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 (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.

Note: this page features our 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

Here we look at how the LX100's default tone curve compared to its immediate peers.

The LX100's default tone curve gives-over a good amount of space to highlight information. If you look at the RX100 III, you can see it has a relatively steep, high-contrast response above middle grey, then a pronounced roll-off to a low-contrast region as you get to the very brightest tones. This has the effect of smoothing the transition from near-white to clipped white regions, which can stop clipped areas looking too jarring.

Instead the LX100 uses a lower-contrast tone curve all the way up to clipping, which means that, although it captures 2/3EV more highlight information than the Sony, its clipped highlights may appear more obvious when you look at their images side-by-side.

DR Modes

The LX100 uses the same i.Dynamic feature as other recent Panasonics. i.Dynamic can do two things in response to detecting high contrast scenes. The first process uses a series of different tone curves to boost the mid-tones and shadows to try to give a better balanced image. The second is that it can reduce exposure slightly, in order to capture more highlight information.

Shot in aperture priority mode, so that the camera can adjust the exposure, you can see that the tone-curve pushes are much more dramatic than the exposure adjustment aspect of the mode. In fact you can see that in this case i.Dynamic hasn't actually applied any adjustment to exposure (which you'd see as a rightward shift at the top right of the graph). Instead we just see the mid-tones and shadows being increasingly brightened.

Making the most of i.Dynamic

However, with this understanding of how dramatic i.Dynamic modes' tone curve pushes are, you can manually apply your own exposure correction to make better use of them:

By manually applying negative exposure compensation when you shoot, you can force the camera to capture additional highlight information. Then, by combining this exposure compensation with an appropriate i.Dynamic mode, you can ensure that the mid-tones of your image are correctly represented in the JPEG.

Exposure reduction required to capture highlights i.Dynamic setting
-0.3EV
Low
-1EV
Standard
-1.7EV
High

We'd recommend doing this in Manual exposure mode, so that i.Dynamic mode can't try to apply any additional, unexpected exposure corrections of its own.

Any attempt to increase highlight capture by reducing exposure will always come at the cost of some increased noise, so we'd always recommend using the minimum amount of exposure reduction and i.Dynamic required to capture the desired amount of highlight information.