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.A7R III test data on DxO Mark D5300 test data on DxO Mark
Excellent image quality similar to more expensive DSLRs (like the D7100); Great dynamic range; Responsive all-around performer; Excellent Full HD video-shooting quality; Built-in Wi-Fi with remote control and sharing features; Built-in GPS; Compact and lightweight size; 18-140mm kit lens performs well for its type and has a very versatile focus length range.
AA-filterless sensor makes it more prone to moire; Burst speed slows with highest quality 14-bit RAW images; Live View mode not as good as some competitors; No external headphone jack; GPS receiver not very sensitive.
Fantastic image quality; Improved dynamic range over its predecessor; Very good high ISO performance; Much improved real-world AF performance; Class-leading burst rates, even with RAW; Improved 5-axis in-body image stabilization; Better 4K video quality; 1080/120fps video; Dual card slots; Significantly better battery life.
Expensive; Menus still confusing; UHS-II support only on one card slot; No optical low-pass filter means greater risk of moire; No built-in flash; Buffer clearing still slow despite UHS-II support.