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 cameras) black to clipped white (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' 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 the camera can capture before it clips to white. Shadow range is more complicated, in our test we stop measuring values below middle gray 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.
Film Mode setting
The Panasonic GF1 has nine preset film modes, six in color and three black and white. All 'film types' can be modified in terms of contrast, sharpness, saturation and noise reduction and there also two user-definable 'My Film' settings. As you can see from the graph all settings demonstrate subtly different tone curves (as each has a slightly different contrast setting) with the Nostalgic and Vibrant/Dynamic settings marking the extremes. They show considerably lighter and darker mid tones respectively. If you're concerned about highlight range/clipping it's worth noting that there is a whole stop of difference between the most contrasty setting (Vivid, which clips harshly) and the least contrasty (Smooth and Nostalgic) modes.
The GF1 offers five levels of contrast (we've only shown the extremes here), but as you can see the difference between the tone curves applied is minimal (and is mainly concerned with lifting the shadows). There's no real difference in dynamic range (and crucially, no difference at all in highlight range). We're all for offering the ability to make subtle changes to the tone curve, but it would be nice if Panasonic offered more latitude when it comes to changing the contrast - this hardly seems worth the effort.
ISO Sensitivity and Dynamic Range (JPEG)
At its standard settings the DMC-GF1 delivers 8.5 stops of dynamic range at ISO 100, which is slightly higher than the G1 only because noise reduction in the shadows keeps noise above our cut off point (highlight range is essentially the same). With just over 3 stops of highlight range the GF1 is broadly comparable with other Four Thirds and APS-C cameras, though the rather harsh tone curve means it can't quite match the best of its competitors (including the Olympus E-P1, which at ISO 200 gives you almost a third of a stop more). Highlight range falls slightly as you head up the range (though as the figures below show, noise reduction at the default setting is high enough to stretch the shadow range out considerably).
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-5.4 EV||3.1 EV||8.5 EV|
|ISO 200||-5.4 EV||3.1 EV||8.5 EV|
|ISO 400||-5.4 EV||3.0 EV||8.5 EV|
|ISO 800||-6.4 EV||2.9 EV||9.3 EV|
|ISO 1600||-7.7 EV||2.8 EV||10.6 EV|
|ISO 3200||-4.7EV||2.9 EV||7.6 EV|
Dynamic Range compared
Thanks to the rather harsh tone curve the GF1's highlight dynamic range can't match the best mid-range DLSRs, and at 3.1 EV it can't quite compete with the Olympus E-P1 (at ISO 200). The fact that the GF1 tends to meter quite conservatively (i.e. slightly under exposes) - or can be forced to with a -0.3 EV compensation - means that the highlight retention in 'real world' images is as good as - often better than - the E-P1.
|Camera (base ISO)||
|Panasonic GF1||-5.4 EV||3.1 EV||8.5 EV|
|Panasonic G1||-5.0 EV||3.0 EV||8.0 EV|
|Nikon D5000||-4.8 EV||4.0 EV||8.8 EV|
|Canon 500D||-5.1 EV||3.4 EV||8.5 EV|
|Olympus E-620||-5.4 EV||3.9 EV||9.2 EV|
|Olympus E-P1 (ISO 200)||-5.7 EV||3.4 EV||9.1 EV|
The wedges below 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).
Experience has told us that there is typically around 1 EV (one stop) of extra information available at the highlight end in RAW files and that a negative digital exposure compensation when converting such files can recover detail lost to over-exposure. As with previous reviews we settled on Adobe Camera RAW for conversion to retrieve the maximum dynamic range from our test shots.
As you can see the default Adobe Camera RAW conversion delivers less dynamic range than JPEG from the camera (a more contrasty tone curve and less noise reduction in shadows). After experimenting with both ACR and Silkypix we managed to squeeze just shy of 10 stops out of the same file, of which just under 1.0 EV extra was in the highlights (stretching the highlight range to around 4.0 EV), though at that point color was seriously compromised.
|ACR Default||7.4 EV|
|ACR Auto||9.6 EV|
|ACR 'manual'||9.9 EV|
WARNING: Although ACR and Silkypix were able to retrieve the 'luminance' (brightness) of wedge steps which were previously clipped there's no guarantee of color accuracy as individual channels clip before others.
Looking at real world examples it soon becomes clear that the GF1's usable headroom is, as our studio tests suggested, limited to around a stop or so. This means that whilst you can pull back slightly washed out blue skies and correct a modest amount of over exposure, you should most certainly not expect miracles. The first example below shows pretty much the limit of how far you can pull back a raw file before you start to see serious color problems (with magenta creeping into the clipped areas). As with the Olympus E-P1 there's around a stop or so of 100% recoverable highlight detail, though you can normally push it to around -1.5 stops if the shot isn't too over exposed.
|Camera JPEG||Adobe Camera RAW with -1.5 EV digital comp.|
In the following examples we've gone a lot further to see if seriously over exposed shots (as in the first example) or completely washed-out skies (the second example) can be rescued by significantly higher levels of negative digital exposure compensation. As you can clearly see the answer is a resounding no; clipped areas remain clipped, and even when some tone is recovered it has either no color information or a noticeable magenta tint. Anything more than about 1.3 stops risks this magenta tinge (caused by channels clipping at different levels) to creep into the brightest areas.
|Camera JPEG||Adobe Camera RAW with -2.5 EV digital comp.|
|Camera JPEG||Adobe Camera RAW with -2.75 EV digital comp.|