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 D800 exhibits a tone curve that is virtually identical to that of its big brother, the Nikon D4. Both cameras offer more subdued highlights than the 'punchier' rendering of the Canon 5D Mark III. The relatively gentle transition from highlight detail to clipped whites makes for a smooth transition of tones while still maintaining a generally pleasing image contrast (see our real world ADL samples).
The D800 offers six different 'Picture Controls', which are essentially color response presets applied to in-camera JPEGs. While none of these vary global image brightness, they do provide options for slightly adjusting the highlight and/or shadow range of the processed image. See the Features page of this review for a demonstration of these presets on a real-world image.
The default mode is 'Standard', which yields an impressive four stops of dynamic range from middle gray to clipped white. The 'Vivid' and 'Landscape' options boost image contrast by reducing dynamic range, having a more pronounced effect on heavy shadows, which are set closer to maximum black. 'Portrait' mode, on the other hand, protects shadows by maintaining detail at the darker end of the camera's dynamic range, sacrificing perhaps 1/3 stop of highlight range in the process.
The D800 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. The real-world effects of these options can be found on the Features page of our review.
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 as much as 1 stop EV, albeit with a very abrupt transition between clipped whites and highlight detail. Overall scene brightness is reduced by perhaps 1/3 stop EV in 'Normal', 'High' and 'Extra High' ADL modes in order to expand the highlight range.
In the graph above, we compare the D800's base ISO of 100 with its Lo 1 setting of ISO 50 (equivalent). This lower sensitivity setting is essentially ISO 100 with 1 EV additional exposure and a tone curve adjustment to arrive at a final exposure with the correct brightness. The penalty, as you can see above, is a significant decrease in available highlight range. Given this difference, we would advise shooting at or above ISO 100 to maintain maximum dynamic range, using ND filters instead for situations that require a longer exposure.
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