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So, here's the situation: We have a picture taken in the Hollywood Hills with a midrange digital camera, using the built-in automatic light meter. As a result, we have a nicely exposed sky, end everything else is lost in the dark.
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| The simplest answer, of course, is to adjust the image with Levels and/or Curves. Sometimes this will do the trick. Often, however, we will end up with a washed-out image like this. Additionally, the colors have gone awry. |  |
| Here is one solution. This is a variation of a technique demonstrated by Alex Lindsay at the MGLA a couple years ago, that was to even-out values for tiling textures, by use of the overlay mode in Photoshop (or After Effects.)
First, we need to review just what the Overlay Mode actually does. If you were to create a new layer above you image, and fill it with a neutral 50% gray, and apply the overlay Mode, you would see no change in you image. Pixels that are darker than this midrange gray, however, will darken the image, and pixels that are lighter than the midrange gray will lighten the image. In a color image, this will take place in each of the color channels. So what we want to do is reduce the contrast in our image, or, lighten the dark areas while darkening the light areas. |
| To do this we will want an image that is a negative of the image we are working on. That is, an image that is dark where our image is light, and light where our image is dark. |
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| First, we duplicate our image on a new layer above the original image.
Next, use "Invert" under Photoshop's "Image" menu, under "Adjustments." This gives us a negative image. In this case, we do not want color information, so we will use the Hue/Saturation controls to completely desaturate the image. It is also a good idea to blur this image substantially using the gaussian blur filter. I find a setting between 3-5 to work well. And Now, change the Apply Mode to "Overlay" on the Layers palette. Sometimes the effect is too extreme, and needs to be reduced, which is simple enough using the opacity slider in the layers palette. |
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Depending on the image, you may now wish to adjust curves or levels to attain the desired results. In this instance we were able to retrieve a good deal of the detail that had been lost in darkness.
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A variation on this technique, and closer to Alex Linday's original demonstration, is to work in the Lab color space, rather than in RGB. In the Lab color space, there is one channel for value, or Lightness (L), and two for color (a & b). By using Only the L channel, and creating a new layer above that, the above technique does not require desaturation, and will perform all operations without touching the color of the image. More on the use of the Lab color space in Part Three.
To see more of Alex Lindsay's work and extremely useful tutorials, visit www.dvgarage.com. |
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