Nikon D5100 Dynamic Range (JPEG)
Our 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 camera's clipped white point down to black (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' (defined as 50% luminance) 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 above middle gray the camera can capture before it clips to white. Shadow range is more complicated; in our test the line on the graph stops 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 D5100 produces a tone curve that is very similar to what we've seen on previous low-end Nikon models. At standard settings it measures a total dynamic range of approximately 9 EV which compares well to its direct competitors. The measured dynamic range remains unchanged along the ISO scale.
All the different picture control settings offer the same highlight range of approximately 3.5 EV but vary in contrast. The Neutral setting applies the least contrasty tone curve while the vivid and landscape settings produce a 'punchier' tonality.
Active D-Lighting is Nikon's method for capturing more information in the brightest parts of the scene and conveying a wider range of tones in the final image. When the system is activated the camera uses a darker exposure to capture more highlight tones and then analyses the scene and selectively brightens parts of the image to give correct brightness without losing local contrast. ADL offers five settings - Low, Normal, High, Extra High and Auto - or can be totally switched off.
Because the noise floor of the D5100's sensor is so far below the point from which the JPEG's darkest tones are taken, there is essentially no noise penalty to pulling additional detail out of the shadow regions.