NX2 / Exposure Settings

I was reading the following article here in PhotoNet. maybe it can help you:
(link)

Adjusting the "exposure" in any RAW processor, be it NX2, ACR or whatever, simply recovers some of the safety margin that's built into the exposure system of the camera. Since any overexposure of the camera sensor results in unrecoverably blown highlights (i.e. with RGB channel values above 255), the exposure and jpeg conversion of most decent cameras leaves a little headroom in hand. The exposure setting in RAW conversion makes use of these spare levels to bring back some highlight detail, compared to the jpeg version. This usually amounts to the equivalent of between 1 to 1.5 stops exposure, depending on the camera model.

This is obviously not a real adjustment of exposure, since the amount of light that fell on the sensor at the time the picture was taken can't be changed. All that happens is that the margin-for-error allowance is used up, and you can only pull the exposure a small amount before you reach a hard limit where the recovered highlights simply become posterised and turn grey or more usually take on a red or pink cast.

All the above should really be taken as a reason for not using Jpegs, rather than a plus point for the RAW format.

HDR is really a separate issue. IMHO specialist HDR techniques involving multiple exposures are overkill for most of the wide brightness range situations commonly encountered. If you work at 16 bit in RAW and/or Photoshop, there's a lot you can do simply by familiarising yourself with the curves tool. You can also create two "exposures" from a single RAW file and combine them using a suitable blend mode in PS. In most cases the result will be almost indistinguishable from a multi-exposure HDR combo, but a lot will depend on the basic dynamic range of your camera. Modern 14 bit full-frame cameras like the Nikon D700 can have their Raw files pushed by about 4 stops without revealing too much shadow noise, and this gives a useable dynamic range of about 12 stops available for the above pseudo-HDR technique.

Addendum to the above. I can see no technical reason to use more than 2 exposures for any sensible HDR combination. One exposure to capture the highlights without blowing and another to get the required shadow detail. What happens in between can be accommodated using a suitable tone curve adjustment between the two layers and the way in which they're blended.

Two in-camera exposures could easily cover a 20 stop (1 million : 1) subject brightness range, and since the flare factor of most camera body and lens combinations is far greater than .0001 percent it would be hard to imagine a real life situation where this wouldn't suffice. Besides, the above exposure range would mean changing the shutter speed between 1/8000th of a second and two minutes! Enough to rule out all but the most static of subjects, meanwhile keeping your fingers crossed that the lighting doesn't change too much between exposures.

The main difference between bracketing in camera and using EV compensation in NX2 is that if the information is not in the RAW file, there is nothing that any software can do to retrieve it. If the values are outside of the dynamic range of the sensor at the time of exposure, there is nothing that can be done to fix it. If the shadows are too dark for any definition in the RAW file or the highlights are blown, no amount of manipulation in post processing can bring back any detail. So, the advantage of HDR is that there will be definition in all areas on at least one of the exposures (theoretically).

Personally, I have yet to come across a scene where HDR would have been much of an advantage over using color correction points with NX2, and I'm using a D50 with less dynamic range than most newer cameras. I'll post a before and after composite of a shot that I took yesterday. It was manipulated with a total of 2 correction points (one for the metal and one for the sky) and took all of about 30 seconds to do.