Certified Ophthalmic Medical Technologist (COMT) Practice Exam

When comparing films rated at 400 ISO and 100 ISO, which film is more sensitive to light?

1. 100 ISO

2. 400 ISO

3. Both are equal

4. Neither is sensitive

The correct answer is: 400 ISO

The film rated at 400 ISO is more sensitive to light compared to the film rated at 100 ISO. ISO, or International Standards Organization, measures a film's sensitivity to light; the higher the ISO number, the more sensitive the film is. A film with a higher ISO can capture images in lower light conditions without requiring an extended exposure time. Thus, a 400 ISO film requires less light to expose an image adequately than a 100 ISO film. This characteristic makes 400 ISO film particularly useful in situations with limited lighting, or for capturing fast-moving subjects with shorter exposure times. Consequently, in practical applications, photographers often select higher ISO films for specific scenarios to achieve better results without increasing exposure times or compensating with additional light sources.