Our new 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.
ISO Sensitivity and Dynamic Range
As expected the D80 delivers a fairly predictable eight stops of dynamic range, and managed to do so right up to the recommended ISO 1600, although interestingly highlight range was very slightly (we're talking tiny amounts here) higher at ISO 200 than at ISO 100 and thanks to noise reduction shadow range sneaks higher at ISO 1600 than at ISO 800 (although there won't be any useful detail).
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-4.8 EV||3.2 EV||8.0 EV|
|ISO 200||-4.7 EV||3.3 EV||8.0 EV|
|ISO 400||-4.6 EV||3.3 EV||7.9 EV|
|ISO 800||-4.5 EV||3.2 EV||7.8 EV|
|ISO 1600||-4.7 EV||3.1 EV||7.8 EV|
|ISO 3200||-3.0 EV||3.1 EV||6.1 EV|
Dynamic Range compared
There's no significant difference here between any of these cameras, other than the EOS 30D's slightly better shadow performance, although it's questionable whether you would ever be able to take full advantage of that. There is a difference in the actual tone curve, with both the Sony and Canon showing a more gradual roll-off in highlights, the D80 a more linear response from middle gray to the clipping point (this is fairly typically Nikon-like).
(Note that we would have liked to include the Canon EOS 400D in this comparison but unfortunately did not have time to complete the tests before publication of this review, we will of course include the D80 in our EOS 400D review).
|Camera (ISO 100)||
|Nikon D80||-4.8 EV||3.2 EV||8.0 EV|
|Sony DSLR-A100||-4.8 EV||3.3 EV||8.1 EV|
|Canon EOS 30D||-5.1 EV||3.3 EV||8.4 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 to the nearest third of a stop (the exact range is calculated to sub-stop fractions and using calibration data).
Next we will test the additional headroom available in RAW files. 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 from the graph and wedges below Adobe Camera RAW in default mode actually returns a little less dynamic range, a combination of a more contrasty tone curve and more noise in shadow areas means it is cut-off by our 'lowest acceptable SNR'. The best we could achieve (with some extreme ACR settings) was a pretty impressive 10.4 stops total dynamic range, most of this is at the shadow end (the highlight range, above middle gray) gains just under one stop.
- ACR Default: Exp. 0.0 EV, Shadows 5, Bright. 50, Contrast 25, Curve Medium (Default)
- ACR Best: Exp. -0.75 EV, Shadows 0, Bright. 50, Contrast -50, Curve Linear
One thing to bear in mind is that 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 may clip before others. (Note that the wedge below labeled as 'ISO 100' is of course a JPEG straight from the camera).