Maximum effective ISO is an estimate of the highest sensitivity at which a camera can capture excellent quality photos.
Cameras with higher effective ISO will be better choices for indoor photography, night shooting, and indoor sports photography, especially if you intend to make large prints.
You can learn more at our glossary entry.
Maximum effective ISO test data courtesy of DxO Mark.D3300 test data on DxO Mark 77D test data on DxO Mark
Excellent image quality with lots of fine detail; Very good high ISO performance; Good dynamic range; Good print quality; Deep buffers with JPEGs; 1080/60p video; Uncompressed HDMI output.
AF struggles in low-light; Contrast-detect AF in live view is slow; Buffer depth is shallow with RAW files; No AE bracketing; No built-in Wi-Fi.
Very good image quality; Improved dynamic range at low ISOs; Very fast autofocus; Dual Pixel CMOS AF in Live View; Much improved RAW buffer depth; 1080/60p video; Quick Control Dial & top-panel LCD screen.
Default JPEGs slightly soft straight out of camera; Dynamic range & high ISOs lag behind competing cameras; No 4K video resolution.