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.
'Optimize Image' presets
As you can see from the graph below the different 'Optimize Image' parameter presets do deliver different dynamic range / tone responses, this is as we would expect as they do obviously also adjust the gamma curve and contrast. The Softer setting delivers quite a bit more shadow detail and a flatter high tones response. None of these settings however change the highlight range (that above middle gray) which was always around 3.3 EV.
In addition to presets you can manually adjust image parameters. Here we have tested the extremes of the contrast setting from -2 to +2. As you can see the -2 setting does indeed deliver quite a bit more shadow range (because it lifts shadows above our cut-off point) but does not extend highlight range.
ISO Sensitivity and Dynamic Range
No complaints here; we were impressed with the D40X's performance and the D60 actually does a little better (probably thanks to the change in noise handling), delivering a good nine stops of dynamic range virtually all the way from ISO 100 to ISO 400. From ISO 800 you lose about a stop of shadow range for every stop you move up the ISO range.
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-5.7 EV||3.3 EV||9.0 EV|
|ISO 200||-5.7 EV||3.2 EV||8.9 EV|
|ISO 400||-5.7 EV||3.2 EV||8.9 EV|
|ISO 800||-4.7 EV||3.3 EV||8.0 EV|
|ISO 1600||-4.0 EV||3.2 EV||7.2 EV|
|ISO 3200||-3.0 EV||3.1 EV||6.1 EV|
Dynamic Range compared
As the graph below shows the D60 gives you a fraction more highlight and a little more shadow range than its predecessor, and overall is a very close match for the EOS 400D. Only the E-410 shows any real difference (Olympus claims the new E-420 addresses this issue, so we'll update this comparison when we get an E-420).
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).