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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 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 (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.)

Fuji FinePix F50fd vs FinePix F31fd vs Nikon Coolpix P5100

Fuji FinePix F50fd
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Fuji FinePix F31fd
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Nikon Coolpix P5100
ISO 64
Fuji FinePix F50fd
ISO 100
Fuji FinePix F31fd
ISO 100
Nikon Coolpix P5100
ISO 100
Fuji FinePix F50fd
ISO 200
Fuji FinePix F31fd
ISO 200
Nikon Coolpix P5100
ISO 200
Fuji FinePix F50fd
ISO 400
Fuji FinePix F31fd
ISO 400
Nikon Coolpix P5100
ISO 400
Fuji FinePix F50fd
ISO 800
Fuji FinePix F31fd
ISO 800
Nikon Coolpix P5100
ISO 800
Fuji FinePix F50fd
ISO 1600
Fuji FinePix F31fd
ISO 1600
Nikon Coolpix P5100
ISO 1600
Fuji FinePix F50fd
ISO 3200
Fuji FinePix F31fd
ISO 3200
Nikon Coolpix P5100
ISO 3200
Fuji FinePix F50fd
ISO 6400
Fuji FinePix F31fd
n/a
Nikon Coolpix P5100
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Fujifilm's 6 MP Super-CCD Sensor was doing a brilliant job in the F31fd, and it was always going to be a hard act to follow. The F31fd offered amazingly low noise levels at ISO 100-400, and at ISO 800 / ISO 1600 it was way above the competition, providing both lower noise and better detail retention. Although visibly noisier (viewed at 100%) than the F31fd, the F50fd's new Super-CCD sensor doubles the pixel count to 12MP and still manages to outperform conventional CCDs - though the gap has narrowed.

Of course it's far from perfect; there's strong chroma noise at anything over ISO 400 and the effects of luminance noise and noise reduction mean that ISO 800 and above are nowhere near as clean as the F31fd. The jump from 6 to 12 megapixels appears to have virtually no benefit (except, perhaps if you're a memory card vendor) once you get beyond ISO 400.

That all said, and putting aside comparisons to the F31fd for a moment, there's no denying that Super-CCD's (and Real Photo Processor's) performance looks very impressive when compared to a 'standard' sensor camera such as the Nikon P5100. The Nikon has no chance of keeping up with the F50fd from ISO 200 upwards and even at ISO 400 the gap can be described as significant.

Luminance noise graph

Cameras compared:
Fujifilm FinePix F50fd, Fujifilm FinePix F31fd, Nikon Coolpix P5100

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

As seen in our test shots above, the F50fd produces marginally higher levels of luminance noise than its predecessor at all sensitivity settings, with the gap staying even througout the ISO range. The Nikon has lower noise levels than the F50fd below ISO 800 but this is largely paid for by a significant loss of detail caused by the processor's noise reduction algorithms.

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.

For chroma noise the picture is almost identical to our luminance noise analysis, higher levels on the FD50fd than on the F31fd, with noise shooting up from ISO1600 upwards. Up to ISO400.

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 this 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 100 ISO 200 ISO 400
ISO 800 ISO 1600 ISO 3200
   
ISO 6400    

Firstly it's obvious that Fuji has had to get a lot more heavy handed with the noise reduction on this camera than it did on the F31fd, and viewed at a pixel level the output isn't that pretty at anything over base ISO. As you would expect both noise and low contrast smearing (caused by noise reduction) increase throughout the ISO range.

That said, at up to ISO400 there is still plenty of texture and the noise levels are acceptable. From ISO800 upwards noise reduction becomes much more aggressive and chroma noise really starts to get unpleasant. ISO 3200 and 6400 are firmly positioned in the emergency zone. In summary, while at a pixel level the F50fd can't outperform the leader in this area (the F31fd) it certainly retains higher levels of detail with lower noise in the key ISO 200-800 range than most comparable cameras.

Fujifilm F31fd vs F50fd @ 6MP

One of the claims made by Fujifilm in its early marketing material on the F50fd was that at higher ISO settings it offers the same quality as its illustrious predecessor - at 6MP (in other words comparing like for like). To test this we have reduced the image size of ISO 800 and ISO 1600 F50fd test shots (12MP, 4000 x 3000 px) to the dimensions of a 6MP F31fd picture (2848 x 2136 px). Photoshop's 'Bicubic Sharpener' setting was used for resampling. We have also included an original size crop for comparison. Let's have a look at the results.

ISO 1600 downsized ISO 1600 full size ISO 800 downsized ISO 800 full size

The test crops show pretty clearly that, while the 100 percent F50fd image is a lot softer than its predecessor's, a downsampled (and sharpened) version is pretty close to the F31fd's output. But the sad fact is that the F50fd is struggling to match the F31fd (the output is noisier and less clean). There's perhaps a touch more texture retained in the F50fd version, and the noise reduction is a little less heavy-handed, but overall the effect is less pleasing.

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