Using Exposure Compensation for flash photography
Today’s post is somewhat of a follow up from my post a few week back reviewing the PocketWizard TT1 and FlexTT5 units. I want to talk about a really cool way to adjust the look of your flash images that is so easy to do using Exposure Compensation. Most of you I am sure know what exposure compensation is for your normal non flash photography. If you are using Aperture Priority or Shutter Priority to shoot with you can use the Exposure Compensation dial on your camera to under or over expose the image by dialing it in different exposure levels. I use it all the time, for weddings I might be shooting the groomsmen outdoors and with mostly black in the frame from their tuxes it will trick your cameras meter. I’ll use exposure compensation to quickly underexpose the image by 1-2 stops which will give me the correct exposure.
When you are using flash exposure compensation works a little bit different. But before we get into it a quick refresher for us all on flash photography and exposure. When dealing with flash photography a good thing to remember is that your shutter speed is really controlling the ambient light that is let in and your aperture is exposing for the flash. What I mean by this is that since your flash is firing at such a fast speed (faster than the shutter) the shutter speed that you are shooting at is does not effect the exposure of your subject. The aperture (and power of flash) you set will control the exposure of your subject while the shutter controls the background exposure. When shooting outdoor portraits with ETTL flash getting a very dramatic blue sky or background is actually very simple.
All you have to do is set your camera to Aperture priority and set the aperture at your desired setting. For me I love soft backgrounds and usually am shooting at 2.8 or maybe f/4. I set my flash to ETTL on a PocketWizard FlexTT5 unit, which is normally off camera with an umbrella. First leave your exposure compensation set to 0 and fire a shot. This will give you an average image with the background “properly” exposed.
Then where the magic happens is using exposure compensation. Remember since your flash isn’t adjusted by the shutter speed only the background is, all you have to do is use the Exposure Compensation dial on your camera and underexpose the image by a stop or two. In this example I set the Exposure Compensation to -2 and you can see how much deeper the background gets. The couple is still exposed properly just the background gets darker by underexposing the background.
Give it a try next time you are out shooting and let me know how it goes. We have a entire series of lighting articles coming up so keep checking back.
Also here are a few links for other lighting articles you might have missed in the past:
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