In a low light setting, which ISO would be best?

• A. 100
• B. 1600
• C. 400
• D. 800

Answer: (B)

When light is scarce, you boost sensor sensitivity. ISO controls how sensitive the camera sensor is to light, so raising ISO lets you capture enough exposure with a faster shutter speed or a smaller aperture. This is crucial in low-light settings to avoid blurry images from camera shake or subject movement.

Using a higher ISO, like 1600, gives you the needed brightness without sacrificing too much sharpness, especially if you can’t open the lens wide or lengthen the exposure excessively. The lower sensitivities—100, 400, or 800—would require more light from the scene, slower shutter speeds, or a wider aperture to reach proper exposure, which increases the risk of motion blur or limited depth of field in dim environments. The trade-off with higher ISO is more digital noise and reduced image quality, but in many low-light situations the ability to obtain a usable image quickly outweighs that cost.