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Dynamic Range
The dynamic range is often represented as a log ratio of well depth to the readout noise in decibels. For example, a system with a well depth of 85,000 electrons and a readout noise of 12 electrons would have a dynamic range = 20 log (85,000/12), or 77dB. The higher the number the better.
This ratio also gives an indication of the number of digitization levels that might be appropriate for a given sensor. A sensor with a well depth of 35,000 electrons and with 15 electrons of read noise would yield a ratio of 35,000/15=2333. Unless there is a desire to resolve this noise with a 16 bit system into 65,536 gray shades, a 12 bit system with 4096 levels would be more than adequate for this sensor. In this case, about 2 counts of noise would be digitized with the signal. For a KAF-1300, which has a well depth of 150,000 electrons and 15 electrons read noise, the ratio becomes 10,000, or 80dB. This sensor would be most suited for 14 bit digitization (16384 levels). For the SITe-based AP7, with a well depth of 350,000 electrons and 15 electrons of noise, the ratio becomes 23,333, or 87dB. Digitization to 16 bits is appropriate in this case. The typical values achieved for the AP7b with the SITe CCD is a noise of 9e- and a digitized well depth of 300Ke-. This yields a dynamic range of 33.3K:1 or 90.4dB, OR just over 15 bits.
