Need help with the white balance

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Plecto

Member
Hi. There is just something I just cant understand. Different kind of light sources have different white balances so if I want the camera to pick up the correct colours, I'd have to use the right white balance settings. Some complain about the usage of indoors lightning because of the orange colour of the light, but doesnt just changing the white balance on the camera solve the problem?

And what about lightning filters? Ive heard that fluorescent tubes delivers a very bad lighting with a low white balance. Is putting a CTB filter infront of it solving this problem? And what difference is it between putting CT filters infront of the lamps and putting it infront of the camera? And why is colouring the light while shooting give a better result than editing the colours in post?
 
Your camera and your eyes all attempt to interpret light as being white versus orange or blue or green ,etc The purpose of white balancing is to tell your camera that this particular type of light source should be interpreted as white. Now what happens when you have more than one type of light source in the room ? Well you have to convert all the light sources to being one color temp. For instance let's say you have regular tungsten lights on in a house and you also have daylight coming in from the window. You now have to different color temp. The blueish color from the window and the orangish color from the indoor lights. Since your camera can only recognize one source at a time you can either. Set the white balance for the window and gel the indoor lights or set the white balance for the indoor lights and gel the window.
 
Yes. Just changing the white balance on the camera will solve the problem. If you are shooting indoors with indoor lights then your lights will be giving off a warm light or around 3200 degrees K. "Setting" the white balance simply means "Hey camera, this white card should appear perfectly white in this light". The key is that all the lights in the shot or used to light the shot are balanced with each other (they are all tungsten or 3200K) then all of your colors will accurately reproduce in camera.

Flourescents don't neccesarily have 'bad' lighting. I don't know what a "Low" white balance is but typical household flourecents have a green spike in them, so applying a "minus green" gel gets rid of that. You would put a CTB on a tungsten light that you want to match daylight. If you put a filter in front of the camera everything is tinted that color. In front of the lights then just that area is affected.

Because! You will have more original information and original always looks better. When you adjust stuff in post - especially with DV 4:1:1 color space - then every tiny adjustment you make in post essentially throws away color and resolution information and lets the computer come up with the rest. Did you write the algorithm to do this? No, i didn't think so. After a little while of doing this your pictuure starts to look like crap.
Hollywood can get away with correcting in post because 35mm film does not have any color compression and it is equivalent to a 4K image (twice or 4 times that of HD). The HVX can get away with it somewhat becuase it's HD for one, and the color space is 4:2:2 and it is encoded in RGB. Just more information is what I'm saying. bla, bla, bla...
 
Thanks for replys :D

If I'm filming a scary scene at night and I want everything to have a blue twist, how do you suggest that I do this? By putting several CTB filters infront of the light sources, putting it infront of the camera or poiting the camera at a orange surface and saying that this is white (that would make everything blue, right?)
 
There are a few ways to pull off the moonlight look. CTB gels are one way. Full CTB will absorb 2 stops of light, so that'll require larger fixtures.

You can put a Full CTO gel on the light, white balance off of a white card in front of that light, then remove the gel. You'll get a blue look without losing the light intensity, but that will introduce some grain to your picture. It's a trade off.
 
May I ask why this will cause grain?

What about putting the gel infront of the camera or buying a CTB lens (if this is sold)?
 
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Yeah, you can get a #80 72mm cooling filter for your lens, but you'll still lose light because of it.
 
Yea, but if you have a 500W halogen lamp, putting a CTB gel infront of it would lower the brightness in the same degree as if the CTB gel was put infront of the camera?

I still don't understand why setting the white balance to something that isnt white, would cause grain. Wouldn't this happen nomather what you do (The white balance allways have to be set, right?)? Or is it so that setting the white balance to one sertain value of Kelvin (maybe a value that is shown as real white in the whitebalance scales?) makes the less grain and that the bluer or oranger the light is, away from this sertain value, the more grain the picture will have? If I have gotten this one right, I think Im making progress :D
 
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Setting the white balance causes the camera to shift the red, green, and blue channels, essential adding gain to a channel if necessary to equalize the colors. If there isn't a lot of blue light in the room and you white balance, the camera will have to radically gain up the blue channel to get it to match, and that channel will have lots of grain as a result.
 
Plecto said:
So filming in or setting the camera to about 5500K (pure white) would give the best result?
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The presets are 3.2k and 5.6k.

Daylight is just plain better light. It contains a fuller spectrum of light and more of a blue component. If you shoot outdoors or indoors with daylight-balanced lights your video will look very clean and crisp.

That's not always possible, and good tungsten lights are still good. They will always require the blue channel to be amplified in relation to the other channels. If you are going to shoot under tungsten lights, just make sure that you light well, so there is plenty of light.
 
This may be a little off topic, but Ive heard and experienced that there will be grain on the picture if it is to little light. Do changing the brightness of the image with the iris, ND filter, shutterspeed and 50i/25p cause grain?
 
Plecto said:
This may be a little off topic, but Ive heard and experienced that there will be grain on the picture if it is to little light. Do changing the brightness of the image with the iris, ND filter, shutterspeed and 50i/25p cause grain?
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There is always some noise involved in the image processing. Even under great outdoor lighting, there is very slight noise is the picture. Particularly the DVX is known for having more noise than some other cameras, but many have commented that the noise on the DVX is familiar to the quality of film grain and is quite pleasing.

Normal noise is different than the grain you will get if you use the gain setting on the camera. Then you will start to see real noise. Always avoid gain. Use lighting and exposure so that you do not need gain.

Absolutely, you need to use the ND filters, iris, zebras, and marker features to set the right exposure. An external production monitor and scopes helps as well, but you can get by with what the camera offers.

You can reduce the shutter speed below 1/50 to 1/25 and that will double the light accumulating on the CCD. However a slow shutter like 1/25 will cause significant blurring and is not normal at all. Stick to 1/50 for most normal situations.
 
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