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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.

Samsung Pro815 vs Panasonic DMC-FZ30

  Samsung Pro815
ISO 50
Panasonic DMC-FZ30
ISO 80
Crops
  Samsung Pro815
ISO 100
Panasonic DMC-FZ30
ISO 100
Crops
  Samsung Pro815
ISO 200
Panasonic DMC-FZ30
ISO 200
Crops
  Samsung Pro815
ISO 400
Panasonic DMC-FZ30
ISO 400
Crops

It doesn't take much to see how much noisier the Pro815's results are than the FZ30 at ISO 200 and 400, though this is almost entirely down to the relatively light noise reduction used by Samsung, compared to the excessive noise reduction employed by Panasonic, which smudges a lot of detail and produces the characteristic 'watercolor' effect.

Luminance noise graph

Cameras compared:
Fujifilm FinePix S9500; Panasonic DMC-FZ30; Samsung Pro 815, Canon EOS Rebel XT

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

The Pro815 has very high shadow noise at all ISO settings, but it is particularly strong at ISO 200 and 400 - again this is more an indication of the low-ish noise reduction used than the performance of the sensor itself.

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 similar to the FZ30 at low ISO settings, but rises rapidly at ISO 200 and over.

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