Small imperfections that can be retouched. The sensor may have dust that shows up on the image as dark spots. A portrait subject might have a small blemish that will be very noticeable when you enlarge the image. Small areas may benefit by being made a little lighter or darker than their surroundings.

Evaluating Sharpness
The apparent sharpness of an image depends a great deal on how much contrast there is along edges and lines. If an image looks soft, it can often be improved by sharpening, that adds contrast along lines and edges.
Evaluating Noise
If you used a long shutter speed or high ISO setting to take a photo, it may contain noise. Look in dark areas for randomly colored pixels that look like grain.

Global vs Local Editing
You may have noticed that some of the adjustments discussed in this section affect the entire image and others affect just specific areas. These are referred to as global and local adjustments.