To measure between 10 and 100, however, you must boost the gain by a factor of 10, because the resolution of the answer is only two digits. Similarly, to measure between 1 and 10 you must boost the gain by a factor of 100 to get three digit resolution again. Transimpedance amplifiers simulate integration by taking multiple samples and calculating the average reading. This technique is sufficient if the sampling rate is at least double the frequency of the measured signal. The ability to sum all of the incident light over a period of time is a very desirable feature.
Photographic film is a good example of a simple integration.
The image on the emulsion becomes more intense the longer the exposure time. An integrating radiometer sums the irradiance it measures continuously, providing an accurate measure of the total exposure despite possible changes in the actual irradiance level. The primary difficulty most radiometers have with integration is range changes. Any gain changes in the amplification circuitry mean a potential loss of data. For applications with relatively constant irradiance, this is not a concern.