Posted October 06 2011 - 04:43 PM
Good black levels should mean (reasonably) faithful representation of the bottom end of the tonal range. The details should be there as a result, *but* that does *not* necessarily mean they are always easily visible (and easily captured by a still camera and then represented on the web). How easily visible they are depends on the original intended look of the image. Sometimes, the content creator only intends for the dark regions to look like shadows w/ very faint hints of detail, not for the detail w/in to be easily discerned as though they were fairly well lit compared to the rest of the shot, eg. deep shadows of a distant forest in a grand vista shot in bright midday light. Other times, the content creator may intend for the shadows to be the primary focus of the image and thus may design the image to reveal more easily visible details, eg. the area seemingly directly lit by a candle-light source in a candle lit scene, but not necessarily the entire scene in the darker corners of the scene where the light presumably should not reveal much of anything. Of course, the examples I gave are more or less on the opposite extreme ends of the spectrum and there will be a good deal of variations in between, but they serve to illustrate the point.
So in the end, how much can be easily seen *should* really depend on the image and its intended look itself, not merely on our own personal desires to see every little detail that can possible exist in those dark regions. Seeing the image outside of the intended look (whether that yields more visible details in the shadows or not) will essentially mean altering what the content creator had originally intended to show you. And in actual practice, achieving good black levels will probably involve some sort of compromises because of all the real world limitations that exist -- and don't forget that your actual viewing environment will have a lot of impact on what good black levels will mean in actual practice...
BTW, this is precisely why you often see grayscale log step bars presented along w/ whatever very well presented web images that are intended to be seen as faithfully as possible (usually on camera/photography sites w/ the bars displayed perhaps at the bottom of the page or in some separate display calibration page). They are there to help you adjust your web display to more faithfully present the web images they accompany to their fullest tonal range, so the whites, blacks and various ranges of grays can be all seen as faithfully as feasibly possible.
Hope that helps some...
Just another amateur learning to paint w/ "the light of the world".
"Whatever is true, whatever is honorable, whatever is right, whatever is pure, whatever is lovely, whatever is of good repute, if there is any excellence and if anything worthy of praise, dwell on these things..." (St. Paul)