Noisey greens!?

N

n0signal

Active member
Hey all.

I've not long had my DVX100A and have not really had a chance to properly use and test it completely. However, something I only noticed the other day was that for some reason greens seem to be a bit noisey. Well, lets just say that I'm noticing more noise than I've done so far and that greens seem to display this more noticebly than other colours.

The culprit is a green waste paper bin that sits underneath my window and I'm filming it when the sun in going down, with the window open, balanced for the natural sunlight. I will post a screen grab and would appreciate some comments about whether this level of noise is acceptible. Just a further not, I was testing lens flare from my UV filter the other day by shooting sunlight filtering through a mesh grid, trying not to shoot too directly into the sun.. still, could it have damaged the green CCD or something!? *worry*
 
Re: Noisey greens!?

How was the exposure when you took this? Or perhaps the gamma? Were you shooting in default settings or screwing around with the scene files?

Also, you mention the sun is going down? This merely could be feedback to lack of light and having the iris opened up too much for compensation.
 
Re: Noisey greens!?

But opening the iris all the way shouldn't introduce graininess...that should come from an artificially brightened picture, not optically (ie. the use of gain, pushing brightness in post, etc).

???
 
Re: Noisey greens!?

Absolutley correct Mike. My bad; I meant to imply emphasis on the low light conditions which would definately not give feedback if the iris opended up. :P But more so if the iris maybe was stopped down?
 
Re: Noisey greens!?

[quote author=John Hudson link=board=Events;num=1085338718;start=0#2 date=05/23/04 at 13:11:01]How was the exposure when you took this?  Or perhaps the gamma?  Were you shooting in default settings or screwing around with the scene files?[/quote]

This was shot in scene file 6 (cine-gamma, cine-matrix D) and the only setting changed is the chroma level to -4. If I recall correctly, I had the first ND filter on and the iris was probably opened right up to 2.8 (telephoto). Do you think the lighting was causing the problem then? For further info, I did another test on the evil green bin but under my crappy room lights... was much better. ND's off (obviously) and iris opened way up... same settings. Also, I tried changing the detail coring and V detail levels and that seems to help remove noise.

Just curious about what caused it in the first place, doesn't seem like it should be there. :-/
 
Re: Noisey greens!?

Hmm...I wouldn't think that it was anything to do with the lighting...it looks like something digital, inside the camera...to do with the *way* it was captured. If your gain was off and everything set basically to normal, I have no idea what the problem could be.

Maybe post a video clip so we can see how the motion looks..?

This is puzzling...




P.S. John I gotcha...how could I have lost faith, if only for such a small moment ;)
 
Re: Noisey greens!?

If you are shooting in scene file 6 you might try changing the "matrix" setting to "normal" instead of "Cine-like". In my experience I have found the "cine-like" matrix setting to produce far more noise than changing any other setting. From looking at the grab, it seems you were teetering between using the ND filter wide open, or using no ND filter at say f-5.6. It looks slightly underexposed, but if this is a pan, then you can have everything exposed perfectly when moving the camera. Try the matrix thing and see if that cleans it up for you.
 
Re: Noisey greens!?

Thanks for all the tips guys, I've bought some colour and monochrome test cards, so will test the camcorder again tonight under the same conditions. I'll try altering the matrix settings as suggested and tell you if it cleans it up.

I guess the number one thing I was worried about is that I might have fried my CCD's in the sun. Is this possible? I only did a few pans across it, was probably exposed to blinding sunlight for 30 seconds max, and never directly, just skirting around it, testing flare.
 
Re: Noisey greens!?

No no no

Tht wouldnt do it. As a rule I try not to SPOT the sun unless its low on the horizon and for pretty shots. Imnot activily seeking to shoot it though :P

Sun light streaming into the EVF? Now thats a whole nutha nightmare.
 
Re: Noisey greens!?

[quote author=John Hudson link=board=Events;num=1085338718;start=0#10 date=05/24/04 at 12:34:19]No no no

Tht wouldnt do it.  As a rule I try not to SPOT the sun unless its low on the horizon and for pretty shots.  Imnot activily seeking to shoot it though  :P [/quote]

Cheers for the reassurance John! :)

Yeah, I remember reading somewhere that CCD's are quite robust and it's only really if you take long exposures into the sun that you can damage them. also remember reading that it leaves a 'smear', rather than generating unwanted noise, which is my problem.

All evidence points to what you said, low light performance, however it is just strange that greens would suffer the most compared with other colours. As far as I remember, reds tend to bleed with video because they reflect a larger part of the spectrum and blue reflects the least. Is that right!? You'd think that blue would give you the most problems with noise in low light then if that is the case, but it is definitely green colours on my camera!!
 
Re: Noisey greens!?

[quote author=scharky link=board=Events;num=1085338718;start=0#8 date=05/23/04 at 16:55:36]Try the matrix thing and see if that cleans it up for you.[/quote]

I tried fiddling with the colour matrix, doesn't help with the green noise problem. Although, altering the V detail and detail coring does, although of course at the expense of finer detail and resolution. Hmm.

You were right, to expose it like that I've been shooting either with an ND on and the aperture wide open, or ND off and the iris stopped down. Ideally, I'll never really shoot in these kinds of uncontrolled and crappy lighting conditions, but it's just irritating that I can't understand the problem. Why are greens specifically more noisey than the rest of the image? Reds and yellows are perfect, no hint of noise. Slight noise on blue and on greyscale. Loads on greens!? >:(
 
Re: Noisey greens!?

I sure don't know. In the early days of the DVX, people used to complain that the blue channel was excessively noisy in comparison to the other channels(!) What you're showing in the greens doesn't look familiar...
 
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