Suggestions for Reducing Blue Noise?

[petereit]

I'm experiencing a funky issue and I hope that some of you video gurus can help.

Check out the first few seconds of the video below. Notice the funky blue swatch across the face of the guy in the background:

http://vimeo.com/6459472

Is this the typical "blue noise under tungsten" issue?

Here are some facts to consider:

I'm shooting under tungsten lighting
Lighting is poor - the camera's iris wide open
Our backdrop is lit by blue LEDs everywhere

If that's the diagnosis, what's the cure? We know we have lighting issues -- it's our next project. Is it as simple as bumping up the lighting so I can stop down the lens? Gels on the lights? Filter on the lens?

As always, any input is appreciated!

[silvaam45]

IAt first I thought it was a chroma key. What are you using for compression?

[camtech]

I've seen this all over, usually with LED blues and purples. Even in some professional productions! I do not believe it has anything to do with tungsten, purely the LEDs.

My (inexperienced) first guess is that the LEDs produce light that is out of range of most camera's image sensors, particularly in the blues.

But a more official synopsis, and a way to fix this (aside from changing LED colors) would be much appreciated!

[zactommo]

I'd also say its most likely an LED issue, but I don't have a technical explaination at the moment for it.

Any chances of trying to replicat the fault? If you could, first thing i'd start messing with is shutter speed, but it looks more to me like a result of too much blue. What caused it to occur in that area, and that time still has me puzzled a bit.

[waynehoskins]

Looks like reflection to me. Perhaps a Nyquist response to a UV component? Perhaps moisture is a contributing factor? (but that wouldn't explain his suit doing it too).

[daver2]

I have seen (what I think) is a similar response at the other end of the spectrum on a monochrome camera to infra red light from a hand-held TV remote control. The camera element is sensitive to infra red radiation but the response is seen by the human in the visible spectrum. It's a great way to see if your infra red remote control is working! This could be the ultra violet equivalent on a colour camera possibly - although what the exact mechanism is I don't know.

Dave

[stevelam]

I have seen a similar thing from flourescent lighting (ie brightline) in studios. They generally take it out somewhere in the studio equipment but I am unsure how they do it? Anybody know?

[tdangelo]

You have not mentioned what type of camera/recording system you are using but I have seen this before with EX1/EX3 recordings where (like yours) the background is oversaturated.

Compare a still from your video to the Mariah Carey (blue color fringing on red hat) still below:

Interestingly enough the previous instances (eg: Mariah Carey) that I have seen were all shaded by the same video guy. Also, in the case of the Mariah shot there were 5600k moving lights creating the hot blue backlight.

Here is what we found out in the shop afterward was causing the problem in the shader's set-up:

Multi Matrix Gate
The Multi Matrix Gate function is added to PAINT 3/6. (See
Figure 10.)
Figure 10
The function confirms which hue is currently selected from the
16-axis color correction function. The selected hue portion is
indicated by the zebra signal in the same way as Skin Gate.
When Matrix Gate is set to ON, the gate signal of the phase that
is selected as PIX is superimposed. When Panel Active is set to
ON, Matrix Gate is turned ON. When Panel Active is set to OFF,
Matrix Gate cannot be turned ON or OFF.

[tomtv]

believe it or not i have seen things like this happen on the sony gear as well. in an emergency we used a spare almost transparent blue gel and re wb and ended up looking fine. but that was eng work and you have to think on your feet sometimes.

[petereit]

Wow, it's been a while since I posted the original message. Turned out to be a perfect storm of too-low lighting, blue LED back lighting and too-high color saturation in the camera.

Upgraded lighting and new JVC GY-HD250U cameras (properly color-calibrated) solved the problem.

Mark

[stevelam]

Awesome! Glad to hear that it's working well. How do you like those 250s?

[petereit]

Competent machines. Wish they were better in low light, but since my pastor moves around quite a bit, the quicker response of the CCDs works out better (no jello). New camera volunteers seem to pick them up pretty quickly, so that's a big plus.