It's hard to pin down a direct competitor for the DSC-RX10 to include in our usual image quality comparisons. The closest is probably a Sony NEX with the E-mount 18-105mm F4 OSS lens fitted. When it comes to fixed-lens cameras, it's only the Olympus Stylus 1, which (with an MSRP of $699) offers a rather less expensive take on the premium superzoom concept - albeit with less ambition. And, to demonstrate that it's really not even close to the RX10 (refer to the intro page for why), we've included the Panasonic FZ200.
As we say, the nearest realistic competitor to the RX10 would be the likes of the Sony NEX-6 (which we're having to use as a proxy for the recently-announced a6000), which can be equipped with an 18-105mm F4 lens. Another option, perhaps, might be the Nikon D5300, to which you can attach an 18-140mm lens (albeit with an F3.5-5.6 aperture range). The previous two cameras have APS-C sensors and have MSRPs of $1249 and $1399 (with lens), respectively.
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. In our tests we found that measured ISOs from the DSC-RX10 are approximately 1/3 stop under-sensitive, meaning ISO 125 indicated = ISO 100 measured.
Noise and Noise Reduction (JPEG)
ISO range noise comparison
For the noise test below we've included the Sony Alpha NEX-6, and Nikon D5300 and Panasonic Lumix DMC-FZ200. Keep in mind that, unless the NEX-6 and D5300 equipped with high-end lenses, the ISO will increase sooner than on the RX10 and FZ200.
Noise levels on the RX10 stay low until you pass ISO 3200, at which point they start to increase. Looking at the chart it seems as if the RX10 has a lot less noise than the NEX-6 and D5300 (which have much larger sensors), but that's simply because the Sony is applying a lot of noise reduction, so there's less grain-style noise (at the expense of detail). The FZ200 is never close to the RX10, which isn't surprising given its 1/2.3" sensor.
Things become more clear when you switch over to Raw. As you can see, the RX10 is a lot closer to the two APS-C cameras, especially the NEX-6. The FZ200 is considerably worse than the RX10, as one would expect.
Something else worth mentioning is that when you throw the Sony RX100 II into the widget, the RX10 is the noisier of the two, despite using the same sensor (but different image processor).
Noise reduction modes
There are three JPEG noise reduction modes on the RX10: off, low, and normal. The default, as you might have guessed, is normal. Below you can compare noise levels at each of these settings.
No real surprises here: the RX10's noise reduction at its default 'Normal' setting is very strong, so you end up nearly no visible noise until the very highest sensitivities. Of course, that comes at the cost of fine detail, as you can see from the crops. The 'low' setting is a decent compromise, but you'll want to stay well away from turning NR off entirely.
Our Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (98 CRI). A single shot of this produces a gray scale wedge from the camera's clipped white point down to black (example below). Each step of the scale is equivalent to 1/3 EV (a third of a stop), we select one step as 'middle gray' (defined as 50% luminance) and measure outwards to define the dynamic range. Hence there are 'two sides' to our results, the amount of shadow range (below middle gray) and the amount of highlight range (above middle gray).
To most people highlight range is the first thing they think about when talking about dynamic range, that is the amount of highlight detail above middle gray the camera can capture before it clips to white. Shadow range is more complicated; in our test the line on the graph stops as soon as the luminance value drops below our defined 'black point' (about 2% luminance) or the signal-to-noise ratio drops below a predefined value (where shadow detail would be swamped by noise), whichever comes first.
In the DR comparison we again have the NEX-6 and D5300, but have replaced the Panasonic FZ200 with the Olympus Stylus 1.
With its DRO feature turned off, the RX10 has a pretty standard tone curve, with a smooth roll-off in the highlights. The dynamic range is better on the APS-C cameras which, again, isn't surprising given their sensor size advantage. While it looks like the Stylus 1 has a ton of shadow detail, in reality it does not - the image is so noisy that true black is never reached.
DRO (Dynamic Range Optimization) is an adaptive algorithm that brightens the dark regions of images to give a more balanced result while retaining local contrast. Our test chart doesn't tell the whole story, as in the real world the camera breaks an image down into smaller areas, adjusting the tone curve for each.
The DRO feature does exactly what it's supposed to: it pulls up the shadows, without affecting the highlights. Between DRO Off and Level 5 you can gain over a stop of shadow detail. In real world use, we found that the DRO Auto setting was suitable in almost all situations.
While the base ISO of the DSC-RX10 is 125, you can also drop down to 80 or 100. The camera lets you know when you're in these 'low' modes by underlining the number in the menus. The point of these low ISO modes is to capture more shadow detail. But at what cost?
As you can see, you gain very little shadow tone (1/3 of a stop at most) by lowering the ISO to 80 or 100. The trade-off is losing a full stop of highlights, so you'll only want to use these 'low' settings in specific situations.