ISO Sensitivity / Noise levels


Standard Test
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 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.

Fujifilm FinePix S9000 vs Canon EOS Rebel XT

  Fuji FinePix S9000
ISO 80 		n/a
Crops
  Fuji FinePix S9000
ISO 100 		Canon EOS Rebel XT
ISO 100
Crops
  Fuji FinePix S9000
ISO 200 		Canon EOS Rebel XT
ISO 200
Crops
  Fuji FinePix S9000
ISO 400 		Canon EOS Rebel XT
ISO 400
Crops
  Fuji FinePix S9000
ISO 800 		Canon EOS Rebel XT
ISO 800
Crops
  Fuji FinePix S9000
ISO 1600 		Canon EOS Rebel XT
ISO 1600
Crops

Maybe it's an unfair comparison, maybe not (after all, Fujifilm sells this as a viable alternative to a digital SLR), but it does show that up to about ISO 400 the S9000 does a far better job of controlling noise than any of its direct competitors. Above ISO 400 the difference between the S9000 and the Rebel XT are visible, and stark. Looking at the graphs below you'd think that noise levels weren't that different, but that's all down to the strong noise reduction the S9000 is employing, and the amount of detail lost is unacceptable for prints at larger sizes.

Luminance noise graph

Cameras compared:
Fujifilm FinePix S9000; Panasonic DMC-FZ30; Samsung Pro 815, Canon EOS Rebel XT

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

The S9000's noise levels - especially at the lower end of the scale - are very low, certainly for a camera in this class, and certainly when you consider the pixel density. Not bad at all!

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.

Compared to the FZ30 and the Samsung Pro 815 the S9000's chroma noise is admirably low in the 'standard' (up to ISO 400) part of the graph, though as mentioned above, ISO 800 and 1600 are only low-ish because of heavy noise reduction. Anyone hoping for FinePix F10-like performance will be disappointed by the S9000's high ISO output.