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.A7 test data on DxO Mark SL (Typ 601) test data on DxO Mark
Incredibly small body for a fully-featured, full-frame camera; Very high resolution; Hybrid autofocus is reasonably fast and confident; Significantly better burst-shooting performance than A7R; Excellent image quality even at very high sensitivities; Faster x-sync than A7R; Accepts existing Alpha-mount and E-mount lenses, and can optionally crop to APS-C image circle.
Grass-is-greener syndrome when compared to its higher-res sibling; Moderate performance; Loud shutter (but electronic first-curtain helps); Mediocre battery life when using electronic viewfinder; Weak low-light autofocus considering its price; Limited selection of native Sony FE lenses.
Superb build quality; Amazing EVF; Great image quality from RAW files; Good high ISO performance; Very good dynamic range; Very low shutter lag; Fast AF on stationary objects; Class-leading ~11 fps burst mode; 4K DCI and UHD video; Full HD up to 120p. Built-in Wi-Fi and GPS; Dual card slots; Decent battery life for its class.
Big for a full-frame mirrorless camera; Very slow buffer clearing; Contrast-detect AF system struggles with moving subjects; In-camera JPEGs are muted and dull; Very limited native lens selection (but supports many other Leica lenses via adapters); Expensive.