Active D-Lighting (ADL) has been featured on Nikon's DSLRs for some time now, and is designed for use in high-contrast scenes to maintain shadow and highlight detail in a single exposure. The camera does this by purposefully underexposing the image to maintain highlight detail, then using a tone curve to open up the shadows in its JPEG processing. You can also apply D-Lighting after the fact when processing a raw file, either in-camera or in View NX2 (note that it is no longer called 'Active' D-Lighting though, as it obviously can't adjust the exposure after the event).
The more obvious downside of adjusting exposure to protect highlights is that the shadows must then be brightened post-capture (via a localized tone curve adjustment) which can potentially make noise more visible. Like other current-generation DSLRs, though, the D800's noise floor is low enough that there is little discernible penalty in terms of shadow noise. As such we see little reason why you shouldn't keep ADL turned on throughout a day of shooting.
In the samples below (shot on a tripod but on a very windy day!) you can see the effects of four different strengths of ADL, and compare them to the result with the function turned off. The difference is most visible in in the highlights, which gain additional detail as the ADL setting is increased. An additional mode, 'Auto' applies what the camera considers is an appropriate level of tonal adjustment depending on the scene. All images were shot at ISO 100.
1/200sec. @ f/10
1/250sec. @ f/10
1/200sec. @ f/10
1/320sec. @ f/10
|ADL Extra High
1/400sec. @ f/10
HDR modeThe D800 offers a multiple exposure HDR mode to create images with a dynamic range that exceeds what is possible to capture in a single exposure. With HDR enabled, a press of the shutter generates two separate image captures, each at a different exposure. These are then merged into a single file that combines the highlights from the 'underexposed' image with the shadows from the 'overexposed' image. Because two separate exposures are taken, you will see 'ghosting' alongside objects that are in motion.
There is a delay of several seconds after pressing the shutter while the camera processes the HDR file. Thankfully, when setting the camera to HDR mode you have the option to configure it as a 'one-shot' option. Doing so means that after a single instance of HDR mode, the camera reverts back to normal shooting mode.
While there are obvious benefits to using HDR with a tripod, the D800 does an admirable job of aligning handheld shots, with a composite image that look pleasing even at a 100% screen view. Fast shutter speeds that minimize camera movement deliver the best results. In instances where there is noticeable camera movement, the result is two offset images placed atop one another.
While an 'Auto' option is available, we've had more consistent success by manually selecting the EV difference (either 1, 2 or 3EV) between the two exposures. You can compare their results in the samples below; increasing the HDR amount progressively deepens the blue of the sky, but at the expense of visible haloing around the trees.
|HDR Off||HDR 1EV|
|HDR 2EV||HDR 3EV|
One thing to be aware of is that selecting HDR mode automatically enables the D800's Auto Distortion Control, even if you have this feature explicitly set to 'off' in the menu. This automated lens correction is often accompanied by a slight cropping of the image edges. You can see the effect of both the lens correction and the cropping when comparing the 'HDR Off' image above with any of the HDR-enabled shots.