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.1DX Mark II test data on DxO Mark D7000 test data on DxO Mark
Very good image quality; Better than average noise vs. detail handling at high ISOs; Very good dynamic range in JPEGs, excellent in RAW files; Lots of high-end features in a relatively compact body; 6 fps burst mode.
Viewfinder not as accurate as specified; Viewfinder doesn't show ISO unless adjusting; No live histogram in Live View mode; No phase-detect Live View AF mode.
Excellent image quality, especially from RAWs; Fantastic high ISO performance; Fast autofocus with great tracking performance; 14fps burst rate; Amazing buffer capacity; 4K 60p video; Robust build quality.
Very heavy, bulky and expensive; Dual memory card slots use different formats; 29:59 continuous video recording limit; Touchscreen feels underutilized.