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.NEX-6 test data on DxO Mark NEX-5R test data on DxO Mark
Very good image quality; More consumer-friendly control setup than NEX-7 but more advanced (actual Mode dial) than step-down models; OLED EVF and 3-inch tilting LCD monitor provide viewfinder flexibility; Fast and decisive AF on stationary subjects, and good continuous AF on normal moving subjects; Full HD 1080p video recording at up to 60p.
Hybrid AF system speed and accuracy still lags somewhat behind higher-end DSLRs; Wi-Fi features still rudimentary (join the club); LCD is not a touchscreen; User interface foibles.