Canon xTi, Nikon 5000 and Olympus E-620 ISO comparison
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A new ISO comparison between the three cameras shows the worse HIGH-ISO results from the Olympus E-620 compared to Nikon and Canon. But remember this are studio tests! In the real world the Olympus has a in BODY-IS which allows you to take shots at lower ISO (Nikon or Canon users have to spend a lot of money for stabilized lens).
See the comparison at cameralabs.com