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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 (i.e. ISO 200, 1/200 sec for consistency of exposure between cameras). The image sequence is run through our own proprietary noise measurement tool (version 1.4 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.

Nikon D3X vs. Canon EOS 1-DS Mark III vs. Sony DSLR-A900 vs. Nikon D3

  • Nikon D3X: Nikkor 85 mm F1.8 lens, Manual exposure, Manual WB,
    Default Parameters (Normal), High ISO NR (Default: Normal), JPEG Large / Fine
     
  • Canon EOS-1Ds Mark III: Canon 85 mm F1.8 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR (Default; Off), JPEG Large / Fine
     
  • Sony DSLR-A900: Sony 85 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR (Normal - default), JPEG Large / Fine
     
  • Nikon D3: Nikkor 85 mm F1.8 lens, Manual exposure, Manual WB,
    Default Parameters (Normal), High ISO NR (Default: Normal), JPEG Large / Fine 

Nikon D3X
ISO 50
(L1.0)

Canon EOS-1Ds Mk III
ISO 50
(L)
Sony DSLR-A900
n/a
Nikon D3
n/a

Nikon D3X
ISO 100

Canon EOS-1Ds Mk III
ISO 100
Sony DSLR-A900
ISO 100
Nikon D3
ISO 100

Nikon D3X
ISO 200
Canon EOS-1Ds Mk III
ISO 200
Sony DSLR-A900
ISO 200
Nikon D3
ISO 200

Nikon D3X
ISO 400
Canon EOS-1Ds Mk III
ISO 400
Sony DSLR-A900
ISO 400
Nikon D3
ISO 400
Nikon D3X
ISO 800
Canon EOS-1Ds Mk III
ISO 800
Sony DSLR-A900
ISO 800
Nikon D3
ISO 800

Nikon D3X
ISO 1600
Canon EOS-1Ds Mk III
ISO 1600
Sony DSLR-A900
ISO 1600
Nikon D3
ISO 1600

Nikon D3X
ISO 3200
(H1.0)
Canon EOS-1Ds Mk III
ISO 3200
Sony DSLR-A900
ISO 3200
Nikon D3
ISO 3200

Nikon D3X
ISO 6400
(H2.0)
Canon EOS-1Ds Mk III
n/a
Sony DSLR-A900
ISO 6400
Nikon D3
ISO 6400

At lower sensitivities - up to ISO 400 - all four cameras in this comparison deliver excellent images with noise at a level that is pretty much negligible. As we climb higher up the ISO ladder we see more and more noise creeping in and with it the manufacturers' different approaches to noise reduction become visible.

Nikon sticks to its tried and tested combination of light luminance and comparatively strong chroma noise reduction which means that graininess starts to creep in at higher ISO settings. However, the images maintain a lot of sharpness and detail and the grainy look is quite 'film-like' and therefore acceptable to most viewers. Sony is much more heavy handed on luminance noise and applies a lot of chroma noise reduction as well. The result is heavy blurring of fine detail and fairly unpleasant smeared chroma noise blotches at higher ISOs. The difference between the D3X and the Sony A900 output is quite interesting considering the cameras' sensors are very similar (Nikon tells us it's not exactly the same sensor but they are based on the same technology). Yet the resulting JPG images have very different characteristics.

The Canon EOS-1Ds Mark III 'only' offers a maximum sensitivity of ISO 3200 but does a good job at higher sensitivities. Compared to the D3X there is slightly more chroma noise in the image but detail is preserved very well. Please also note that the Canon's noise reduction is switched off by default.

For comparison purposes we've also included the Nikon D3. Due to its lower sensor resolution and therefore larger individual photo sites the D3 has to deal with much less 'base level' noise than the higher resolving cameras in this test. There is visibly and measurably less noise in the D3 output but nevertheless the image characteristics are, unsurprisingly, very similar to the D3X.

Considering the D3X sports the most pixel-dense full frame sensor currently on the market, its high ISO performance is pretty impressive. We've seen it on previous models and the D3X confirms again that Nikon has mastered the art of noise reduction (on-chip and in processing) and completely removed (reversed, even) the advantage Canon had for so long.

Noise graphs

The D3X's measured noise increases in a fairly linear way as you move up the sensitivity scale but the curve gets visibly steeper as you pass the ISO 1600 mark. The D3X is slightly ahead of the pack in terms of gray luminance noise (which confirms what we can see in the samples above) but all in all in all there is not an awful lot of difference between the measured results of the three 20+ MP cameras in this test (the D3 unsurprisingly beats them all by a margin). Nevertheless, as we can see above, the real-world results can be very different.

Luminance noise graph (gray patch)

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

Luminance noise graph (black patch)

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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