JPEG tone curves / dynamic range

Our Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (95 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.

Note: this page features our new interactive dynamic range comparison widget. The wedges below the graph are created by our measurement system from the values read from the step wedge, the red lines indicate approximate shadow and highlight range (the dotted line indicating middle gray).

Cameras Compared

Our comparison chart shows the RX100 II's default tone curve has a fairly typical S-curve with a little less than a stop advantage at the top of the highlight range over the Canon G1 X. Since the RX100 is still being sold alongside the RX100 II we've included it in our comparison, and the two models appear to be very similar at the bottom and top of the range.

DR modes

Glancing at the chart below you'll notice that all of the RX100 II's dynamic range modes all clip highlights at about the same place. That matches up with our real-world findings, demonstrated at the bottom of the page. Highlights at the very top of the range are left untouched, while the difference between DRO off and DRO level 5 is about a full stop difference in shadow tone.

The real-world example below shows DRO in action. As shown in the graph above, DRO leaves the clipped highlights in the scene untouched. DRO level 5 applies a dramatic brightening to shadow tone, revealing detail in the upper right corner of the scene that wasn't visible with DRO turned off. Auto takes a little more conservative approach, and for this scene it appears to have chosen a correction level close to 3.

DRO Auto
DRO Level 1
DRO Level 2
DRO Level 3
DRO Level 4
DRO Level 5