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ISO / Sensitivity accuracy

The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. This gives a measure of standard output specification (SOS) sensitivity according to the ISO12232:2006 standard. We estimate the accuracy of these results to be +/- 1/6 EV.

Indicated
ISO value
Ricoh A12 50mm
measured*
Leica X1
measured*
Canon G11
measured*
Panasonic GF1
measured*
ISO 100
-
100
80
125
ISO 200
200
200
160
250
ISO 400
400
400
320
500
ISO 800
800
800
640
1000
ISO 1600
1600
1600
1250
2000
ISO 3200
3200
3200
2500
4000

* Approximate values, default settings.

The GXR with the A12 50mm camera module is pretty accurate about its indicated ISOs, as is the Leica X1. As we've noted in previous reviews, the GF1 is about a third of a stop more sensitive than indicated, rendering brighter images for any given exposure, and the G11 roughly one third of a stop less sensitive (therefore giving darker images).

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.

Ricoh GXR/A12 50mm vs. Leica X1 vs. Canon G11 vs Panasonic GF1

  • Ricoh GXR/A12 50mm: Manual Exposure, Manual WB,
    Default Parameters, High ISO NR default (Off), JPEG Large / Fine
     
  • Leica X1: Manual Exposure, Manual WB, Default Parameters (Standard), JPEG Super Fine
     
  • Canon Powershot G11: Aperture Priority, Manual WB, Default Parameters (Standard),
    JPEG Large / Fine

  • Panasonic DMC-GF1: Olympus 50 mm F2.0 Macro lens (via adapter), Manual Exposure,
    Manual WB, Default Parameters, Noise Reduction Standard (0), JPEG Large / Fine
  Ricoh GXR/A12 50mm Leica X1 Canon G11 Panasonic GF1
ISO 100  
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

The Ricoh and Leica are built around a very similar sensor and therefore it's not too much of a surprise that the noise characteristics of the two cameras are not entirely dissimilar. On the Ricoh first signs of noise are visible from ISO 400 upwards but never become really intrusive (the Leica shows a bit more). Both cameras apply a very well balanced noise reduction mix. Even at the highest ISOs there is hardly any visible chroma noise. In contrast the less intrusive (because more film-like) luminance noise is much more visible. This way a lot of image detail can be maintained up to the very highest ISO settings.

The Canon and Panasonic both have very different noise characteristics to the Ricoh and Leica. The G11 output is comparatively clean but looking at the crops it's obvious that this is achieved through very heavy-handed noise reduction, resulting in a significant loss of detail at ISO 800 and higher. The Canon is not doing badly, considering it has a much smaller sensor than the other cameras in this comparison but it is clear it cannot keep up with the APS-C or Micro Four Thirds competition. The Panasonic shows a comparable amount of detail to the Ricoh and Leica and there is also very little chroma noise but the luminance noise on the GF1 is much more intrusive. The difference is visible from ISO 400.

All in all the Ricoh's combination of sensor and JPEG engine is doing a very decent job. Its high ISO performance is on par with some of the best APS-C DSLRs (although those usually offer a higher maximum sensitivity) and amongst the very best mirrorless large-sensor cameras.

Noise graphs

The graphs below confirm more or less what we've seen the crops above. The Canon G11 measures very low noise levels but from the crops we know that is is being achieved through very heavy-handed noise reduction. The Ricoh is on the same level as the Canon but what the graphs don't show is that it preserves significantly more detail. The Leica is not too far off the Ricoh and the GF1 is the noisiest camera at almost all sensitivities.

  Ricoh GRX/A12 50mm
Chroma
Black
Gray
Measured ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.

RAW noise

Finally let's take a look a the A12 module's RAW output next to the competition. Removing any in-camera noise reduction and processing the images using Adobe Camera Raw (V5.6 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.

With noise reduction turned off we get a more accurate idea of how noisy these sensors are and the image looks slightly different to what we've seen above in the JPEG section of this page. In the RAW comparison the Ricoh and Leica are again quite close terms of both noise and detail. However, the slight noise blurring in the Ricoh image leads us to wonder whether there is some noise reduction going on in the imaging pipeline before the RAW output is generated. Without any noise reduction it becomes clear that the Canon G11 is by far the noisiest of thecameras, followed by the Panasonic GF1.

  Ricoh GXR/A12 50mm RAW Leica X1 RAW Canon G11 RAW Panasonic GF1 RAW
ISO 100  
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

Raw Noise graphs

Again the graphs confirm what we can see in the sample crops. Ricoh and Leica are on a similar level, the Canon and Panasonic both generate more image noise at higher ISOs.

  Ricoh GXR/A12 50mm
Chroma
Black
Gray
Measured ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.
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