Hi Jaime,
Iliah sometimes makes things more complicated than they need to be. His reference to using an ISO higher than base ISO in order to obtain blacks that are completely unplugged is mainly in reference to the Sony A900, for which he and others have determined the "low ISO" is 320 instead of the base ISO. For the D3/D700 you can safely shoot at ISO 200 without danger of "plugged" blacks.
HIs reference to "ISO High" is the ISO beyond which you will get equivalent results by adding exposure compensation in the raw processor. For example, an image shot at ISO 3200 on the D3 will look (essentially) equivalent to one shot at ISO 1600 with +1 exposure compensation added in post processing. Iliah has said in the past that "ISO high" can typically be determined by looking in the EXIF to see the point at which "high gain" amplification is applied. In the D3/D700, "high gain" amplification is applied at any ISO above 800, so using those criteria, ISO 800 would be Iliah's "ISO high." The key to understanding Iliah's point is his statement that he can get better results using "positive compressed (curved) exposure compensation in the raw processor." One of Iliah's preferred raw processors is RPP (Mac only) which has the ability to apply compression to the highlights to produce a film-like "shoulder" to the highlights, which can allow you to "compress" more information into a given gamma 2.2 space (Adobe RGB or sRGB).
Let's say for example that you were shooting a high-contrast scene, and shot at ISO 1600, but accidentally "clipped" the highlights. If Iliah shot the same scene at ISO 800, with the intention of applying positive exposure compensation in post processing, then he will have "saved" highlights you clipped, and can post process the image to display proper midtones and all the highlights (albeit compressed slightly) using the "compressed" option of applying exposure compensation in his raw processor. That is also the reason for his caveat that his exposure strategy also depends on the raw processor he is going to use. You might be able to use a similar strategy with NX2 using highlight recovery or a curves adjustment to "compress" the highlights, or ACR using the "recovery" slider, but not quite as effectively as Iliah does with RPP.
My "exposure strategy" differs slightly. I will typically shoot anywhere between ISO 200 and 1600 on the D3, knowing that I will be able to produce an image that has both acceptable dynamic range and noise characteristics. I favor the lower ISOs as much as possible, but won't hesitate to go up to ISO 1600 if I need that ISO to get a decent shutter speed. You won't loose significant DR until ISOs higher than 1600, and those higher ISOs will show a corresponding increase in noise. However, I find that even ISO 3200 will produce acceptable results for most applications where I need that speed (event photography, etc.). I also try to avoid ISO 2000 and higher because that is where the automatic noise reduction kicks in, which significantly slows down processing on my older PC (due for replacement soon).
Hope this helps,
Keith
