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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 S100FS

Fujifilm FinePix S100FS
ISO 100

Nikon D60
ISO 100

Canon G9
ISO 100
Fujifilm FinePix S100FS
ISO 200
Nikon D60
ISO 200
Canon G9
ISO 200
Fujifilm FinePix S100FS
ISO 400
Nikon D60
ISO 400
Canon G9
ISO 400
Fujifilm FinePix S100FS
ISO 800
Nikon D60
ISO 800
Canon G9
ISO 800
Fujifilm FinePix S100FS
ISO 1600
Nikon D60
ISO 1600
Canon G9
ISO 1600
Fujifilm FinePix S100FS
ISO 3200
Nikon D60
ISO 3200
n/a
 
Fujifilm FinePix S100FS
ISO 6400
n/a n/a

Fujifilm FinePix S100FS
ISO 10000

n/a n/a

FujiFilm has put its latest, eighth-generation, Super CCD HR technology into the S100FS. This uses octagonal photosites that are designed to maximize light collecting efficiency. This, combined with clever noise reduction algorithms has helped FujiFilm develop a reputation for good low-light performance with its Super CCD-equiped cameras. The S100FS is no exception - although its sensor is only around a third larger than the Canon's, the advantages are pretty dramatic and it performs pretty admirably against the entry-level DSLR it hopes to compete with.

Interestingly, FujiFilm has taken a measured approach to noise reduction - giving excellent levels of detail in comparison to the Nikon and the Canon while allowing a tolerable amount of noise. This competitive edge is retained all the way up to ISO 800, with far greater detail making up for the S100FS's extra noise.

The Fuji doesn't really concede the battle until ISO 3200, at which point it is overcome by the Nikon's superior detail. Its heroics would be far more commendable if it then laid down its arms, rather than rampaging on to an ignominious end at ISO 10000, some 2.6 stops after the D60 has decided to hold its ground for strategic reasons.

Noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis. Noise rises as you'd expect up to ISO 1600, beyond which the noise reduction strategy must change, as the noise no longer rises in a linear fashion. Noise then appears to drop off above ISO 3200, which is exceedingly unlikely unless it denotes increasingly aggressive noise reduction is being applied.

This is exactly the pattern seen in the crops, above, with noise rising gently and without too much loss of detail until ISO 1600, followed by a sharper drop in detail to ISO 3200 before going into complete free-fall down to the be-smudged and artifact-heavy ISO 10000.

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 ISO 6400 ISO 10000

This test attempts to re-create the conditions that appear in real-world images. Whether it's grass, hair or distant plaid attire, fine detail of a similar color can easily confuse noise reduction routines, which just smear all of the results together and remove or distort fine texture in the final images.

And this is an area in which the S100FS disappoints a little. Even at its lowest settings there appears to be some noise reduction going on, so the fine detail is not resolved. This result, in such stark contrast with the results in the side-by-side test further up this page, shows that the S100FS is being selective about where it applies noise reduction. Detail with plenty of contrast isn't affected but low-contrast features are overly smoothed by noise reduction. The effects can be seen in our real-world shots in the samples gallery at the end of the review.

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