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.5DS R test data on DxO Mark 7D Mark II test data on DxO Mark
Excellent image quality; High ISO performance improved over predecessor; Excellent burst speeds (up to 10fps); Significantly improved buffer depths; 65-pt AF system; Dual Pixel CMOS AF; Can focus down to f/8 (great for teleconverters); 1080/60p video; Headphone and mic jacks; Rugged build quality.
Autofocus speed (AF shutter lag) slower than 7D and 70D; Mediocre battery life for a pro DSLR; Dynamic range at low to moderate ISOs not as good as competitors; Phase-detect AF did not perform as well as expected in our low-light AF tests; No built-in Wi-Fi; No autofocus for 1080/60p video.
Phenomenal resolution and sharpness; Fine Detail Picture Style is like in-camera Unsharp Mask; Excellent print quality; Decent high ISO performance; Improved normalized dynamic range compared to 5D Mark III; Decent burst speed with good buffer depths; Built-in intervalometer & timelapse movie mode.
AF speed tested closer to consumer-level DSLRs; Dynamic range lower than competing models from Nikon & Sony; Lack of OLPF means subject to more aliasing artifacts with some subjects; No 60p video frame rate; No headphone jack; Timelapse video is only 1080p.