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Color correction theory?

Rob B

Rob B

I'm a painter, and have worked in post effects for years, but I amazed that I never really realized how much color correcting thought went into film..

I am currently correcting to my taste.. Basically, free eyeing to a warm or cool lumanistic feel, depending on how the scene lends itself. That said, there must be some rules of thumb I am just mowing over, haha..
 
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I was under the impression that color correction and color grading were 2 different things.

I thought color correction was about making sure that your white is white. For instance if you do a wedding event, your costumers will probably not be very happy if the bride's dress appears yellowish in your footage.

I thought color grading was about making your movie have a specific look. For instance if you do want a yellowish look (like "The Social Network") you would grade accordingly.

But in the tutorial posted by CamVader's the guy goes straight to grading and calls that "correction". So, maybe I'm wrong.
 
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Theo, you're absolutely right. Color correction (as in fixing incorrect white balance) is just so easy to do with modern NLE's that it's not much of a task anymore and, like 2001 said, the terms have blurred together. The guy in the tutorial even worked at ILM, so even the big guys are making the mistake.
 
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Correcting in post for an off-balance image never looks as good as a properly balanced camera original, IMO. If you're going to grade from there, starting with good is always better than starting with lousy.
 
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Funny, I just Skyped with a buddy/DP up in San Jose about this very thing. He corrected me when I used the term Color Correction and meant Color Grading. Good to know that there is a difference!
 
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Theodebernacius said:
I'm starting to wonder if white balance correction is useful at all since after grading white will probably not remain white.
Click to expand...

If you've graded to the point where white isn't white (or appropriate white - think of a white t-shirt at sunset) or skin tones aren't somewhat accurate it's not going to be a look that will be appealing, IMO.

Proper white balance from the camera is important because any grading preset that you've come up with will look different otherwise. White balance correction is a fix for something done incorrectly that can save the day, but at a cost (additional processing and a look that may not be entirely natural).
 
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I suck at color grading/color correction. It's a huge weakness for me.

I just don't have the eye for it. I wish more people understood and had a talent for it in my neighborhood. That would help a lot.
 
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Then, there's something called gamma correction. I don't know exactly what it does. I think it can make dark areas look brighter. But then areas that were already bright just blow out and become white.
 
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To color balance: set your white point with the eyedropper tool in your 3-way color corrector to a known white point (use a clapper board at the beginning of every shot in your production with the white and black bars on top). Then set the black point to the black part of the reference.... make sure you find a frame for this step where the reference is lit by your key light only so that any on set filtration you're doing stays the same (unless you're coloring the key for effect).

Then adjust the levels so your videoscopes (you're using your scopes... right?) hit your pure white points at 100% and not over -- and your blacks at 0% and not under.

Crop your frame to just the actor's face: adjust your mids (gamma) to place that portion at 85% for lighter skin, 65% for darker skin and use the vector scope to place the colors of the mids onto the "Flesh Line." Then undo the crop. Your picture will be BALANCED at that point, mathematically, not by eye.

From there, push it, pull it, wreck it, return it... whatever, but you'll be able to take the grade and move it from shot to shot and know it'll work every single time as the first step makes the shots match, even if they're shot on different days and with slightly different exposures or whatever. The flesh tones will be starting healthy looking and give a good, clean palette upon which to paint.
 
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Gamma correction (and correct me if I'm wrong) creates a film-like luminance curve in the images. While digital cameras record darker and lighter points in an image linearly, film tends to record a wider range of luminances as darker or lighter in what's known as a gamma curve.

In practice, this means that the darker points stay darker, and the brighter points stay brighter. Expensive digital cinema cameras do this automatically.

Hmmm. I hope that makes sense. Here's the wikipedia, which is also damned technical: http://en.wikipedia.org/wiki/Gamma_correction
 
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For all intents and purposes, gamma is simply the relationship of a 50% gray pixel to the output brightness of the same pixel. If you darken the gamma, that 50% pixel will be displayed (arbitrary example number comes next) as 40% which compresses the colors below that value to the 0-40% and stretch the ones above it from 41-100%.

This is how the "curve" is altered to give a more film like exposure.
 
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