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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 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 1.5 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.)

Panasonic DMC-FZ50 vs Canon PowerShot S3 IS vs Panasonic DMC-FZ7

n/a Canon PowerShot S3 IS
ISO 50

Panasonic DMC-FZ30
ISO 80

 

Panasonic DMC-FZ50
ISO 100
Canon PowerShot S3 IS
ISO 100
Panasonic DMC-FZ30
ISO 100

Panasonic DMC-FZ50
ISO 200
Canon PowerShot S3 IS
ISO 200
Panasonic DMC-FZ30
ISO 200

Panasonic DMC-FZ50
ISO 400
Canon PowerShot S3 IS
ISO 400
Panasonic DMC-FZ30
ISO 400

Panasonic FZ50 High ISO settings (ISO 800 and 1600)

  Panasonic DMC-FZ50
ISO 800
Panasonic DMC-FZ50
ISO 1600
Crops

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).

It's interesting to compare the FZ50 (with it's Venus III engine) and its predecessor the FZ30. Noise is visibly lower, but (using the default NR setting as here) you're sacrificing even more detail, producing results that - though very clean and smooth - are actually softer looking and less detailed, despite the extra two million pixels. As our studio shot shows, with good light and fairly contrasty detail, detail is actually fairly well preserved even at ISO 400 (the luminance NR is quite low), but once you get low contrast fine detail you can see the effect of the heavy chroma NR even at ISO 100.

Luminance noise graph

Cameras compared:
Panasonic DMC-FZ50, Canon PowerShot S3 IS, Panasonic DMC-F30
Note: ISO 50-1600 only (the FZ50's ISO 3200 mode uses pixel-binning and is not full resolution).

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

As usual what we're really looking at here isn't 'noise' as much as noise reduction, and - as we've seen from visual assessment of the files - the FZ50 has very low noise compared to its competitors (and particularly in comparison with its predecessor the FZ30) - especially at higher ISO settings.

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.

As the graph shows, chroma noise nose-dives at ISO 400 when the Venus III smearing really kicks in.

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