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Color correction methodologies

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There a lot of threads about color correcting, so hopefully it is ok that I start a new one. 😉 The purpose of this thread is to discuss color correction techniques that can be used by the average person. I feel like I am getting better at doing my own color correction, but I am still a complete novice.

One simple method that I like to use is looking at the individual levels of R, G and B. If they are not crushed at either the low or high end, then in Photoshop or After Effects, you can drag the left and right slider to where the slope just starts going up on each end for each color channel. After doing this, the color looks pretty close to correct most of the time especially in outdoor scenes. Whites are white, etc. However, if any of the channels are crushed, then for those channels, you need to adjust the middle slider to eyeball it and usually you need to do this for the other channels as well. After getting the individual color sliders where they need to be, I then go to the combined RGB sliders and adjust the middle one to get the gamma where I want it. Overall, this method works for me most of the time and it is sort of an automatic color adjustment method without needing to know what color each thing in the scene is supposed to be. If it is too red then I adjust the red channel gamma, etc.

Are there any other methods that you use with tools like Photoshop or After Effects to correct the color sort of automatically (without using the Auto-color tool)?

Also, how about in general where, for example, you want the sky to look a perfect blue, but not affect the ground too much without setting up masks to adjust just the sky? Or, the perfect skin color, etc? Do you use the white balance tools in Photoshop to correct the whole frame based on known white, black and gray points?

Thanks,
Mike

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Using levels in Photoshop can be effective, but if you move the left or right hand sliders you’re almost guaranteed to lose information. The reason is that even if you don’t see any detail in the highlights it’s still likely that there is some detail there. A much safer way of changing the highlights and shadows is to use an RGB curves adjustment. After shifting the overall curve, you can go into the individual color curves to fine-tune the adjustment.

If you’re using Photoshop, I’ve occasionally found the Color Balance tool to be helpful.

As for getting a particular gradient to a certain hue, the Channel Mixer is a powerful tool. Since the primary color of skin is red, you can adjust the hue of the skin tones by adding/subtracting green and blue to/from the red channel. Green carries much more luminosity information than blue or red, so if you add green to the red channel you’ll get brighter skin tones. It takes practice, and isn’t appropriate for all situations, but it’s very useful.

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Thanks. I never know how to adjust the curves. Is there a method that can be used where you can just look at the R, G, and B curves and align them similar to my method with the left and right side of the levels without needing to look at what it is doing to the color and it gets it pretty close to correct? I hope that makes sense… I find it difficult to just blindly make adjustments because what I think looks good might not be correct at all. With my above method, it takes all of the colors into account and aligns them pretty well and things look correct. It also spreads the color out across the full range which boosts the saturation, for better or for worse. I would prefer to use a method that doesn’t lose any information as you mentioned, but I am looking for something to help me do it correctly even if I was color blind.

I will start playing with the Channel Mixer as well. Thanks for the tips!

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Here’s what I came up with:

http://www.framecompare.com/image-compare/screenshotcomparison/7Y7NNN8X

Keep in mind I have no idea how this shot is supposed to look, but if you’re just going for a neutral color scheme, find areas that are supposed to be white, gray, and black, and correct them to be neutral. The black dress, the gray crosses, and the white side of the church are good points to keep in mind.

The first version has a reddish cast and a greenish sky, and is the most out-of-balance to me. The second one is better, but it still has a slight reddish cast to the ground and sky. What I did was use a curves adjustment in Photoshop, bringing up the brightness and lowering the red slightly. And that’s it, really.

DuracellEnergizer: "^He’s embraced the absurd. Don’t expect to gain any conventional understanding from his posts."
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Thanks! Here are the two screenshots using the levels adjustment method from my first post. There is some “junk” at the left side of the levels that I removed to get the left and right side aligned between the R, G, and B channels. I didn’t use anything in the picture to come up with the color correction. I just looked at the histogram and slid the left and right sides to just before the ramp ups. I also added adjusting the gamma to show the darker areas are in tact. I over adjusted it, but it can be done less so to bring up the dark areas just a bit.

http://www.framecompare.com/image-compare/screenshotcomparison/7YWNNN8X

I will see if I can get similar results by playing around with the curves and other tools you mentioned when I have some more free time. Thanks again!

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Here is the “final” version using my method and not making it so tight. It still corrects the color, but doesn’t clip as much.
http://www.framecompare.com/image-compare/screenshotcomparison/7YGNNN8X

And here is the same but further adjusted using the channel mixer to try to get the sky to be less green in the Bluray1 version: http://www.framecompare.com/image-compare/screenshotcomparison/91MNNN8U

Edit: I just started playing with the Curves option and noticed I can use my same method because there are sliders, but there is a “show clipping” checkbox. This is really cool because I can adjust to the edge of the ramp up just before clipping and it still works sort of automatically. After doing the curves, I can go into levels and adjust the middle slider to get the gamma without clipping and then use the channel mixer to make subtle tweaks from there. Very cool!

Edit 2: just for fun I tried Auto Color and it ended up looking almost identical to the method I mentioned in my first Edit. The problem with Auto Color is it can’t be reliably applied the same way to each frame in a sequence of frames from the same scene.

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Good work.

One thing to keep in mind with the Channel Mixer - the values for each channel must equal 100, or the color will either clip or be too low. Therefore, if you want to add blue for example, the Curves Adjustment is the best way to do that.

DuracellEnergizer: "^He’s embraced the absurd. Don’t expect to gain any conventional understanding from his posts."
A New Hope Technicolor Recreation (Released!)
The Force Awakens Restructured (V2 Released!) and Starlight Project

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Should not this thread be moved to “How-To’s and Technical Discussions”?

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