Posted 29 January 2008 - 01:32 AM
Posted 29 January 2008 - 02:11 AM
You get milky blacks when you try to bring up underexposed images. But when you your scene is purposely underexposed (black), for instance you let the dark areas go under 4 stops do those blacks become blacks or milky?
Think of it this way -- you can't get much blacker than shooting with the lens cap on, or essentially developing unexposed film, right? No exposure, no silver developed, no density (or very little other than base fog level), basically a clear negative once processed.
So you take that clear piece of negative film and you print it at different sets of printer lights, in the 10's, 20's, 30's, 40's. What do you notice? That the blacks in the print are denser when printed at the higher set of printer light numbers, and milky when printed at the low set of printer light numbers.
So it doesn't matter so much how dark the blacks are in the shot, what matters is how you want the overall piece of film printed (or transferred), and usually that is based on how bright overall you want the lit areas to look.
So if you have a face in a piece of light that is one-stop underexposed, surrounded by pure black (several stops underexposed) and you decide that the piece of light shouldn't look one-stop underexposed, it should look a little brighter, then you end up lifting the blacks along with the subject. And conversely, suppose you exposed the lit area normally, but decided to bring it down one stop in brightness -- well, then the blacks will get "crushed", pushed down, printed down, and get denser.
This is why rating the stock a little slower than normal is good because you make sure that you'll be slightly darkening it down to "normal" in post rather than lightening it up to normal.
Now in video transfers, you do have the ability to always set the black areas at "0" essentially, pure video black in digital terms, while adjusting the brightness of the subject, basically messing around with the gamma. But you could get other artifacts than milkiness from too much underexposure, like noise, grain, or unnaturally crushed-looking blacks lacking natural detail.