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.GM5 test data on DxO Mark J1 test data on DxO Mark
Very small body, with solid feel; Fast AF; No-nonsense interface. Excellent video capture, Good picture quality.
Body could be smaller for sensor size; High ISO isn't as good as other compact system cameras; Battery life below average; Weak flash; Confusing controls.
Great image quality for a tiny camera; Excellent high ISO for its class; Built-in EVF; Built-in hot-shoe; Improved ergonomics; Improved image quality for long exposures; Improved burst rate with hybrid shutter; 1080/60p video.
Slightly bigger than GM1 (but not by much); No built-in flash; Shallow buffers with RAW files; Dynamic range not quite as good as some competing models; Below average battery life.