Certified Professional Photographer (CPP) Practice Exam

If a filter factor requires opening the lens by 2x, how many stops should you open it?

1. Two

2. One

3. Three

4. Half

The correct answer is: One

To determine how many stops to open the lens when a filter factor requires a doubling of light, it’s important to understand the relationship between stops and exposure. Each full stop of exposure either doubles or halves the amount of light hitting the sensor. When a filter factor necessitates that you open the lens by 2x, you are effectively allowing twice as much light to reach the camera sensor compared to a situation where the lens is not opened. This is equivalent to increasing the exposure by one full stop. In practical terms, if you were to open the aperture one stop, you would be doubling the area of the lens opening, which in turn doubles the amount of light entering the camera. Thus, if the filter factor indicates that you need double the light, you adjust your lens by one stop to achieve this increased light intake. Because of this principle, opening the lens by 2x directly translates to just one stop adjustment.