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 that on earlier models was an after-the-fact filter which you could only apply to images in playback mode, but since the D3 and D300 'Active' D-Lighting is a menu setting which is applied to all images if enabled. There are now five levels available; Off, Low, Normal, High and - new on the D3X - Extra High.
Below you can see a graphical representation of the curve produced by each mode. Rather than only adjusting the shape of the tone curve (as most similar systems do) higher levels of ADL apply up to one stop negative exposure compensation (typically higher shutter speed). This preserves some additional detail in the highlights. The shadows are pushed up by adjusting the tone curve. At the new Extra High setting the system delivers just under a stop of extra highlight range but also reduces dynamic range in the shadows very slightly - a trade-off that many users will be more than happy to accept.
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 on the outside. As you can see in the crops Active D-Lighting managed to recover some highlight detail on the brickwork. The new 'Extra High' setting is indeed slightly stronger than 'High', but the effect is still fairly subtle.
|Active D-Lighting Off, 1/8 sec||Active D-Lighting Extra High, 1/15 sec|