White Balance vs LUT

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James McDonagh

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White Balance vs LUT

PostFri Feb 23, 2018 5:20 pm

Hey guys,

This is a basic cinematography question that I still struggle with no matter how much I look into the technicalities of the issue:

Take this scene from the Godfather for example: clearly this was shot with a white balance which tilted in the direction of orange rather than blue. Could this be achieved with a LUT?

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Dan Sherman

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Re: White Balance vs LUT

PostFri Feb 23, 2018 5:39 pm

James McDonagh wrote:Could this be achieved with a LUT?


Yes, you can find about a million orange & teal luts on the internet.
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James McDonagh

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Re: White Balance vs LUT

PostFri Feb 23, 2018 7:23 pm

Dan Sherman wrote:
James McDonagh wrote:Could this be achieved with a LUT?


Yes, you can find about a million orange & teal luts on the internet.


So are you confirming my suspicion that there is virtually no difference between white balance and LUT?
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Howard Roll

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Re: White Balance vs LUT

PostSat Feb 24, 2018 1:49 am

James McDonagh wrote:Could this be achieved with a LUT?


...or the temp slider.
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Stephen Press

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Re: White Balance vs LUT

PostSat Feb 24, 2018 3:26 am

Before LUT's there were warm cards
Image


The thing is LUTs do more than just colortemp.
"A cameraman with out a camera is just a man"
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Dan Sherman

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Re: White Balance vs LUT

PostSat Feb 24, 2018 4:08 am

James McDonagh wrote:So are you confirming my suspicion that there is virtually no difference between white balance and LUT?


Luts can do a lot more than just shift white balance.
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James McDonagh

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Re: White Balance vs LUT

PostSat Feb 24, 2018 10:33 am

Dan Sherman wrote:
James McDonagh wrote:So are you confirming my suspicion that there is virtually no difference between white balance and LUT?


Luts can do a lot more than just shift white balance.



So in essence what white balance you select is ultimately irrelevant as it can be adjusted in post?
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John Brawley

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Re: White Balance vs LUT

PostSat Feb 24, 2018 3:16 pm

You posted a clip that was shot on film, which works a bit differently to what I’m about to explain here.

The idea of white balance is to “balance” the RGB channels for the sensor in the given lighting conditions.

It’s good practice to start from a neutral place and THEN put your creative look or take on top of that. You could say that all colour correction is usually first balancing shots and THEN creatively grading on top of that.

Otherwise you double up on corrections and you’re fighting the initial sensor response.

Once you start getting big corrections, you may be able to match but the amount you have to move the grade around is inconsistent and it’s harder to match shot to shot. Big corrections can also show up limitations in bit depth and compression sooner as well.

If you start from the same place each time you’ll have a much easier time of applying your creative look.

A LUT also tends to be a downstream correction, whereas a lot of these white point corrections can tend to happen earlier or upstream (depends on RAW or ProRes and application being used)

You may be able to time a shot that was shot 5600k in 3200k lighting but you’ve used up some wriggle room in getting it back to that point.

JB
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Jason R. Johnston

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Re: White Balance vs LUT

PostSat Feb 24, 2018 7:10 pm

Unless you’re shooting in raw, you need to correctly white balance your digital video camera before applying a LUT. You can neutral white balance or you can white balance creatively depending on what you’re trying to achieve emotionally. That’s why they make warm and cool cards. Applying a LUT changes what colors look like since it literally is a look up table tbat describes what color this wavelength captured by the sensor will appear later. Reds can become orange, black becomes blue, despite a neutral color balance. It just depends.

But in the short term, no. Whte balance and LUTs are two competely different things and have nothing to do with each other in operation. They CAN if you plan ahead or shoot with a monitor LUT or something. But you need to get your white balance nailed on the day and apply or create LUTs later. It makes post easier when you plan ahead. Even if you’re shooting raw, white balancing makes shooting less confusing.

John Brawley wrote:You posted a clip that was shot on film, which works a bit differently


I was gonna say that. :D
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timbutt2

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Re: White Balance vs LUT

PostMon Feb 26, 2018 12:05 am

Via the Chinatown (1974) Trivia Page on IMDb:

According to Roman Polanski's autobiography, he was outraged when he got the first batch of dailies back from the lab. Due to the success of The Godfather (1972), Producer Robert Evans had ordered the lab to give this movie a reddish look. Polanski demanded that the film be corrected.

So, the takeaway here is that the warm reddish look can be achieved in post production as much as on set. The key is that shooting correctly balanced footage is always the most important key for having a good starting point. Then you grade from there the desired look.

My suggestion would be to have a good neutral LUT to light the scene and balance the white balance. Then switch over to your "look" LUT that has the Godfather warm feel.

One thing I do is get my camera balanced to the lights that I'm using clean, and then add gels to the lights for the desired lighting colors. That gives a look to the correctly balanced footage in camera via the lighting. And then from there you can take it further in the grade.
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Ric Murray

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Re: White Balance vs LUT

PostMon Feb 26, 2018 6:58 pm

Here's another way to think about it. When shooting any compressed wrapped format (anything other than RAW), the idea is to evenly expose all three channels (RG&B) equally and evenly, using as much of the dynamic range as possible. By adjusting the white balance to the light source you get very close to that goal. If you set camera to indoor (3200K) and shoot outdoors under daylight (5500K) you will be overexposing the B channel and underexposing the R channel. Trying to balance that later with a LUT can be done, but will not look as good because the B channel will likely be clipped in the highlights and the shadows will be noisy in the R channel. You are "baking in" limitations that you will trying to correct "against" later.
Creativity is the ability to accept ambiguity.
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Stu Aitken

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Re: White Balance vs LUT

PostTue Feb 27, 2018 8:36 pm

lots of good points above

some additional blathering if it helps from someone on the post side:

the Godfather was made before the vast array of nuanced colour correction tools we have today were available or achievable (you had limited chemical/lighting based CC that could be done at the film printing stage of course) so a lot of creative choices had to be done in camera as it were (eg exposing indoor tungsten lighting on outdoor daylight film or vice versa, gelling lights, etc) - same with FX, as CG didn't exist back then :)

A LUT is essentially a colour transform that says for a variety of defined points in the colour gamut shift from original value A to new value B. They have limited resolution (ie number of defined points in a 3d matrix that covers R,G and B) so when applying a LUT there will be additional "interpolation" of how values map from A to B on any colour values that fall in between those defined points.

This is a long way of saying a LUT in general is an imperfect tool, though these days they can do a lot, and they can effectively encapsulate most end results of possible colour correction strategies, including making stuff warmer or cooler or otherwise tweaking 'white balance' in post. They are "dumb" however in that the transforms they describe are set in stone pretty much.

as other have pointed out the way a LUT works in practice to achieve a "look" thus relies on the source material (ie what you have shot on file) being consistent in terms of the changes it will make also being consistently predictable. The best way ensure that is to shoot consistently, and then do a prepass colour correction to make it even more consistent before any 'creative look' colour correction (inc via LUTS) are applied on top

OTOH this doesn't stop you also doing things similar to what they did on the Godfather in camera (eg by exposing tungsten at 6000k instead of 3200k say so everything looks 'warm') but on a digital sensor it will work slightly differently from film. If the image is 'baked' (ie you are saving to anything but a raw format) then the camera itself is already doing lots of subtle things to the image based on what it thinks (or rather the engineers who designed it think) is going to create the best image in the given limits of the format its saving to, and the sensor HW itself and those assumptions might not work well with the intended effect. You could say the same thing with film as well I guess - its just with Digital there's way more going on.

White balancing in post (inc using a LUT to do a similar transform) is different from white balancing in-camera because of that 'image baking' that happens in camera, which almost always throws out information in the process for one reason or another (usually to reduce file sizes or computation overhead in the camera) that may have consequences re achieving a look later on (eg a 'successful' white balance change)

interestingly if I look at that godfather clip you linked to I do rather think it feels quite odd colour wise out of context (yes I know its a classic!)- so again - there were analogous issues in film days also but far less room for maneuver as well
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Denny Smith

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Re: White Balance vs LUT

PostWed Feb 28, 2018 3:20 am

Film prints could also be color corrected or the overall look changed by using filters during the printing process also.
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James McDonagh

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Re: White Balance vs LUT

PostThu Mar 01, 2018 12:58 pm

All fantastic answers here, guys. I really appreciate the wisdom being divulged :D

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