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Problem with white balancing


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#1 John1

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Posted 17 July 2014 - 02:33 PM

There is this problem I have with white balance each time I am using white light..... I set my white balance to between 5000 and 5300. Most time 5200 as that is the known color temperature of white light but when I get to the editin room and transfer the video to my system, I end up getting this blueish image. Green appear as blue, blue appear as green signigying there is a problem with my white balancing. But each time I use orange light(red head), I dnt usually av this problem at all. I set my white balance to 3200K for orange light as that is the known color temperature of orange light and my image is always ok. But when I try to save power and use fluorescent light or any white light, I white balnce at between 5000K to 5300K, most times, 5200 but my image end up greenish or blueish. What am I doing wrongly...
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#2 Matthew Padraic Barr

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Posted 17 July 2014 - 10:08 PM

You seem to be misunderstanding the science of light and how it relates to white balancing on video systems. First off, I dont know where you heard that 5300 kelvin is a white light, but the color temperature of daylight ranges quite a bit -- though 5600 is generally referenced as a good number. When you set a white balance, you are essentially telling the camera what kelvin temperature will appear white: setting the white balance with a tungsten light on a white card will set the white balance to around 3200 kelvin -- depending on the exact color temp. of the light -- and everything shot with that same light will appear white, as well as the opposite effect for the higher color temp. which will appear blue. For instance, if you set your white balance to 3200 -- or set the white card with the Tungsten light -- all the daylight in the frame will appear quite blue, which is what you were seeing. For an opposite effect, doing a white balance to a white card in daylight will tell the camera sensor that the daylight should appear white, and thus all the 3200 kelvin, tungsten light will appear warm -- and amber/orange tint.
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#3 John E Clark

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Posted 18 July 2014 - 02:13 AM

There is this problem I have with white balance each time I am using white light..... I set my white balance to between 5000 and 5300. Most time 5200 as that is the known color temperature of white light but when I get to the editin room and transfer the video to my system, I end up getting this blueish image. Green appear as blue, blue appear as green signigying there is a problem with my white balancing. But each time I use orange light(red head), I dnt usually av this problem at all. I set my white balance to 3200K for orange light as that is the known color temperature of orange light and my image is always ok. But when I try to save power and use fluorescent light or any white light, I white balnce at between 5000K to 5300K, most times, 5200 but my image end up greenish or blueish. What am I doing wrongly...

 

When you 'manually' set the Color Temperature to X Kelvin, there is the assumption that the light is 'tungsten/sun like'. that is has a continuous spectrum from deep reds to near ultraviolet.

 

Flourescent lights do not have a continuous spectrum and may have 'spikes' or even 'holes' in the spectrum. This may affect the resulting color rendition that the camera records given the sensor's sensitivities to R,G,B.

 

Most cameras have the ability to 'white balance' from a target of known 'equal' reflectivities for 'white/grey'. On the other hand using a 'tinted' target can introduce certain casts to the resulting image rather than using an optical filter, or post processing twiddling of color controls.

 

Human vision somewhat quickly adapts to the ambient color cast, and so, while one may notice the redishness of tungsten when coming in from daylight, within a few minutes 'white' looks 'white'...


Edited by jeclark2006, 18 July 2014 - 02:15 AM.

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#4 Matthew Padraic Barr

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Posted 18 July 2014 - 06:05 PM

When you 'manually' set the Color Temperature to X Kelvin, there is the assumption that the light is 'tungsten/sun like'. that is has a continuous spectrum from deep reds to near ultraviolet.
 
Flourescent lights do not have a continuous spectrum and may have 'spikes' or even 'holes' in the spectrum. This may affect the resulting color rendition that the camera records given the sensor's sensitivities to R,G,B.
 
Most cameras have the ability to 'white balance' from a target of known 'equal' reflectivities for 'white/grey'. On the other hand using a 'tinted' target can introduce certain casts to the resulting image rather than using an optical filter, or post processing twiddling of color controls.
 
Human vision somewhat quickly adapts to the ambient color cast, and so, while one may notice the redishness of tungsten when coming in from daylight, within a few minutes 'white' looks 'white'...


well said man.
I was a little too brief probably.
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#5 John1

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Posted 24 July 2014 - 06:32 AM

So whats the solution


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#6 John E Clark

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Posted 24 July 2014 - 12:46 PM

So whats the solution

 

Well... there is no one solution...

 

For fluorescent lighting I'd use white balancing from a 'white' target, which should adjust to the actual light falling on the target.

 

One assumption in all this is the light type is not 'mixed'. If one has a mix of tungsten, daylight, fluorescents, then the only thing one can do is filter lights to a common, or as close as possible, color temperature.

 

On the other hand there may be 'story' reasons to not correct the color temperature, but to give the scene some sort of color cast.

 

For example, a parking lot at night. These days usually illuminated with Sodium vapor lights, which, depending may have a single or a very narrow spectrum of light, centering on 'yellow/orange'. But the existing light is not enough to get a good exposure, so, perhaps one uses tungsten lights to improve the illumination levels.

 

In order to maintain that 'parking lot look', using tungsten lights, one would have to filter the tungsten to a more 'yellow' color temperature to maintain the illusion.

 

This takes some experimentation.


Edited by jeclark2006, 24 July 2014 - 12:47 PM.

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