Math
posted by Jus on .
The aperture setting, or fstop, of a digital camera controls the amount of light exposure on the sensor. Each higher number of the fstop doubles the amount of light exposure. The formula n=log_2(1/p) represents the change in the number, n, of the fstop needed, where p is the amount of light exposed on the sensor.
a) a photographer wishes to change the fstop to accomodate a cloudy day in which only 1/4 of the sunlight is available. How many fstops does the setting need to be moved?
My answer:
2 (which is correct)
b) if the photographer decreases the fstop by four settings, what fraction of the light is allowed to fall on the sensor?
I need help on part b. My attempt is this:
4p=log_2(1/p)
then I solved for p, and got 1/2 but it is wrong.

4=log(base 2) 1/p
2^4 = 1/p
16 = 1/p
16p = 1
p = 1/16