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.RX1R II test data on DxO Mark RX1 test data on DxO Mark
Full-frame, 24-megapixel sensor in a compact body; Carl Zeiss Sonnar 35mm f/2 T* lens; Blazing fast autofocus; Impressive image quality that rivals (and sometimes surpasses) full-frame DSLRs; Customizable function buttons make it a breeze to use.
Fixed-length lens limits shooting flexibility; Some exposure bias, color shift, moire and video AF issues; Viewfinders (optical or electronic) only available as optional accessories; Extremely expensive for a compact camera.
Excellent image quality; Extremely high resolution; Surprisingly good high ISO performance; Outstanding dynamic range; Handy variable low-pass filter; Fast phase-detect AF; Built-in EVF.
Fixed, single focal length lens; Poor battery life; No built-in flash; No touchscreen LCD; Slow buffer clearing; No 4K video; Expensive.