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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. 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 (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.

Nikon Coolpix P5000 vs Canon PowerShot G7 vs Panasonic Lumix LX2

Nikon Coolpix P5000
ISO 64
Canon PowerShot G7
ISO 80
n/a
 
Nikon Coolpix P5000
ISO 100
Canon PowerShot G7
ISO 100

Panasonic LX2
ISO 100

Nikon Coolpix P5000
ISO 200
Canon PowerShot G7
ISO 200

Panasonic LX2
ISO 200

Nikon Coolpix P5000
ISO 400
Canon PowerShot G7
ISO 400

Panasonic LX2
ISO 400

Nikon Coolpix P5000
ISO 800
Canon PowerShot G7
ISO 800

Panasonic LX2
ISO 800

Nikon Coolpix P5000
ISO 1600
Canon PowerShot G7
ISO 1600

Panasonic LX2
ISO 1600

Nikon Coolpix P5000
ISO 2000
n/a n/a
   

Not a lot to say here that we've not already said about every other camera that uses this sensor; the noise levels are low and detail retention good at ISO 100-400, after that the combined effects of strong chroma noise reduction (with the associated color smearing) and noise get gradually worse.

With tiny, high pixel count chips noise is always going to be an issue, and to a large degree this is more a test of the effectiveness (both measurable and visible) of a camera's noise reduction system. Designers have to balance the desire to produce smooth, clean results with the need to retain as much detail as possible (if you blur away the noise, you blur away image detail too). These crops show that all manufacturers find it difficult to produce an acceptable result at anything over base ISO from 10 million pixels crammed into a tiny sensor. Minor differences in the appearance of the NR aside, the P5000 looks very similar to the Canon G7 (though luminance noise is higher at the highest ISO settings).

Low contrast detail

What the crops and graph don't show is the effect of noise reduction on low contrast fine detail such as hair, fur or foliage. An inevitable side effect of noise removal is that this kind of detail is also blurred or smeared, resulting in a loss of 'texture'. In a new test the crops below show the effect of the noise reduction on such texture (hair) as you move up the ISO range.

100% Crops
ISO 64 ISO 100 ISO 200 ISO 400
ISO 800 ISO 1600 ISO 2000 ISO 3200

The good news is that the P5000's light touch with luminance NR means that it's ability to retain fine, low-contrast detail is better than many of its competitors (including the G7), though this does come at the expense of slightly more visible noise in the ISO 400+ region. Hats off to Nikon for getting the balance of detail and noise reduction as good as it can be in a camera with this sensor. ISO 3200 (5MP size) is noise - and detail - free.

Luminance noise graph

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

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 are on the vertical axis.

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