JPEG Tone Curves / dynamic range
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.
Note: this page features our new interactive dynamic range comparison widget. The wedges below the graph 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).
At its default Active D-Lighting setting of 'ADL Off', the D7100 exhibits a tone curve that differs somewhat from its predecessor the D7000, by displaying a more gentle roll-off from maximum white to highlight detail. In practice, this means that with the D7100 you can gain about .3EV stop more highlight information while maintaining identical midpoint and shadow renderings. The D7100 also exhibits a less contrasty tone curve than recent Nikon DSLRs like the D5200 and D600. Total JPEG dynamic range on the D7100 is roughly 9.5EV, with about 4.5EV in the highlights, again with a relatively gradual roll-off at the top end. Shooting in Raw mode will of course give you more headroom, allowing you to recover some of the brighter tones that might end up being clipped in the D7100's default JPEG mode.
The D7100 offers six different 'Picture Controls', which are essentially color response presets applied to in-camera JPEGs. They all offer the same highlight range but vary image contrast by adjusting the shadow tones to provide either richer blacks or maintain more shadow detail.
The default mode is 'Standard', which yields just over four stops of highlight range from middle gray to clipped white. The 'Vivid' and 'Landscape' options boost image contrast and give deeper shadows, which results in earlier clipping to black. 'Portrait' mode, on the other hand, protects shadows by maintaining detail at the darker end of the tonal range.
The D7100 offers five discrete settings for Active D-Lighting (ADL) in addition to an 'Auto' option. Nikon's ADL modes seek to retain highlight and shadow detail in high contrast scenes by combining under-exposure (via a shutter speed adjustment) with manipulation of the image's tone curve.
Comparing the effects of ADL at its extremes - Off and Extra High - you can see that in our studio test scene the highlights are extended by almost 1 stop EV, albeit with a very abrupt transition between clipped whites and highlight detail. In ADL 'Normal' mode you can achieve a roughly .3EV gain in highlight information in comparison to shooting with ADL turned off.