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.5D Mark III test data on DxO Mark 70D test data on DxO Mark
Superb still and video image quality; Powerful, fast, and accurate AF system with loads of cross-type points, loads of configurability and great frame coverage; Rugged, weather-sealed body with great control layout and user-interface configurability.
Dynamic range is limited by noise in deep shadows; Somewhat heavy-handed noise suppression and sharpening at default settings. (Shooting RAW avoids both.); No AF illuminator.
Dual Pixel CMOS AF delivers full-time continuous autofocus (with phase detect at every pixel in framing area) for video and Live View still shooting; Full HD (1080p) video recording with pro-level features and quality; Improved resolution and good high ISO performance; Excellent Wi-Fi remote shooting with full exposure controls; 3-inch articulating LCD touchscreen.
Image quality only improved slightly over 60D; Dynamic range still lags behind competing models; May not feature enough upgrades to convince people to step up from 60D.