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 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 GH1 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 are 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 settings marking the extremes. They show considerably lighter and darker mid tones respectively. Changing the Film Mode (or contrast) settings makes little difference to highlight range / the 'clip point'.
ISO Sensitivity and Dynamic Range
With its default settings the DMC-GH1 delivers 7.8 stops of dynamic range at ISO 100. Highlight range extends to 3.0 EV but there is hardly any roll-off, which could lead to rather harsh clipping at the extreme highlight end of the scale. Shadow range stretches down to -4.8 EV at ISO 100. At higher sensitivities dynamic range becomes limited by increasing shadow noise. The GH1's dynamic range is remarkably consistent across the ISO range but slightly lower than what've seen on recent entry level DSLRs.
| Sensitivity | Shadow range | Highlight range | Usable range |
|---|---|---|---|
| ISO 100 | -4.8 EV | 3.0 EV | 7.8 EV |
| ISO 200 | -4.7 EV | 3.0 EV | 7.7 EV |
| ISO 400 | -4.7 EV | 3.0 EV | 7.7 EV |
| ISO 800 | -4.5 EV | 3.0 EV | 7.5 EV |
| ISO 1600 | -4.8 EV | 3.1 EV | 7.9 EV |
| ISO 3200 | -4.8 EV | 3.1 EV | 7.9 EV |
Dynamic Range compared
At standard JPEG settings the GH1 delivers less dynamic range than its closest competitors from the DSLR department. The Canon 500D and Nikon D5000 - both cameras with a larger APS-C format sensor - produce approximately 0.5 EV and 1.0 EV respectively more highlight range and have a more gentle roll-off. The other camera in this comparison with a Four Thirds sensor, the Olympus E-620, produces its maximum highlight of 3.9 EV range at ISO 200. At ISO 100 it's much closer to the GH1 which leads us to suspect that Olympus applies a non-deactivateable 'dynamic range enhancement' technology to the E-620 images.
| Camera (ISO 100) | Shadow range |
Highlight range |
Usable range |
|---|---|---|---|
| Panasonic GH1 | -4.8 EV | 3.0 EV | 7.8 EV |
| Canon EOS 500D | -5.1 EV | 3.4 EV | 8.6 EV |
| Nikon D5000 | -4.8 EV | 4.0 EV | 8.8 EV |
| Olympus E-620 | -5.3 EV | 3.9 EV | 9.2 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).
|
RAW headroom
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). The best we could achieve was 10.5 EV of total dynamic range. However, this only includes 0.4 EV of extra highlight range.
- ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Brightness 50
- ACR Best: Exp. -1.0 EV, Blacks 0, Contrast -50, Brightness 68
| Settings | Usable range |
|---|---|
| JPEG | 7.8 EV |
| ACR Default | 7.0 EV |
| ACR 'Best' | 10.5 EV |
WARNING: Although ACR was 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. This can be seen fairly clearly in the examples below. As soon as you apply a small amount of negative exposure compensation (-0.5 EV in this case) the blown out sky turns purple.
In the bottom image even 4 stops negative exposure compensation only reveal marginally more detail in the blown out areas of the image. In terms of RAW headroom there's really not a lot here to work with on the GH1.
| Adobe Camera RAW default conversion | Adobe Camera RAW with -0.5 EV digital comp. |
|---|---|
 |
 |
 |
 |
| Adobe Camera RAW default conversion | Adobe Camera RAW with -4.0 EV digital comp. |
 |
 |
 |
 |
Comments