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.645Z test data on DxO Mark A7 III test data on DxO Mark
Phenomenal resolution and detail; Great high ISO performance; Rugged, weather-sealed body; Huge, bright viewfinder; Fast autofocus works well in low light; Swift performance for a medium-format camera; Good battery life; Shoots Full HD video
Quite bulky compared to an APS-C or full-frame DSLR; Autofocus points clustered near center of frame; Most lenses aren't weather-sealed or optimized for digital; Prone to aliasing artifacts (but so are most high-end cameras these days); Attracts a lot of attention from passers-by
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.