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.6D Mark II test data on DxO Mark 6D test data on DxO Mark
Excellent image quality on par to more expensive full-frame DSLRs (including the 5D Mark III); Responsive all-around performer; Superior HD video-shooting chops; Built-in Wi-Fi with remote control and sharing features, Built-in GPS and geotagging.
Lacks a built-in, pop-up flash; No external headphone jack; Rather basic 11-point autofocus system; Mediocre burst speed.
Great vari-angle touchscreen; Dual Pixel CMOS AF; Good image quality in most situations; Impressive performance for its class.
Disappointing dynamic range; No 4K video; Optical viewfinder comes up short; Narrow AF point coverage through viewfinder.