Digital Photography Tip: "Exposure Stacking"

Have you ever had a problem trying to shoot a scene with a bright sky and dark foreground and finding that if you get the sky exposed right then the foreground is black, and if you get the foreground right then the sky is over exposed? This is especially common with sunrise and sunset photos. With film cameras the only real option is to try to balance the light in camera with split filters or holding a black card in front of part of the scene during long exposures to “hold back” some of the bright areas. Digital photography provides some new ways to achieve a balanced shot when the light range is too great. One way involves making two exposures of a scene and bringing them together in Photoshop that I call “exposure stacking”.

I employ some sort of “exposure stacking” technique in many of my landscape photos especially when the dynamic range of a scene or complexity of the skyline make use of graduated filters problematic. If you would like to try, follow these steps.

1. Set up your camera on a sturdy tripod. Once you have framed your shot, lock everything down so there will be no unwanted movement.
2. With the camera set to aperture priority or manual, take one shot at one to two stops above your meter reading. Now, without moving the camera, adjust the shutter speed to take another shot at one to two stops under your meter reading.
3. Open both images in Photoshop and select the move tool on the tools pallet. Holding the shift key, drag the darker image on top of the lighter image. Holding the shift key will make the two images line up on top of each other.
4. In the layers Pallet you will now see two layers, the light one on the bottom and the darker one on top. Make sure the top dark layer is selected and then click the “Add A Mask” button at the bottom of the layers pallet (it looks like a folder with a circle in it).
5. Now select the brush tool on the tools pallet. Make sure that the foreground color on the tools pallet is set to black. With the brush opacity set to about 30% begin painting on the image mask. Everywhere you paint on the mask the top layer will be erased 30% at a time allowing the lighter bottom layer to show through. If you erase too much you can bring it back by setting the foreground color to white and painting over the erased areas to “un-erase” them.
6. In this way you can bring out the lighter foreground exposure while leaving the sky appropriately exposed. It takes a little practice to get the best results and sharp edges along a light/dark boarder can be tricky, but this technique can make otherwise impossible photos possible. Give it a try!