Noise Filter?

[Digigenic]

:?:
Have any of you ever heard of a "noise" filter?
I've always known of traditional filters, UV, ND, Polarizers, etc.
But, according to one of my vidy mags, a noise filter is rather common when shooting in low light in order to reduce noise.
It sounds good and all, a real solution, but I've never heard of such a thing until now.
Is it an actual lens filter, or post filter?
Most of the time, I'm using a DV camera rated at 3 lux or better, so low light noise has never been an issue anyway. But, for future reference, I was just curious to know if any of you had ever heard of such a thing? If so, who makes them?

 

[David Mullen ASC]

A noise filter would be a post process, also called noise reduction. Often it involves some sampling of the image from surrounding frames or some softening of the high-frequency detail like is done to remove aliasing problems (sharpening an image in post tends to enhance the noise as well). I'm not sure of the details -- I'm more familiar with grain reduction in post, which is similar. I know that as you crank up some forms of noise reduction like DVNR, you get a motion "lag" or smear due to building up the frame from overlaying the previous frames.

 

[Digigenic]

Thanks,
I'm also looking at the noise reduction settings that can be found within a camera. The XL2 has a couple different settings that are said to facilitate the noise reduction process.

 

[David Mullen ASC]

I'd be curious to know more about how the XL2 does that. Most pro cameras don't have any particular noise reducer other than shooting at minus-db on the gain.

 

[Digigenic]

Well, as far as I know within the XL2's cinematic settings, there are 3 particular variables among 11+ settings that deal with noise reduction.
The first setting is plainly called "Noise Reduction", which is said to remove video noise-non picture artifacts such as those commonly found in low-light images-without hurting image detail or creating motion artifacts.
The second setting for noise reduction is called "Coring", which is said to help decrease image noise by reducing fine detail information that is not a major contributor to the picture detail.
The third setting is simply called "Black", which allows you to control the depth of black, whereby deepening it would likely kill any noise that may be floating about in those areas.
Then, there's another new setting on the power dial specifically for low light shooting. Some of the other settings are for Gamma control, Knee (H/M/L), Color Matrix, Sharpness, Color Phase, Film Grain, and skin detail.

 

[David Mullen ASC]

Sounds like you'd end up with darker and softer shadows as a result -- basically they are reducing the sensitivity and edge-sharpening in the low end areas, and then crushing the blacks to boot.

There's basically no free lunch here.

 

[Digigenic]

Canon's claiming it will retain sharpness and detail, but when I think back to what I was seeing on some of the review monitors at the Expo, the image was a little too soft and blotchy.
That's one of the reasons why the DVX100a is expected to remain a better "out of the box" choice, because they too have similar settings, but when their settings are activated it still retains sharpness and doesn't create a blotchy picture.
We’ll know soon enough, likely sometime this month when a production model is tested against the DVX100a.