Figure 6.34: a) profile in a sharp image; b) profile in an unsharp image.
When focusing your camera, it might help to take a quick look at the gray-value transitions along a line within the image to see whether the edges are sharp or still a bit blurry. While sharp images are defined by abrupt changes between dark and bright gray values, no abrupt changes but rather gray-value transitions can be found in blurry images (see figure 6.34).