As was seen in previous section light adaptation in photodetectors is rather limited. This is due to the nature of photodetectors, i.e. hard-wired structures. There is more flexibility on the design of photocircuits, as evidenced in section 7.3. Almost all structures described in that section provide some method of adaptation. Those photocircuits with logarithmic compression already have a builtin adaptive mechanism. The logarithmic compression provides a large dynamic range of operation. The boundaries of the compression are determined by uncontrollable transistor characteristics. In the lower end it is limited by the leakage current and noise, and at the higher end by the saturation of transistors. Adaptation in these photocircuits is local. The reader is referred to the material in section 7.3 for more information on adaptive photocircuits.
In integration based photocircuits, used in many imagers, adaptation can be achieved by controlling the integration time. For low light levels long integration time can be used and for higher light levels, shorter integration time. In the lower end of light intensity the integration time is limited by the dark current, and at the higher end by the maximum clock frequency.