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.A7 III test data on DxO Mark A7R IV test data on DxO Mark
New 24MP sensor offers excellent image quality; Outstanding high ISO performance and dynamic range; Improved JPEG colors; Improved build quality; Fast autofocus; Excellent 4K video; Very good battery life.
Buffer clearing can be slow even with fast UHS-II cards; UHS-II support only on one card slot; No losslessly compressed RAW option; Dedicated battery charger not included; Menus are still confusing; No built-in flash.
Outstanding image quality; Excellent high ISOs; Fast AF performance with Eye-AF tracking; 10fps bursts at full-resolution; Improved ergonomics; Dual UHS-II card slots; Higher-res EVF.
Expensive; No 4Kp60; Buffer clearing could be faster; Menus are still frustrating; Touchscreen underutilized; No built-in flash.