Capture NX2 gives you many options in sharpening your images, and defaults to sharpening Luminance as the standard method rather than RGB. This would be like sharpening in LAB in old versions of Photoshop or selecting Luminance sharpening in newer versions.While there are valid numbers that you can set for capture sharpening, the final sharpening of an image depends on how it will be viewed as printed images can be sharpened more than those you post to the web. So there is no one size fits all solution, as it depends on the image. So you essentially use your eyeballs while viewing the image at 100% and sharpen until you just see a halo start to form and back off. You also need to remember that the subject is an issue as well. for example no female model wants you to sharpen her face so that all the flaws show. The best book that covers sharpening is Dan Margolis book Photoshop Professional. Don't let the Photoshop title fool you as the discussion is good for any edit tool that does sharpening.