Film speed is a measure of a film's sensitivity to light.
In photography, film speed is a critical characteristic that determines how much light is needed to create a proper exposure on the film. A film with a higher speed is more sensitive to light than one with a lower speed.
Understanding ISO Rating
Film speed is commonly referred to as the film's ISO rating. ISO stands for the International Organization for Standardization, which standardized film speed measurements. This rating provides a numerical value that indicates the film's sensitivity.
- A lower ISO number signifies lower sensitivity (often called "slow" film).
- A higher ISO number signifies higher sensitivity (often called "fast" film).
Common Film Speeds
As noted in the reference, some of the most common film speeds you might encounter include:
- ISO 100
- ISO 200
- ISO 400
Using a higher ISO film allows photographers to shoot in lower light conditions or use faster shutter speeds to freeze motion, because less light is required to achieve a correct exposure. Conversely, using a lower ISO film is typically preferred in bright light and often results in finer grain and higher image resolution.
Knowing the film speed helps photographers select the right film for the shooting environment and adjust camera settings (like aperture and shutter speed) to achieve the desired exposure and look for their photographs.
