In low light, how does increasing ISO affect image noise, and what strategy minimizes noise?

• A. Higher ISO reduces noise; use higher ISO
• B. Higher ISO increases sensor sensitivity but also noise; use lower ISO with longer exposure or more light
• C. Higher ISO reduces exposure time
• D. Noise is independent of ISO

Answer: (B)

In low light, raising ISO makes the sensor more sensitive to light, which helps brighten the image but also amplifies the electronic and random variations that show up as noise. Because the same amplification that brightens the image also boosts these unwanted signals, noise increases with higher ISO.

To minimize noise, keep ISO as low as possible and compensate with more light or a longer exposure. Using a longer exposure (often with a tripod to avoid camera shake) or adding light to the scene lets you achieve a proper exposure without cranking up ISO. If you can’t increase light, opening the lens (wider aperture) can help, but be mindful of depth of field and potential blur. Shooting in RAW and reducing noise in post can also help, but the primary strategy is lower ISO with more light or longer exposure.