Off-camera flash on location – part 4
We hope that you’re enjoying our series on off-camera flash on location, where we aim to demystify this popular and enjoyable sub-genre of portrait photography. So far in this series we’ve covered the equipment you’ll need, scouted some great locations and shown you how to get started on making some cool exposures.
This week we’re going to give you the lowdown on balancing your flash and ambient exposure by making adjustments in-camera – it really is like magic!
We’re going to keep it as simple as possible for now, and whilst there are exceptions to this rule, it’ll get you working as long as ISO is a constant:
1. Shutter speed controls the ambient exposure
2. Aperture controls the flash exposure and ambient
Changing the ambient exposure in-camera
Having your ambient a little underexposed is a great place to start for dramatic portraits because it allows you to properly expose your subject with the flash, and make them ‘pop’ out of the background. It’s also a great way to keep sky detail in the shot should you wish to.
To control the ambient, simply increase or decrease your shutter speed in-camera – increase to lighten, decrease to darken. As long as you stay within the sync speed of your camera, this will be effective.
Changing the flash exposure in camera
Now, when it comes to the flash exposure things get a little more interesting…
Let’s assume that you have your ambient dialled in at 1/125th of a second to underexpose the scene by a whole stop. You’ve brought your umbrella stand with your flash in on ¼ power, with your aperture set at f/5.6 – but your subject is about a stop overexposed.
You could walk to the flash and reduce the power, but sometimes that ruins the flow of a shoot and it’s necessary to make adjustments in-camera. If we close our aperture down by a stop we’ll have a perfectly exposed subject, which is great, but look what happens to the ambient – it’s now two stops underexposed.
How do we fix this? We simply open up our shutter speed to 1/60th to compensate! Can you see why this is a dance now? If you open your aperture one stop you need to balance that by decreasing your shutter speed to compensate: one goes up as the other goes down, and vice versa.
We encourage you to get out and practice this because it’s much easier to get your head around in practice than theory, so find a willing victim and start shooting!