Complete dark adaptation takes about 30 minutes, as you can see from the figure below, which shows the standard dark adaptation curve. You may find the form of the curve slightly confusing, because increasing sensitivity to light over time is shown by a falling curve. The reason the curve falls is that what is being measured is the amount of light necessary for an observer to detect something. As sensitivity increases, the amount of light necessary for detection decreases, and the curve falls. Also, you will note that the curve has two distinct segments; there’s an initial increase in sensitivity that takes about 7 minutes, followed by another and much greater increase that’s through in about half an hour. The first part of the curve, which enabled Seth to see some empty seats near him, is the cone segment. As you can guess, the second segment is the rod part of dark adaptation. The increasing sensitivity in both types of receptors is caused by the regeneration of photochemicals in the rods and cones that are degraded by exposure to light. In addition to the regeneration of photochemicals, your pupils also dilate to let in more light. Because this happens almost immediately, you can see that most of dark adaptation comes through changes in the cones and rods.

Figure 5, curves of dark adaptation, from Goldstein, S & P, p. 78