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ISO Sensitivity / Noise levels


Standard Test
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 ISOs. 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 (i.e. ISO 200, 1/200 sec for consistency of exposure between cameras).

The image sequence is run through our own proprietary measurement tool which measures the standard deviation (normalized) of the middle gray patch (indicated by the red rectangle above). Note that noise values indicated on the graphs below should not be compared to those in other reviews.

Kodak P850 vs Panasonic DMC-FZ20

  Kodak P850
ISO 50
Panasonic DMC-FZ20
n/a
Crops
  Kodak P850
ISO 80
Panasonic DMC-FZ20
ISO 80
Crops
  Kodak P850
ISO 100
Panasonic DMC-FZ20
ISO 100
Crops
  Kodak P850
ISO 200
Panasonic DMC-FZ20
ISO 200
Crops
  Kodak P850
ISO 400
Panasonic DMC-FZ20
ISO 400
Crops

The P850 is, like all the 5MP 'super zoom' compacts we've tested, pretty noisy at the high end of the ISO range (particularly ISO 400). As the patches above show, the Kodak chip appears to have a lot more visible noise at ISO 400 than the Panasonic FZ20 (which is broadly speaking fairly representative of the current crop of 5MP super zooms). You can also see clearly the white balance shift at ISO 400 (all these shots are taken using the same custom WB setting) that we saw in the studio comparison images.

Note: we didn't test the ISO 800 setting as it is only available at the lowest 1.2 megapixel image size.

Luminance noise graph

Cameras compared:
Kodak P850, Panasonic DMC-FZ20, Olympus SP-500 Ultra Zoom

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

As the noise measurements show, the P850 has exhibits higher than average shadow noise at pretty much all sensitivities, though it's most noticeable at the high end of the ISO range. Note that all our tests indicated that the noise levels at ISO 64 were higher than at ISO 64, but lower than ISO 80, which would seem to indicate that noise reduction kicks in at ISO 80.

RGB noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of each of the red, green and blue channels is on the vertical axis.

Chroma noise is broadly similar to the other cameras in this class, though to keep it down the P850 uses some of the strongest noise reduction we've seen to date, with the result that although measurable noise is fairly low, the images look blotchy and lack detail.

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