Panasonic Lumix DMC-GX1 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.
The GX1 uses a tone curve that is virtually identical to that of the G3, yielding approximately three stops of highlight dynamic range from middle grey to clipped white, with a more abrupt transition from bright highlights to blown-out detail than we see from rivals like the Olympus PEN and Sony NEX cameras. The APS-C cameras used in the latter company's offerings also produce roughly one additional stop of highlight data.
In these particular controlled tests, Panasonic's iDynamic mode doesn't have any obvious effect, as the camera is unable to 'analyze' the scene. In real-world shooting, iDynamic's effect is relatively subtle as well, lifting the shadows slightly but doing essentially nothing to tame the highlights. You can see image comparisons describing this behavior in more detail on our photographic tests page of this review.
The GX1, like the G3 and GF3 before it, has five 'Photo Style' color response presets in addition to its default standard mode. Of interest here is that two of these presets yield a different scene brightness at the same camera-reported exposure. 'Natural' and 'portrait' modes produce a brighter image than all other modes with middle gray rendered with approximately 1EV more luminance. As you can see, these deviations in brightness do not extend in any meaningful way to extreme highlights or shadows. Effective dynamic range remains unchanged.
What all this means in in daily use is that photographing the same scene, with the camera displaying identical exposure values, will result in images of different brightness levels based on which Photo Style has been selected. You can see real-world examples of this in our features page of this review.