Fujifilm X-M1 Dynamic Range (JPEG)
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.
At its lowest, DR 100% setting, the X-M1 has a fairly high-contrast response, meaning that highlights clipping to white a little less smoothly than they would on some of its peers. The effect isn't overly dramatic - Canon takes a very similar approach. However, the camera's Dynamic Range modes make it easy to capture more highlight information, with a smoother transition to clipped.
Dynamic Range Modes
Moving beyond DR 100% - as we've demonstrated above - expands the range of captured highlight tones, then combined into the camera's JPEGs. At DR 200%, the camera is set to capture an extra stop of highlight dynamic range, with a risk of a fraction more shadow noise. At this point, the X-M1 offers a similar level of dynamic range to its peers.
Turn the camera up again to DR 400% and, with the added risk of low image contrast, the X-M1 is able to capture and convey a very high level of dynamic range from a single exposure. It's not something you're want to regularly use, but it's a handy feature to be able to access (especially if you're shooting JPEGs).
Dynamic range in the real world
The DR Correction feature on the X-M1 works differently than the highlight and shadow adjustments mentioned above. Without going into the gory details (which you can read about here, if you'd like), the X-M1 is able to increase the highlight range by one or two stops by raising the minimum sensitivity.
The base setting of DR100% is your only choice at the camera's native ISO of 200. Raising the DR to 200% will increase the minimum ISO to 400 in such a way that it can capture and extra stop of detail in the highlight. DR400% gives you two stops, with the minimum sensitivity set to 800. Shooting Raw images at ISO 800 / DR400% is handy, as you can reduce the dynamic range setting if your photos are looking a bit too low-contrast. You can't do the opposite, though - it's downward only.
Here's what adjusting the DR settings look like in the real world:
ISO 800, 1/400 sec, f/6.4
The most obvious improvement that comes with increasing the DR setting (visible even at this greatly reduced scale) is the return of the blue sky, as well as a building on the left side. If you view the full size images, you'll notice that the hair on the woman in the striped shirt is much more detailed at DR400%.