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. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). Note that these tests are based on the sRGB JPEG output of the cameras, in accordance with ISO 12232:2006, the standard used by camera manufacturers.
By our tests, the E-P3's measured sensitivities are about 1/6 stop lower than indicated (i.e. images are fractionally darker than expected for any given set of exposure values), which is within the tolerance allowed by the ISO specification.
Noise and Noise Reduction (JPEG)
Note: this page features our new interactive noise comparison widget. By default, we show you the default noise reduction settings of the camera tested, and three other models of the same class. You can select from all available NR options, and from other cameras. The 'tricolor' patches beneath the familiar gray/black/portrait images are taken from the same test chart, and show how noise impacts upon blue, green and red areas of a scene.
ISO range noise comparison
The E-P3 uses the latest variant of the stalwart Panasonic 12MP LiveMOS Four Thirds sensor, and offers no great surprises in terms of noise performance. As we've become accustomed to from Olympus, its JPEG processing does a reasonably good job of balancing noise and detail, and provides highly presentable results up to ISO 1600; above this, the image quality starts to deteriorate rapidly, with ISO 6400 not pretty at all and ISO 12800 practically unuseable. This means it can't quite match the high ISO performance of newer sensors, such as the Panasonic G3's 16MP Four Thirds chip or the APS-C competition.
Looking at the graphs, though, it's clear that Olympus has made some advance over previous PENs; while the chroma and luminance noise lines are identical to older cameras such as the E-PL1, the black noise shows a clear improvement. This doesn't have a huge visual impact in these crops, but should in principle make for cleaner-looking JPEGs at the highest sensitivities.
JPEG Noise reduction settings
The E-P3 has four JPEG noise reduction settings, accessed via the 'Noise Filter' option in the Custom Menu G (the 'Noise Reduction' option is for long exposures). These provide a range of options to balance noise against detail to your own personal taste. The default 'Standard' setting gives a somewhat smoothed-over, plastic look especially at high ISOs, and we think the best results come with the Noise Filter Turned down a notch or two, to Low or even Off. We'll look into this in more detail leter in the review.
RAW noise (ACR 6.5 - noise reduction set to zero)
Here we look at the RAW files processed through Adobe Camera Raw (in this case version 6.5). Images are brightness matched and processed with all noise reduction options set to zero.
Adobe does a degree of noise reduction even when the user-controlled NR is turned off. The amount of NR applied 'under the hood' is not high, but it does vary by camera (Adobe is attempting to normalize output across different sensors), so inevitably we are still looking at a balance of noise and noise reduction, rather than pure noise levels. However, the use of the most popular third-party RAW converter is intended to give a photographically relevant result, rather than simply comparing sensor performance in an abstract manner.
The similarity of both the figures and the appearance of these crops suggests they tell us as much about Adobe's ability to normalize the various cameras' outputs as about the cameras themselves. Nevertheless we can see that the E-P3's sensor produces noisier output than either the Panasonic G3's or the APS-C competition. Comparison to other Olympus cameras shows that the lower black noise in the JPEG graphs is purely a result of improved in-camera processing - the raw results are essentially the same as the E-PL2's, for example. So there's no incentive for owners of older PENs to upgrade on this account alone.