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ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. The 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. (Note that noise values indicated on the graphs here can not be compared to those in other reviews). Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Sony DSLR-A200 vs. Nikon D60 vs Canon EOS 1000D vs. Olympus E420

  • Sony DSLR-A200: Minolta 50 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR Off (default), JPEG Large / Fine

  • Nikon D60: Nikkor 50 mm F1.8 lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), JPEG Large / Fine
     
  • Canon EOS 1000D: Canon 50 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR Off (default), JPEG Large / Fine
     
  • Olympus E-420: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine
Sony DSLR A200
ISO 100
Nikon D60
ISO 100
Canon EOS 1000D
ISO 100
Olympus E420
ISO 100

Sony DSLR A200
ISO 200
Nikon D60
ISO 200
Canon EOS 1000D
ISO 200
Olympus E420
ISO 200

Sony DSLR A200
ISO 400
Nikon D60
ISO 400
Canon EOS 1000D
ISO 400
Olympus E420
ISO 400

Sony DSLR A200
ISO 800
Nikon D60
ISO 800
Canon EOS 1000D
ISO 800
Olympus E420
ISO 800

Sony DSLR A200
ISO 1600
Nikon D60
ISO 1600
Canon EOS 1000D
ISO 1600
Olympus E420
ISO 1600

Sony DSLR A200
ISO 3200
Nikon D60
ISO 3200
   

   

The differences in performance between the cameras in this comparison are only marginal at low sensitivities (only the E-420 is visibly softer than its counterparts) but from ISO400 upwards the different processing strategies become more apparent. At ISO 400 chroma and luminance noise starts to become visible in the Sony crops although at the same time the camera manages to maintain relatively good detail.

At very high sensitivities the noise reduction is much more heavy-handed resulting in visible smearing of fine detail without really eliminating the noise. You end up with a large amount of fairly unpleasantly intrusive blurred chroma noise blotches. In this comparison the EOS1000D delivers arguably the best balance between image detail and noise reduction.

Noise graphs

Luminance noise graph

While the A200 does fairly well against the competition in terms of measured luminance noise chroma noise is marginally higher than on some competing models. Of course the measured noise levels depend to a large extent on the amount of noise reduction applied by the JPEG engine and the crops above show that some of the cameras apply varying levels of noise reduction.

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

Chroma (color) noise graph

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

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