Panasonic Lumix DMC-GF3 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 GF3 uses a tone curve that differs slightly from that of its predecessor, the GF2, yielding somewhat brighter highlight tones. It provides approximately three stops of highlight dynamic range from middle grey to clipped white. As with other Panasonic G-series models, the roll-off to the highlights is relatively steep, meaning there can be a rather abrupt transition from near-white pixels to clipped data. This behavior falls noticeably short of its APS-C competitors which show more highlight detail, with a much gentler roll-off from maximum white to near-white values. This is not a poor performance mind you, but does point to some limitations of Panasonic's venerable 12MP CMOS sensor.
In these particular controlled tests, Panasonic's iDynamic mode doesn't have any obvious effect. In real-world shooting it's relatively subtle too, lifting the shadows (at the expense of extra noise) but doing little or nothing to tame the highlights. This is disappointing compared to competitive systems like Sony's DRO and Olympus' Gradation function, to name but two.
The GF3 has five 'Photo Style' color response presets in addition to its default standard mode. Of interest here is that three of these presets yield different scene brightness at the same camera-reported exposure. 'Scenery' produces a darker image, with middle gray rendered with about 1 EV less luminance. 'Natural' and 'portrait' modes, on the other hand, yield a brighter image 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. In 'scenery' mode, the reduced brightness levels extend from near highlights well through to the midtone region. Imagining its use in a say, a landscape scene, one would expect this mode to allow for more visible detail in brightly lit areas and perhaps greater saturation in lush foliage.
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.