Certified Professional Photographer (CPP) Practice Exam

How does an ISO 200 film compare to an ISO 100 film in terms of light sensitivity?

1. It is four times less sensitive

2. It is half as sensitive

3. It is twice as sensitive

4. It has no difference in sensitivity

The correct answer is: It is twice as sensitive

ISO ratings indicate the sensitivity of film (or digital sensors) to light. An ISO 100 rating means that the film is designed to be sensitive enough to effectively capture an image in a certain light level. When moving to an ISO 200 rating, the film becomes more sensitive to light. This increased sensitivity means that ISO 200 film can capture an image in half the amount of light that would be needed for ISO 100 film. In practical terms, this allows photographers to use faster shutter speeds or smaller apertures in the same lighting conditions, which can be advantageous in various shooting scenarios. The relationship between ISO numbers is logarithmic; specifically, each time the ISO value doubles (from 100 to 200, for instance), the sensitivity doubles as well. Therefore, ISO 200 film is indeed twice as sensitive as ISO 100 film, enabling more versatility in low-light conditions and the potential for better image quality without the need for additional lighting. This clarity in understanding sensitivity is crucial for photographers when deciding which film or settings to use based on their environmental lighting conditions.