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White Balance in Digital Cinematography


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This is sort of a mixed question. Long story short I've just bought a sigma fp as my first "cinema Camera". I'm in the process of growing to the next stage as a filmaker. One thing I've always wondered is what are the methods of white balanceing in digital cinematography. I've always liked the look of tungsten balanced film stock so in the past i would just set my camcorder and iphone to 3200k for mostly everything. When digital cameras change color temp is actually changing the way the image interprits light or is it just an affect of in camera post processing. If so wouldn't it just make more sense to this in post. What is the correct methods people use to set white balance on a proffesional setting, both in camera and in post production 

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The individual levels of the red, green, and blue channels after deBayering the sensor's raw signal is what determines color temperature. If you record raw video, then color temperature set on the camera is just stored as metadata to be applied to any conversion to RGB (like the live conversion done so you can see an image in the camera's viewfinder.) In post, the color temperature setting is applied during debayering to RGB.

But if you record any sort of in-camera conversion to RGB, whether in log gamma or Rec.709 gamma (display contrast and color), then the color temperature is baked into the recording so it would involve additional post color-correction to change things.  The more you bake in color and contrast closer to a display image, the better it is to get it right in camera because you have less information in post to work with.  

As for whether to set the camera to 3200K and use an 85 filter in daylight, I don't recommend it -- a camera sensor has a native balance closer to daylight (it is less sensitive to blue wavelengths so prefers an image with more blue). So when you set the camera to 3200K, it is basically pushing the blue channel to compensate for underexposure in that color, making that channel noisier. You don't have much choice in 3200K lighting (other than to use a blue filter on the camera but then you have to use a lot more light) but there is no advantage to leaving the camera at 3200K in daylight (unless you want a blue image in daylight, and even then, a blue filter would be better.)

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Cant speak for all.. but personally  I leave the camera at 5,600K .. unless its very obviously not that .. ie a candle lit room in the night .... even then I would dial it in rather than WB off a card ..  many camera,s have tint now too.. magenta /green .. as long as you have a decent monitor with you .. 

You definitely don't have to do a WB for every shot you do.. the colorist will not like it .. you can only really do it in post if you shoot raw.. 

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17 hours ago, Max Moosbrugger said:

Thanks David. This has given me a lot to think about. Would setting the camera to daylight give me the most information to work with then 

No. If you’ve lit to set to 3200K and you want neutral whites, then you have to correct at some point. If you record raw, it doesn’t matter because white balance is not baked in, but there’s no reason not to set the camera to 3200K so your image on set looks correct. And if you record log or Rec.709, then the color temperature is baked in and you’ll have to boost the blue channel at some point to correct for 3200K, and your recording will be lacking in blue information, so better to let the camera correct for 3200K and then record it rather than record a very warm image and have to fix that later — it’s less of a problem if you record, let’s say, ARRI Log-C 4444 on an Alexa versus bake in Rec.709 gamma, but I’d still get the recorded image close to correct. The only way to get more blue channel information in 3200K lighting would be to use an 80 blue filter and then set the camera to 5600K, but that would mean a 2-stop light loss and 4X the amount of light on set, so it’s not worth it.

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Okay so I'm wondering how do i record a color temp preset versus white balancing each shot. I've been recording all my most recent stuff in cinema DNG Raw, will that mean that any white balance i set is simply meta data that can be changed in post or will i need to simply apply presets via an external monitor. By the way thanks for being so helpful, sorry about all these questions, i just wanna make sure I'm doing it the right way

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I might white-balance once at the start when filming under something like a ceiling of Cool White fluorescents, if I can't get something from using color temp and a magenta/green shift setting, but the point of shooting a scene is to be consistent, even if consistent in an off-color cast. Otherwise you'll be spending a lot of time in post trying to make each shot match each other.

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  • 2 weeks later...
On 6/13/2020 at 3:54 PM, Stewart McLain said:

Would this be your approach even when not shooting raw?  If so, can you please explain the reasons?  Thanks!    

Also, you might not want a neutral look. White balancing a camera brings the whites to neutral. But you might want the scene to play a little warmer or colder than neutral - so you use a preset to dial in the look you like or leave the camera set and adjust the lighting.

Sure you can also make those changes in post - but recording in a "look"  means the rushes are going to look how you want them throughout the edit. Rather than recording everything neutral and hoping the colourist will grade to match your intentions. 

I shot a short years ago using daylight lamps and a 3200k white balance - so it was intentionally very "blue" - sure we could have done that in post - but sometimes there is some merit to committing to a look. (had we shot more neutral, I suspect we'd have chickened out in colour correction and not gone as far) This was in DV days where do didn't have as much latitude in post, you had to basically nail the look in camera. 

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