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ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. This works by turning up the "volume" (gain) on the sensor's signal amplifiers (remember the sensor is an analogue device). By amplifying the signal you also amplify the noise which becomes more visible at higher ISO's. Many modern cameras also employ noise reduction and / or sharpness reduction at higher sensitivities.

To measure noise levels we take a sequence of images of a GretagMacBeth ColorChecker chart (controlled artificial daylight lighting). The exposure is matched to the ISO (ie. ISO 200, 1/200 sec for consistency of exposure between cameras). The image sequence is run through our own proprietary noise measurement tool (version 1.5 in this review). Click here for more information. Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Olympus E-620 vs. Nikon D5000 vs. Canon EOS 500D vs Panasonic DMC-G1

  • Olympus E-620: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters, Normal Picture Mode, Gradation Normal, Noise Filter Standard, JPEG Large / Fine

  • Nikon D5000: Nikkor 50 mm F1.4G lens, Aperture Priority, Manual WB,
    Default Parameters. Standard Picture Controls, Active D-Lighting Off, NR Normal, JPEG Large / Fine

  • Canon EOS 500D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, Standard Picture Style, NR Standard, JPEG Large / Fine

  • Panasonic DMC-G1: Olympus 50 mm F2.0 Macro lens (Via adapter), Aperture Priority, Manual WB,
    Default Parameters (Normal), High ISO NR Normal, JPEG Large / Fine
  Olympus E-620 Nikon D5000 Canon EOS 500D Panasonic DMC-G1
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

There are quite high levels of sharpening being applied to the E-620's JPEGs but in terms of details, it's not far behind the Canon 500D (the camera conveying the most detail here). It falls a little further behind at ISO 800 and 1600, with fine detail being smoothed away to a greater extent than any of the other cameras here, but it's still not far behind the Nikon (itself a good performer), even then. ISO 3200 is pretty mushy but that's to be expected of anything short of a full-frame camera.

Noise graphs

  Olympus E-620
Chroma
Black
Gray

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.

The graphs show us that the E-620 is allowing slightly more chroma noise and quite a lot more noise in the blacks through into the final image, despite its relatively high default noise reduction setting. However, it's pretty close to its rivals up to ISO 800 in terms of noise - it's only 1600 an upwards that the difference is noticeable in the final images.

RAW noise

With ACR taking away any of the clever processing done by the manufacturers' JPEG engines, the E-620 is competitive all the way through the ISO range. Sure, chroma noise is pretty high at the top of the range, but that's easily removed if you don't like it.

  Olympus E-620 RAW Nikon D5000 RAW Canon EOS 500D RAW Panasonic DMC-GH1 RAW
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200


Raw Noise graphs

With noise reduction set to its lowest settings, there's a much closer relationship between measured noise and the visual appearance of that noise (because there's very little processing going on that would muddy the waters). So, as the crops above would lead you to expect, the E-620 is competing pretty convincingly with its immediate peers, all the way through the ISO range.

  Olympus E-620 RAW
Chroma
Black
Gray
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.
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