Dumb histogram question

[John Marchant]

When I'm working in Redcine-X I find I'm always pushing the black point down using the shadow tool, as a typical histogram will start out looking something like this:



If I were to grab a shot with the lens cap on, or in total darkness, I still see the same little ramp up to the extreme left of the histogram as seen above. Since there's no light there at all in that scenario, all that the histogram is showing me is the natural noise floor of the sensor, at least I that's what I assume... Should the camera ever record data that would show up any lower in brightness on the histogram? Am I throwing away detail by pushing that first little 'ramp' off the left of my histogram? It doesn't feel like I am, but I'm aware that my edit suite setup is not as special as some....

Anyone care to share?

[Graeme Nattress]

All image sensors tend to have a black offset in their readouts. Also, the distribution of the read noise - which is what you're seeing in a lens cap shot, means that you'll get an equal amount of noise below nominal black as well as above, in a bell curve distribution.

Now, you could just crush the below black values out of existence, but we preserve them as the full noise-floor characteristic through the compression. It is therefore up to you how you deal with it - leave them as is, crush them with "Shadow" or -ve Lift, or use the curve controls to gently roll them into pure black.

Graeme

[John Marchant]

Thanks for the 'from the horse's mouth' answer Graeme, much appreciated. Glad I've been interpreting this correctly :)

[John Fairstein]

I use curve controls or Shadow to crush the noise floor, otherwise the clip looks milky. Though you can crush on a clip-by-clip basis, does it make sense to apply the crush globally to all the clips in the timeline after you have graded them individually or in groups? The noise floor seems to be constant for all clips. Does applying a global Look overwrite the individual Looks applied to clips?

All image sensors tend to have a black offset in their readouts. Also, the distribution of the read noise - which is what you're seeing in a lens cap shot, means that you'll get an equal amount of noise below nominal black as well as above, in a bell curve distribution.

Now, you could just crush the below black values out of existence, but we preserve them as the full noise-floor characteristic through the compression. It is therefore up to you how you deal with it - leave them as is, crush them with "Shadow" or -ve Lift, or use the curve controls to gently roll them into pure black.

Graeme

[Stephen Lovett]

Hi John,

One approach is to create a look in RedCineX, and then apply that look to the clips you want to crush.

That can be individual clips or the entire time line for example.

There are lots of ways to get there, really depends on your workflow.

Cheers,

Steve