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-LX2 vs Nikon Coolpi P3 vs Ricoh GR-D (ISO 50-400)

n/a	Nikon Coolpix P3 ISO 50	Ricoh GR-D ISO 64
Panasonic DMC-LX2 ISO 100	Nikon Coolpix P3 ISO 100	Ricoh GR-D ISO 100
Panasonic DMC-LX2 ISO 200	Nikon Coolpix P3 ISO 200	Ricoh GR-D ISO 200
Panasonic DMC-LX2 ISO 400	Nikon Coolpix P3 ISO 400	Ricoh GR-D ISO 400

Panasonic LX2 High ISO settings (ISO 800 and 1600)

	Panasonic DMC-LX2 ISO 800	Panasonic DMC-LX2 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).

Everything we said about the FZ50 applies here; yes the Venus III processor produces measurably lower noise, it does so at the expense of fine detail; particularly chroma information, which is smeared away at anything over ISO 100 if you use the default noise reduction setting (as here).

Luminance noise graph

Cameras compared:
Panasonic DMC-LX2, Canon PowerShot S80, Ricoh GR-D
Note: ISO 50-1600 only (the LX2'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. To see this graph 'zoomed' to show only ISO 50-400 click here.

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 LX2 has very low noise compared to its competitors - 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. To see this graph 'zoomed' to show only ISO 50-400 click here.

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