Noisy Blacks

[Michael Ludlow]

I have a question about lighting darker areas in a scene. In class I've been hearing you need to light your blacks or your dark areas and I understand this. But what if you want something to be totally black? I thought noise arises when you try to brighten up dark footage. But if you have a scene where one part is at key in frame but another is a EU on your meter or more then 5 stops under and thats what you want, will you find noise in the image? (Film)


Does this apply to digital? I hear the red camera can be noisy in the blacks and in most situations you would light certain areas to a level. Though if your putting someone in shilloute or want a part of a frame to be totally black can you just leave it unlit?

Thanks

 

[David Mullen ASC]

It's something of an old wive's tale that you need to add light/exposure into the blacks to make them blacker and less noisy/grainy. What you need is more overall exposure -- base density, signal strength, whatever -- so you don't have to lift or boost the signal, but instead, bring it down. This in turn lowers the noise.

The only reason you may want to add more light into the shadows is just that by bringing the image down in brightness, either overall or just in the shadows, you may get an increase in contrast as your shadows and blacks become "crushed", so to compensate, you may want more detail in the shadows by adding more light there.

But if you want a pure black area in the frame, like a black background, then just leave it black, no signal in that area at all -- what matters then is how much exposure your midtones and highlights get so you have a strong signal, dense negative, whatever, and can bring down the image in post slightly and thus clean-up the noise.

 

[David Mullen ASC]

In film terms, the blackest area in the frame is the least dense (clearest) area on the negative. Basically a lack of exposure. So you can't really get any blacker than no exposure at all -- just leave the lens cap on or send an unexposed roll to the lab and have it processed. Basically the only density on the developed negative will be the base fog level, a tiny bit of dark haze on the clear negative.

Now take that blank negative and make a print of it. Print it at different printer lights, in the 10's, 20's, 30's, 40's up to 50 (the top limit). What do you notice in the print when you project it? That the solid black image is denser, blacker, at the higher printer light numbers until the print stock reaches D-Max (maximum density.) After that, the blacks can't be any blacker (unless you leave the silver in the print.)

So what does that tell you? That an image that prints at higher printer light numbers will have deeper blacks.

It will also appear to have less overall grain, because if you rate the negative slower, you are exposing the smaller, slower grains between the larger, faster grains, thus "tightening" the grain structure visible in midtones. But in terms of true graininess, i.e. how big the biggest grains are, that's determined by the speed of the stock. Slow films have smaller grains overall than faster films.