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I understand (ref) that I can do my own post processing to get the same effect that Active D-Lighting gives.
But does the in-camera ADL get applied to the raw image data or is it only done to the accompanying jpeg (when shooting RAW+JPEG) It might be nice to see the preview image with that effect, knowing that the Raw image is still unmodifed.
If it only affects the jpeg, what does ADL do when shooting RAW only?
No and yes, mostly no though :)
ADL does not affect RAW data directly. However it sometimes affects exposure, which therefore gives you a different RAW file under the same circumstance with ADL turned Off.
Trying this on a Nikon Coolpix A, with ADL off, on a given scene I get 1/320s F/2.8 @ ISO 800 but as I increase a ADL from Low to Extra-High, the shutter-speed goes up incrementally, seemingly by 1/3 stop on each step: 1/400s, 1/500s, 1/640s, 1/800s. This says that ADL is trying to preserve more details in highlights, this always happens at the expense of shadow noise.
However, this depends on the scene and results in a less predictable camera experience. It may give you a better exposure but I strongly suggest you get to know the metering system and use Exposure-Compensation (EC) as needed which puts things in your control.
I have a Nikon D3s, only take raw files from the camera, and keep active D-lighting on most of the time.
The purpose of ADL is to avoid blowing highlights that are too small or off-target to be otherwise metered. This is a common problem with digital cameras, especially point and shoots.
Imagine a scene where most of it is in open shadow, but someone off to the side is wearing a white shirt and sunlight happens to hit the shirt and little else. The metering system will adjust the exposure so that all but the white shirt is exposed reasonably. However, the white shirt will be one saturated blob of white. You won't be able to see any of the folds of the cloth, for example. Such blown highlight areas make a picture look bad and are annoying to look at. It can make observers judge the photograph as "poor", possibly without being aware of why. ADL looks for such highlight areas and turns down the exposure so that they are captured just at the end of the sensor's range.
So why wouldn't you always do that? Because the downside is loss of discrimination in dark areas. With a very high dynamic range scene, you end up choosing between splotching out the light areas or splotching out the dark areas. The reason I leave ADL on most of the time is that splotching out dark areas is usually more acceptable, and the D3s has a amazing sensor with best in class dynamic range. Put another way, with the D3s I usually don't have to choose. I can not splotch the highlights, but still have enough brightness resolution in the dark areas to make a good picture.
You don't want to go too far with this. While you don't want to blow out whole bright areas, it's fine to blow out small reflection from polished metal and the like. Those are many many times brighter than even the medium dark areas of most scenes, and today's sensor simply can't handle that. Fortunately, such blown reflections and the like don't make a picture look bad.
Regardless of all this, you still have to take care in post processing. Only you can decide how bright you need to show detail, after which it's OK to saturate. ADL captures the real data in the extra bright areas so you can make this choice.
ADL doesn't cause any processing to happen to your RAW, but it does affect metering. If you want to replicate the effect then you can set the EC to underexpose.
But rather than just relying on metering and having the camera intentionally underexposure to prevent accidental clipping of highlights, a better approach is to use the histogram to judge the exposure and make adjustments as necessary. Or better still (since there is still no manufacturer that offers RAW histograms) bracket your shots.
when you set your image format to raw, each of them will have a jpeg thumbnail embedded in it. so any setting you use (pic control, adl, etc) is applied to that jpeg. thats how the camera display the picture on the lcd, with all settings applied.
other than that, the exif data will contain the settings too. when you open the raw file with nikon capture nx, the settings will be applied to the raw. then you can adjust the settings again from there if you want.
lightroom and may be other software do not recognize these settings unfortunately.
If you are taking both jpeg and RAW, ADL will certainly give you better jpegs if you have set the ADL correctly. The RAW files are are usually unaffected, but that depends on the camera.
I had a huge problem with active D lighting causing me to wind up with underexposed RAW files.
Basically it was lifting all the shadows in a shot by about 4.5 stops (it was on extra high). That resulted in photos that had the bare minimum exposed in the shadows looking like perfectly exposed images (perfect to edit later). This was more in ambient lit, evening scenes.
When I'd import to my laptop I found the photos were about 4 stops under, and that I had to push the exposure slider that far to get decent shots, which limited my ability to edit freely and also meant I had to make use of tons of noise reduction in Light Room.
I finally figured out what the cause of my problems was and switched ADL off today. So that's a warning to everybody, just know that ADL will cause shadows that have minimal details in a dark environment appear correctly exposed on the back of camera.
