Olympus E-410 EVOLT Review
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.
The E-410's gradation setting produces images in low or high keys, it does so by both modifying the tone curve as well as the exposure. In the test shots used to produce the graphs below the E-410 under-exposed the 'Low' shot by 0.7 EV and over-exposed the 'High' shot by 0.3 EV. These settings shift the brightness of the image but don't change the overall dynamic range.
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 steps above our cut-off point) but does not extend highlight range which is always clipped around 2.7 EV.
ISO Sensitivity and Dynamic Range
When I first started shooting with the E-410 I suspected its dynamic range was less than we are used to seeing from a DSLR, that proved to be true once I had done the studio dynamic range tests. These show that while shadow range is what we would expect (between 4.5 and 5 stops) highlight range is limited to 2.7 stops (EV). This leads to an overall 'usable dynamic range' of around 7.3 EV.
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-4.6 EV||2.7 EV||7.3 EV|
|ISO 200||-4.6 EV||2.7 EV||7.3 EV|
|ISO 400||-4.6 EV||2.7 EV||7.3 EV|
|ISO 800||-4.3 EV||2.6 EV||6.9 EV|
|ISO 1600||-3.7 EV||2.6 EV||6.3 EV|
Dynamic Range compared
Here you can see more clearly the difference between the E-410 and the Nikon D40X, Canon EOS 400D (Rebel XTi) and Olympus' own E-330. The E-410 has about 0.7 EV less highlight range (the range above middle gray) than the other cameras here.
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 tells 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.
The most we could achieve using Adobe Camera RAW was a total dynamic range of 9.4 EV although the last stop of this appears to have almost no color information.
- ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Curve Medium
- ACR Best: Exp. -1.5 EV, Blacks 0, Contrast -50, Curve Linear
WARNING: 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.
This can be seen fairly clearly in the examples below, on the right the negative digital exposure compensation has revealed more detail on the face of the building and on the white boats but because at least one channel has completely clipped we end up with a magenta cast to those 'recovered' areas.
|ACR default conversion||ACR with -1.5 EV digital exp. comp.|
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