Here are some examples of depth-of-field (DOF) manipulations on a few aerial images. The first example is generated simply to make the subject stand out from its background, while subsequent examples are attempts to fool the viewer into believing they are looking at a miniature of the subject (such as an HO scale diorama).
In this image (the eagle on top of the Idaho State Capitol, shot at a very long focal length from a helicopter) the foreground and background don’t really enjoy much distinction. Believe it or not the apparent “compression” of long lenses is actually a viewing distance issue, but that’s moot now. We’ll blur the background to make the subject stand out better.
The type of blur applied isn’t a simple Gaussian-that’s simply not sophisticated enough and produces a rather coarse result. You’ll notice that the blur is more pronounced toward the top of the image than at the bottom, and that even the minute details of the scaffolding are preserved. I’ll write a separate post explaining the software I use to produce the graduated effect-which is even faithful to the specified aperture-when I get a chance.
The above image of St. Alphonsus RMC main campus in Boise is a simple application of graduated blur (again, not a Gaussian application) in that there is a graduated defocus into the distance-and if you look closely, toward the camera from the hospital. The effect is one of miniaturization since an illusion is produced by the artificially limited DOF…you think you’re looking at a model. This particular example is challenging in that the mountains are actually several miles distant.
In this example I have manipulated the defocus, minimizing it around the lit football stadium so that it is still recognizable. The downtown Boise area is given the illusion of miniaturization, and the fact that the image was shot at night lends a very interesting effect-you won’t find many night aerials like this.
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