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.A7S test data on DxO Mark E-M1 test data on DxO Mark
Exceptional rugged, weather-proof, professional build; Lightning fast contrast-detect AF, and phase-detect AF that makes Four Thirds lenses far more responsive; Tons of useful physical controls with immense customizability; Arguably the best image quality of any Micro Four Thirds camera we've tested to date; Large, sharp, high-resolution electronic viewfinder; Advanced Wi-Fi capabilities, including remote control shooting in PASM exposure modes.
Bigger and heavier than many other compact system cameras; Most expensive Micro Four Thirds camera on the market to date; Menu system and customization options have a steep learning curve; No optical low-pass filter means greater risk of moire; No built-in flash.
Outstanding high ISO performance; excellent dynamic range; 4K video recording (via uncompressed HDMI); XAVC S option for HD video; Slightly improved battery life over A7/A7R; Built-in Wi-Fi & NFC connectivity.
4K video requires expensive external recorder; Sluggish startup time; Loud shutter; Silent Shooting mode hurts image quality; Lacks a built-in, pop-up flash; Limited selection of native Sony FE lenses.