Certified Professional Photographer (CPP) Practice Exam

A filter factor of 3x results in how many stops of increase?

1. One

2. One and 1/3

3. Two

4. One and 1/2

The correct answer is: One and 1/3

To understand how a filter factor of 3x translates to stops of increase, it's important to grasp what "filter factor" means. The filter factor describes the multiplication of exposure required when using a filter. A filter factor of 3x means that the amount of light reaching the sensor is reduced to one-third, necessitating an increase in exposure to obtain the same level of brightness in the image. In terms of stops, each stop represents a doubling or halving of the amount of light a sensor receives. A filter that reduces light by a factor of 3 requires more light for the same exposure—this can be broken down into stops. When you move from a 1x exposure (no filter) to a 2x exposure (one stop), you've doubled the light exposure. However, with a filter factor of 3x, the decrease in light doesn't quite reach the next doubling (which would be 4x). The increase in exposure from a filter factor of 3x corresponds to an increment of approximately 1 and 1/3 stops. This is determined because: - The first stop brings your exposure up to 2x (which halved the light to 1/2 of original). - The second stop brings