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.K-5 IIs test data on DxO Mark K-500 test data on DxO Mark
Noticeably better sharpness than standard K-5 II; Compact yet control-rich body packs in the features; Updated autofocus system focuses in near-darkness; Fully weather-sealed; Very good dynamic range; In-body image stabilization; Dual-axis level with horizon correction.
Prone to moire, aliasing, and false color artifacts; Can seem intimidating at first; Fewer autofocus points than competitors; Doesn't take advantage of high-speed UHS-I flash cards; Movie feature set is very dated and file sizes huge.