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.A99 II test data on DxO Mark D5200 test data on DxO Mark
Captures sharp, detailed photos with its new 24.1-megapixel CMOS sensor, even at higher ISOs; Features a familiar (D5100) but refined body design; Records Full HD video with full-time autofocus tracking; Packs a ton of advanced features into a consumer-friendly body at a great price.
Autofocuses a little slowly for its class and struggles at times in low light; Changing some basic settings takes more time and effort than it should; Mediocre kit lens.
Superb image quality at low, moderate ISOs; Improved high ISO performance; Fast continuous shooting speeds; Very impressive hybrid autofocus; High-quality 4K UHD video; Rugged camera body.
Multi-selector joystick can be awkward to use; No EVF live view at fastest burst rate; Buffer clearing is slow with no UHS-II support; 4K UHD video isn't as full-featured as E-mount counterparts.