Certified Professional Photographer (CPP) Practice Exam

If E = F8 @ 125 and E = F11 @ 60, what is E = F16 @ ?

1. 30

2. 45

3. 60

4. 75

The correct answer is: 30

To solve for the exposure equivalent at F16 when given the exposure equivalents at F8 and F11, it is essential to understand the concept of f-stops and their relationship to exposure. Each full stop change in aperture (either opening it up to a larger number or stopping it down to a smaller number) halves or doubles the amount of light hitting the sensor, respectively. In this case, moving from F8 to F11 represents a one-stop decrease in light, while moving from F11 to F16 represents another one-stop decrease. Given that E = F8 @ 125, if we stop down to F11, we need to double the exposure time to maintain the same exposure level, which changes it from 1/125 seconds to 1/60 seconds. Now, moving from F11 to F16 means we are decreasing the light again by another stop, which would require doubling the exposure time again. Starting from E = F11 @ 60, we double the exposure time to maintain equivalent exposure at F16. Doubling 60 seconds gives us 120 seconds total. However, since we're typically expressing times in fractions of a second in photography, this translates to a balanced exposure equivalent of 1/30 seconds (as