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.E-PM2 test data on DxO Mark A55 test data on DxO Mark
Super compact and lightweight; Excellent image and print quality that rivals much more expensive CSCs and DSLRs; Solid low-light (high ISO) performance; Touchscreen LCD responsive and useful once you get used to it; Speedy and accurate AF on still subjects; Tons of advanced shooting features and customizing options.
Maddening menu system; No physical Mode dial; Motion AF not quite up to par; Mediocre HD video quality; No built-in flash (but a small external flash is included).