Emma for modelling for me, make sure to check out her modelling page.

Gear used for these photos

  • EOS 5D Mark III
  • EF 17-40mm f/4L USM and EF 135mm f/2L USM
  • Speedlite 600EX-RT x 2
  • Speedlite Transmitter ST-E3-RT
  • Lastolite Ezybox II Medium Softbox
  • Lastolite Ezybox II Speedlite Bracket