Grain under blue light

M

moonrunner

New member
I recently shot a live concert where considerable blue light was used on the stage.
The camera was set at 24pa, the gain was at 0, shutter was 48, and the iris was at 2.4.

The footage looked nice until the lights turned blue... things got very grainey!

Is this a dirty head issue, a lens issue, settings problem, just the way the DVX100a performs under blue light... or anything else?...

Thanks for any input anyone can give.
 
i get the same thing with blue light. Not sure why exactly, but perhaps its a difficult colour for the camera to discern. But honestly i havent a single clue. Its not grain though its artifact.
 
The Explanation:

The Explanation:

moonrunner said:
I recently shot a live concert where considerable blue light was used on the stage.
The camera was set at 24pa, the gain was at 0, shutter was 48, and the iris was at 2.4.

The footage looked nice until the lights turned blue... things got very grainey!

Is this a dirty head issue, a lens issue, settings problem, just the way the DVX100a performs under blue light... or anything else?...

Thanks for any input anyone can give.
Click to expand...

I am guessing that you were shooting in AWB (automatic white balance) mode.

This all has to do with how the electronic white balancing works. Each channel of the CCD has a different but fixed response to light. When you point the camera at a white card or an 18% grey card and do a custom white balance, you are telling the camera that what ever light you are seeing right now is "white". The camera electronics reads the values coming off the CCD and then applies a correction factor to balance the output of all three channels (RGB) so that it records a white value. The problem is that the farther away from actual white light you go, the more correction factor gets applied to certain channels, in this case, the red and green channels. Electrically this is called amplification. The problem with this is that when your light is mostly blue, there is hardly any red or green signal available, the lower the signal the higher the noise - remember that your electronic noise on these chips is mostly a fixed value. Lower light means that you get closer to the noise floor and you are amplifying noise.

So, even though you have a bright blue light, there is a dire shortage of red and green - those channels amplify what they can to try to give a white balance and you get nasty blotchy noise.

Best regards,
ScreechingHalt Productions
 
Uhh, there's nothing wrong with your camera or your operation of it. Anytime I throw a blue gel on a light, my DVX100 looks NOISY AS HELL! Blue light is a hue that makes the camera look very, very noisy.
 
Well, the blue channel on video is often more noisy than the others. This is partially a limitation of the DV codec, not just the camera itself, although it is common to experience noise with the DVX under blue lighting conditions.
 
A solid wash of blue light is really a worst-case scenario for DV, because blue is the noisiest of the color channels, and your overall image resolution will go soft too (because color resolution is lowest when dealing with primarily colors like red and blue).

DV cameras are not a good choice for shooting blue-lit or red-lit footage.
 
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