Thu 02-Feb-12 10:10 PM | edited Fri 03-Feb-12 01:20 AM by ericbowles
We've had some discussion about the pros and cons of Active D-Lighting in this and other forums. I've done some testing and would like to share some observations - then open it up for discussion.
I Photographed two different high contrast scenes with a D300, Nikon 24-70 lens, and a tripod. I took 36 test images using ISO 200 and 3200, and all settings for ADL - Off, Low, Normal, and High. Picture Control was set on Neutral to apply no enhancements to contrast or sharpening.
Active D-Lighting does two things - it adjusts exposure and then applies an alternative curve to the exposure. For my test images, with ADL turned off, using matrix metering I was getting an exposure of 1/400 sec at f/8 and ISO 200.
With ADL on Low the exposure was the same, but the change in the curve caused slightly brighter shadows.
With ADL on Normal, exposure was reduced by 1/3 stop to 1/500 sec. The change in the curve to the right side of the histogram was more pronounced.
With ADL on High exposure was reduced by 2/3 stop to 1/640 sec. There was a significant brightening of the shadows with a little more noise. The shift of the curve to the right was pronounced.
In each case the shift of the curve to the right includes a small amount of shift in the blacks, and a much larger shift in the white end to nearly completely make up for the slower exposure.
One other factor to keep in mind is the ability to reverse ADL in post processing. If ADL is turned On at any level, Capture NX2 shows an edit step which can be used to turn off ADL or change it to any of the other settings. When you turn off ADL in post processing, any exposure adjustment remains, but the curve is eliminated. That means your image looks 2/3 stop underexposed if you were using ADL High, but with ADL Low only the curve is removed and exposure is still the same as with ADL off.
But even with ADL on Low, the difference in the curve can be significant. In my test images the high and low value were unchanged, but the shape of the histogram changed. The result was that if ADL was turned off in post, the light ares of the image became even brighter but not to the point of blowing any highlights.