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.A9 test data on DxO Mark 77D test data on DxO Mark
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.
New sensor offers incredible performance; Excellent image quality at low & high ISOs; Very good dynamic range; Phenomenal 20fps burst speed & deep buffer; Very good battery life for a mirrorless; 4K video; Dual card slots.
Slow buffer clearing; Only one card slot is UHS-II compatible; Touchscreen underutilized; No lossless RAW compression option; No 4K/60p option.