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-1 test data on DxO Mark D610 test data on DxO Mark
Eliminated sensor dust-and-oil spot issue from D600; Great controls for amateur or pro; Comfortable ergonomics and weight; Excellent image quality and low-light performance; Very good dynamic range; Excellent battery life; Built-in lens correction.
Not drastically different from D600; Moire with certain subjects; Auto WB still too warm in incandescent light; Slow AF in live view mode; Aliasing in videos.
Unlocks the full potential of full-frame Pentax lenses; Excellent image quality; Great ergonomics and build; Very compact for full-frame; Decent performance; Fast autofocus with great low-light capabilities; Very wide sensitivity range; Bright, accurate viewfinder; Articulated LCD; Stabilization, Wi-Fi and GPS in-camera
No built-in flash strobe; Quite heavy compared to APS-C flagships; Somewhat soft images and blown highlights by default in JPEG mode; Warm Auto white balance indoors; Slow startup and buffer clearing; Small top-deck status display; Weak viewfinder illumination; Below-average battery life for DSLR