Certified Professional Photographer (CPP) Practice Exam

What is the formula called that relates bellows extension to focal length?

1. Bellows Factor

2. Bells Factor

3. Exposure Factor

4. Bellows

The correct answer is: Bellows

The formula that relates bellows extension to focal length is commonly referred to as the Bellows Factor. This concept is crucial in the realm of photography, especially when using large format cameras, because extending the bellows of the camera affects the effective aperture and, consequently, the exposure. The Bellows Factor provides a way to calculate the changes needed in exposure settings when the bellows are extended from their standard position. As the bellows are extended, the effective aperture decreases, meaning more light is needed to achieve the same exposure. This factor quantifies that relationship, allowing photographers to make appropriate adjustments to shutter speed or ISO to compensate for the exposure change caused by the bellows extension. Understanding this formula enables photographers to maintain proper exposure in their images, especially in macro or close-up photography, where bellows usage is more common. The other names listed do not accurately represent this specific concept, reinforcing that "Bellows Factor" is indeed the correct terminology used in photography regarding this relationship.