Bit level for a CCD (Charged coupled device) with a greatest possible pixel value of 4095:
The relationship between the bit level and pixel value is given as:
pixel value = 2^bit level.
Most charged coupled devices (CCDs) have 8-bit, 16-bit, 32-bit levels.
Using simple mathematics, we can see that 2^12 = 4096.
Since the maximum number of pixels is 4095, the bit level is 12., i.e. the CCD has 12-bit level.
Another way to solve this problem is by representing bit level by 'b',
then 4095 = 2^b.
Taking logarithm of both sides, log (4095) = b log (2) [using the standard logarithmic identity of log x^y = y log x).
or b= log (4095)/ log (2) = 3.61225/0.30103 = 11.9996 or 12-bit as already calculated.
hope this helps.