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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
Leica X1
measured*
Nikon D300S
measured*
Panasonic GF1
measured*
Canon G11
measured*
ISO 100
100
100
125
80
ISO 200
200
200
250
160
ISO 400
400
400
500
320
ISO 800
800
800
1000
640
ISO 1600
1600
1600
2000
1250
ISO 3200
3200
3200
4000
2500

* Approximate values, default settings.

The X1 is pretty well on the money for its indicated ISOs, as is the Nikon D300S. As we've noted in previous reviews, the 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.

Leica X1 vs Nikon D300S vs Panasonic DMC-GF1 vs Canon Powershot G11
JPEG Noise comparison

  • Leica X1: Manual Exposure, Manual WB, Default Parameters (Standard), JPEG 12.2M Super Fine

  • Nikon D300s: Nikkor 50 mm F1.4 G lens, Manual Exposure, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), 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. Firmware version 1.1.

  • Canon Powershot G11: Aperture Priority, Manual WB, Default Parameters (Standard),
    JPEG Large / Fine
  Leica X1 Nikon D300S Panasonic GF1 Canon G11
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

Note: The Canon G11 also has a base ISO 80 setting, which is a little less noisy than ISO 100

Here we're comparing the Leica X1 to the Nikon D300S (which pretty much defines the state-of-the-art output for this kind of 12Mp APS-C sensor), the Panasonic GF1 (representing the Micro Four Thirds contingent), and the Canon Powershot G11 with its much smaller (but 'high sensitivity') 1/1.8" sensor. The four cameras produce very similar results at low ISOs (although the X1's very 'open' tone curve is representing blacks so pale that it's actually rendering the matte surface texture of our test chart at ISO 100), but by ISO 400 the sensor on the G11 is visibly starting to struggle, with contrast and fine detail just beginning to fall away. At higher ISOs the G11, while producing impressive results for a compact, just can't keep up, smearing away all fine detail.

At ISO 1600 the X1 also starts to pull ahead of the GF1, with its slightly smaller Four Thirds sensor; at ISO 3200 the difference becomes marked (although Panasonic's light touch noise reduction is retaining a little more fine detail here). All the while, though, the D300S produces visibly cleaner results, but without overly smearing fine detail - the result of a combination of intelligent of noise reduction, and Nikon's approach of suppressing shadow noise by clipping to black much sooner.

Noise graphs

  Leica X1 vs Nikon D300S vs Panasonic GF1 vs Canon Powershot G11
Chroma
Black
Gray

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

These graphs confirm that Leica is applying some subtle noise reduction at ISO 1600 and above. Measured gray and chroma noise are near-identical between the X1 and D300S; the X1's high black noise is mainly a reflection of its unusually bright rendition of our chart's black patch. The G11 clearly applies relatively heavy noise reduction, resulting in measured noise levels that match the two APS-C cameras; in comparison the GF1 shows a relatively light touch approach to NR, leaving behind distinctly more noise at the highest ISOs.

RAW noise

Raw noise compared (ACR)

Switching to raw and converting using our benchmark developer (Adobe Camera Raw) - with all noise reduction turned off - gives us the nearest thing to a 'level playing field' for assessing the relative noise levels of the four cameras' sensors. In this comparison things divide up more or less according to sensor size, with larger of course doing better.

  Leica X1 Nikon D300S Panasonic GF1 Canon G11
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

This approach reveals just how close the X1's output comes to that of the D300S. The two APS-C cameras are neck-and-neck at all ISOs, producing visually near-indistinguishable quality. In comparison the GF1's output is noticeably noisier (especially at 1600 and 3200), although it does retain good levels of detail. The G11 really can't keep up, and although it's doing an unexpectedly good job for a compact, it's really not rendering much fine detail and the noise pattern has an unpleasant 'clumped' texture to it. Overall the conclusion has to be that when it comes to image quality, there's no substitute for sensor size.

Raw Noise graphs

  Leica X1 vs Nikon D300S vs Panasonic GF1 vs Canon Powershot G11
Chroma
Black
Gray

Measured ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis. Note: the vertical scale on this graph has been doubled compared to the other graphs in this section.

The graphs confirm the X1 is in fact more than a match for the D300S, returning slightly better results in terms of measured noise. The GF1 lags a stop or so behind the APS-C cameras, and while the G11 is doing unexpectedly well in the gray and black noise graphs, its chroma noise is comparatively much higher - and remember that looking at the crops, its retention of fine detail is the worst of the bunch. Overall, then, the conclusion has to be that the X1 is comfortably the best-performing small camera, in terms of high ISO noise, currently available.

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