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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 1.4 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.)

Fuji FinePix S6000fd vs Canon S3IS

  n/a

Canon PowerShot S3 IS
ISO 80

Crops

  Fujifilm FinePix S6000fd
ISO 100
Canon PowerShot S3 IS
ISO 100
Crops
  Fujifilm FinePix S6000fd
ISO 200
Canon PowerShot S3 IS
ISO 200
Crops
  Fujifilm FinePix S6000fd
ISO 400
Canon PowerShot S3 IS
ISO 400
Crops
  Fujifilm FinePix S6000fd
ISO 800
Canon PowerShot S3 IS
ISO 800
Crops
  Fujifilm FinePix S6000fd
ISO 1600
n/a
Crops
 
  Fujifilm FinePix S6000fd
ISO 3200
n/a
Crops

As we saw with the F30 the noise advantage of the S6000fd is greatest in the middle of the ISO range. Few cameras have a significant noise problem at 'base' ISO (the lowest setting), and the differences between all most of them is minimal. But most small CCD cameras start to suffer from the problems of noise - and more importantly the destructive effect of noise reduction - once you get to ISO 200 or 400. Here the latest incarnation of Fuji's Super CCD sensor really shines, with ISO 400 and 800 - though still showing evidence of strong noise reduction - considerably better than any conventional CCD competitor. Interestingly - and disappointingly - the S6000fd's high ISO performance (particularly at ISO 1600 and 3200) isn't anywhere near as good as the F30, a camera with, apparently, the same sensor. The only explanation is a change in the internal processing.

Luminance noise graph

Cameras compared:
Fujifilm FinePix S6000fd, Canon PowerShot S3 IS, Sony DSC-H2

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

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 (fur) as you move up the ISO range.

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

It's only when you look at these 'real world' crops that the real advantage of the Super CCD sensor used in the S6000fd is obvious. With all small CCD compacts we see serious smearing of low contrast detail at ISO 200 (sometimes even lower), but the S6000fd manages to keep plenty of texture at ISO 400, and even ISO 800 and 1600 haven't smeared it all away (in fact the noise reduction at 800 and 1600 appears to be very similar; you just get more noise at 1600). ISO 3200 is, to put it politely, rather light on detail, and you're certainly not getting the claimed 'full resolution' ISO 3200 output. Still, it's better than anything else on the market...

Note that you'll be able to preserve a lot more low contrast detail by shooting raw at high ISO settings, but you'll then have a lot more noise to contend with.

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