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.
Active D-Lighting feature
D-Lighting is a shadow & highlight enhancement feature first seen on Nikon's Coolpix range of compact cameras and later on the D200. When it was first introduced it was an after-the-fact filter which you could apply to images in playback mode. On the latest Nikons 'Active' D-Lighting is a menu setting which is applied to all images (working on the raw data) if enabled. There are four levels (and an auto mode) available; Off, Low, Normal and High. Rather than only adjusting the shape of the tone curve (as most similar systems do) setting higher levels appears to apply a third of a stop negative exposure compensation (typically slightly higher shutter speed).
Below you can see a graphical representation of the curve produced by each setting. Highlight range is being extended by approximately half a stop in the 'High' setting. The shadow range remains largely unaffected. The effect is subtle to say the least, but might come in handy in some situations.
Below you can see how the numerical results that you can see plotted in the graph translate into real life. We exposed both shots to get some detail on the brickwork of the dark tunnel. Naturally this results in an overexposure of the buildings you can see outside. As you can see in the crops Active D-Lighting managed to recover a small amount of highlight detail on the brickwork.
|Active D-Lighting Off, 1/8 sec||Active D-Lighting High, 1/15 sec|