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.D750 test data on DxO Mark D500 test data on DxO Mark
Outstanding image quality with great dynamic range and high ISO performance; Class-leading burst rate; Very good 51-pt AF system; AF system works in very low light; Deep, comfortable handgrip; Articulated LCD monitor; Excellent battery life; Uncompressed 4:2:2 HDMI video output; Built-in Wi-Fi.
Buffer fills quickly with 14-bit RAW; Sluggish Live View AF; Shutter speed tops out at 1/4000s; OVF coverage closer to 97%; Weak low-pass filter is great for detail but higher risk of moire.
Superb image quality; Great high ISO performance; Rugged, comfortable camera body; Sharp articulating touchscreen display; Excellent AF point frame coverage; Fast continuous shooting speeds; 4K UHD video; Built-in Wi-Fi, NFC and Bluetooth.
Somewhat large for an APS-C camera; Expensive for a DX camera; 4K UHD video doesn't offer full DX field-of-view; No built-in flash; Still uses contrast-detect for Live View AF; Dual slots use two different card types (XQD and SD).