Feature: Perfect Pictures With a Double Exposure

Photographers use double exposures for all sorts of clever tricks. With a film camera on a tripod, I once used a multiple exposure to photograph myself manning every position around a high-tech piece of gear in a physics lab. A few weeks ago, we used the digital equivalent of a double exposure to create an artistic soft focus around a flower. The same technique has a genuinely useful application, though: fixing the exposure in a picture.

Exposure Control and Multiple Exposures

So how does this work? It's pretty simple in theory. Last week, I suggested that you could use the exposure lock button to frame a shot while bringing out the details in the darker parts of your picture. I also suggested you could get the opposite result by locking the exposure on the sky to keep it rich and colorful.

Here's the trick: If you take both pictures, you can combine these "opposite" shots using the layers tool in your image editing program to keep just the bits you like from both. It's that easy!

Taking the Pictures

I know you're familiar with using your digital camera's exposure lock feature. (You did go back and reread my last column, didn't you?) So, suppose you see a scene like a sunny day at the playground.

When you lock the exposure on the sky and snap the picture, you'll preserve the detail in the highlights. To get the darker bits exposed properly, point the camera at the shadows, lock the exposure, and take a second shot.

One word of advice: For best results, the pictures should be composed identically. That means using a tripod. Lock the camera in position so you can only swing it up and down to lock the two different exposures.

Loading Into Layers

Now it's time to load the two images into your image editor (save them to your hard drive first, of course). We'll use Jasc Paint Shop Pro for this example, but almost any editor with layers will work just fine.

With both images open, click the one with the badly overexposed sky and foreground. You'll notice that the picture is a disaster for the most part,except for the shadows. Choose Edit, Copy from the menu and then click on the other image. Choose Edit, Paste, Paste As New Layer. That image should disappear, replaced by the overexposed scene. Don't worry--they're both still there, only the clear blue sky and sharper overall level of detail are hidden in the lower layer.

Erase the Top Layer

Now it's time to use your artistic skills to erase the top layer, revealing the one underneath. Choose the Eraser tool, which lives in the eleventh cubby from the top of the Tools Palette on the left side of the screen. Be sure not to select the Background Eraser, which also lives in that cubby.

Click on the picture and start "painting." As you do so, you'll see that you're erasing the top layer so the bottom layer can show through. You may need to erase carefully and possibly even change the size of the Eraser via the Tool Options Palette at the top of the screen. For my picture, I erased all of the top layer except for the perfectly exposed shadow area in the bottom right of the screen.