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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 (i.e. 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. Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Panasonic GH1 vs Canon EOS 500D vs. Nikon D5000 vs. Olympus E-620

  • Panasonic DMC-GH1: Olympus 50 mm F2.0 Macro lens with DMW-MA1APP adapter,
    Manual exposure, Manual WB, Default Parameters (Standard), NR (0 - default), JPEG Large / Fine

  • Canon EOS 500D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), High ISO NR (Default; Standard), JPEG Large / Fine
     
  • Nikon D5000: Nikkor 50 mm F1.4G lens, Aperture Priority, Manual WB, ADL off
    Default Parameters (Normal), High ISO NR (Default; Norm) JPEG Large / Fine
     
  • Olympus E-620: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine
  Panasonic GH1 Canon EOS 500D Nikon D5000 Olympus E-620
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400    
ISO 12800      

As one would expect there is from a noise and NR point of view very little difference in real terms between any of these cameras up to ISO 400. At ISO 800 you see the first hints of chroma noise appearing on the Canon and Olympus but all cameras maintain relatively good detail.

As we go further up the ISO range noise becomes more intrusive but at its default settings the GH1's approach to noise reduction is very nicely balanced. The Panasonic algorithms apply only comparatively small amounts of luminance noise reduction but are quite heavy on the chroma noise. As a result the images retain relatively good detail up to high sensitivities. There is a fair amount of luminance noise in the GH1 high ISO output but this is far less irritating than the chroma noise color blobs we can observe on some other cameras.

The ISO 1600 and 3200 settings are no doubt quite noisy (there is now also some band-shaped chroma noise creeping in) but the GH1 retains more detail than the competition in this comparison. Depending on your quality requirements ISO 3200 is still usable for smaller prints or web galleries. All in all Panasonic's noise reduction routines are doing a good job reducing noise in a way that leads to visually pleasing results.

Noise graphs

The graphs confirm what we can see on the sample crops above. Noise on the GH1 is kept pretty flat until ISO 800 and then increases pretty quickly. However, Panasonic manages to process sensor noise in a way that makes it less visually unpleasant than on some of the competitors.

  Panasonic GH1
Chroma
Black
Gray

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

GH1 noise compared to G1

While in terms of dynamic range, resolution and detail the GH1 performs pretty much identically to its older sister model G1 Panasonic has made some noticeable improvements in the noise area. The improved performance starts to become visible (but only just) at ISO 800 but it is much more obvious at the two highest ISO settings. As you can see on the crops below at ISO 1600 and 3200 the GH1 produces less of both luminance and chroma noise than the G1 whilst pretty much maintaining the level of detail.

Panasonic GH1
ISO 1600
Panasonic G1
ISO 1600
Panasonic GH1
ISO 3200
Panasonic G1
ISO 3200

RAW noise

Finally let's take a look a the GH1's RAW output next to the competition. Removing any in-camera noise reduction and processing the images using Adobe Camera Raw (V5.4 Beta in this case, all NR set to 0) gives us the nearest thing to a 'level playing field' for assessing the relative noise levels of the four cameras' sensors.

In this RAW comparison the GH1's Four Thirds sensor does, from a noise point of view, a pretty decent job versus the larger APS-C sensors of the Canon and Nikon. With noise reduction reduced to a minimum the GH1 produces slightly more noise than the Nikon D5000 but less chroma noise than the Canon EOS 500D and Olympus E-620. All in all the differences between the cameras here are pretty small though.

  Panasonic GH1 RAW Canon EOS 500D RAW Nikon D5000 RAW Olympus E-620 RAW
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400    
ISO 12800      

Raw Noise graphs

The graphs below more or less confirm what we can see in the sample crops. However, there is a slight abnormality in the GH1 noise measurements in so far that black luminance noise decreases from ISO 400 to 800. The data in this graphs is from our usual Adobe ACR conversions but we've tried this with various RAW converters and the result is always the same. This suggests that Panasonic is performing some type of noise reduction on the RAW files but we can only speculate about this.

  Panasonic GH1
Chroma
Black
Gray
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.
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