Dark original with noise and color spilling

[Karovaldas]

I have some footage that was shot in a dark hospital ward. It's dark, so there's a lot of noise grain. There's also quite a bit of red and blue color spill (sorry, don't know the technical term for this) on monochrome surfaces--redish and blueish rainbows where they should not be.

How do I clean this up best? I used Convolution3D with settings suggested in the DV to DVD guide and that worked well on the noise. There was no change in the chromatic aberations as far as I can tell, though.

Also, if anyone cares, to the naked eye, it seems like PeachSmoother with its default settings did a better job than Convolution3D and in half the time, mind you. The solid color walls look smoother and the whole picture looks sharper. Convolution3D gave me a look that I would characterize as too hard--noise was reduced dramatically, but it was replaced with unnatural looking patterns of pixels that make the walls look like they were computer generated.

In any case, how do people deal with dark footage? I think that DV cameras are known for their poor picture quality when it comes to dark scenes (at least this was the case back when I was buying my miniDV Panasonic 601) so the darkness should have come to someone's attention.

Thanks.

[mustardman]

I don't know a good answer to your problem, but I too have noticed that DV performs quite badly on dark scenes (at least with a JVC camera - I have yet to try my new Canon!).

Removing noise - I havn't tried peach smoother, never needed to. But I have tried several of the smart temporal smoothers, with quite good results.

Colour bleed - not really the name for it in your case, as entire areas are coloured, it is not because a bright coloured area has "bled" into an adjacent area. I can only suggest doing some processing in the Y-Cr-Cb colourspace (working with the chroma signals). It may be possible to "scale down" the colour when the luminance is below a certain threshold?

I too would like to know how people (in general) deal with dark footage!

[SomeJoe]

Originally posted by Karovaldas
IThere's also quite a bit of red and blue color spill (sorry, don't know the technical term for this) on monochrome surfaces--redish and blueish rainbows where they should not be.


What you're describing doesn't sound like an artifact in the DV data, but a side effect of your TV set.

If you're viewing a picture using a composite (RCA) or RF (coax) connector, the chrominance information is mixed together with the luminance information. The TV set re-separates these signals using a "comb filter".

But comb filters aren't perfect. If the luminance frequencies happen to be in the neighborhood of the chrominance subcarrier frequency, you get these red and blue moire/rainbow patterns, and red/blue fringes on objects. This most often is visible in two situations:

1. Where the camera filmed fine, repeating, high-contrast detail (like tennis racquet strings). The strings may be white, and the background black, but the TV will show this red/blue rainbow on the whole tennis racquet face.

2. Fine white text on a black background. You'll see the edges of the white text colored blue & red. (Note that this is a different cause of red and blue than what results from a convergence problem, typical with projection TVs that have separate red, blue, & green guns).

To eliminate this problem, use an S-Video (NTSC) or SCART (PAL) cable to connect the DV playback device to the TV. The S-Video/SCART cables keep luminance and chrominance signals separate, thus avoiding the red/blue coloring because the signals don't get processed by the comb filter.

Now, if this isn't the problem, then that tells us that the red/blue is actually recorded on the DV tape. You can verify this by using an NLE on your PC to export a frame capture of the DV and see if the red/blue patterns are there. If so, the camera recorded the scene this way, and correcting it would be extremely difficult.

[Karovaldas]

Thanks for the replies and the attention to the problem.

The color problems I am describing are not taking place on the TV screen. I see them on stopped frame on the PC. Using various software players--they are always there... They are also not occurring in any of the circumstances that you are describing (strings, thin lettering). Where I noticed them was on the surgical pants of a nurse. The pants are unicolor blueish green and they have something similar to subtle Northern lights on them in red and blue.

What is NLE? and how do you do it? Is capturing a frame the same thing?

Would it help if I were to capture a frame and post it? I am not sure how to do that either ... I mean how to get an attachment to this forum message. I could forward you an e-mail or something like that...

[SomeJoe]

Originally posted by Karovaldas
What is NLE? and how do you do it? Is capturing a frame the same thing?

NLE = Non-Linear Editor. i.e. a Video editing program, like Adobe Premiere, Vegas Video, etc. They can import and edit DV, apply effect, transitions, titles, etc.

I'm not sure what programs you're using, but most things that can play back DV can save a frame from the video as a .bmp or .jpg. This is the "frame capture" I was talking about.

It indeed might be helpful if you could post a frame that shows the color issue -- placing it on a personal web site and posting the link here is the ideal way.