Comparing Auto Color and Auto Levels in After Effects
Auto Color vs. Auto Levels
Auto Color, Auto Contrast, and Auto Levels have similar names and similar parameters, but they work differently underneath the hood. This means which one you use changes depending on what you trying to achieve and what footage you're trying to use it on. In this movie, we'll compare Auto Levels with Auto Color to color correct a shot and in the next movie, we'll compare Auto Contrast to Auto Levels to help improve the lighting in a scene. The first piece of footage we're going to work with is this outdoor scene of a birdbath. You notice there is water and the white rock.
It has a little bit of a blue cast. This is from reflecting the blue sky. What we want to do is play around with removing this blue cast. Now, whenever we work with Color Correction Effects, it's a really good idea to apply Effect > Color Corrections > Levels and to look at the Histogram to have a better understanding of exactly what it is we are doing to an image. This is the overall luminance distribution of this image. It's pretty even. This is what the Red channel looks like, mostly in the shadows and lower midtones, not much in the highlights. The Green channel, a little bit more information from the plants material that's around the birdbath.
And the Blue channel, and you'll notice that the Blue is indeed very strong through the upper midtones and highlights. This is what's giving us the blue cast in this image. Let's leave this open and see how the histogram changes as we apply different effects. First let's try Effect > Color Correction > Auto Color. Auto Color is a very good effect for removing color cast from an image and returning to a more neutral balance. I'll drag it up before Levels, so I can see the effects on the histogram. This is before and after.
And you can see it's really scaling down the Blue channel, as we look at the image. It is indeed removing a lot of the blue cast from the image. If you want to go further towards a more neutral image, I often check the Snap Neutral Midtones options in Auto Color to again, further neutralize the image. Before and after. That's a much more natural color distribution. Let's look at that Red channel in particular. There is the Red after, before, and you see a bit of movement, a bit of brightening in the Red channel, a little bit of going on in the shadows.
So it is indeed affecting the color channels in this image. And there are other parameters inside Auto Color. Aside from the typical Blend With Original, which you often see, there is a Black Clip and a White Clip parameter. Quite often when you capture footage, there is a bit of gunk around the edges. It may be a black border on the sides, a bit of a white highlight where it clipped out. This is basically saying whether or not you want to ignore some of the blackest and whitest information and not let that throw off the evaluation rest of the image.
The default of looking one-tenth of 1% of the pixels in the image and throwing them out to get a more accurate color representation, this is pretty good place to start. Another thing that's very interesting is Temporal Smoothing. It's number of seconds. When Temporal Smoothing is set to 0, it means that Auto Color or any of these Auto Effects is looking the image every frame in isolation and correcting each frame as it sees fit. However, it can also result in some flickering, particularly if you have something temporarily going through the image.
For example, if there is a bird or an insect flying past here, it may temporarily darken or brighten the image throwing off my Auto Color correction. And so it happens that the image does have a subtle problems as well. I'm going to RAM preview it. Whenever the birds are bathing and causing all these ripples, less of the blue sky is visible in the water and as result there is a different Color Balance during those moments. Watch what's happening with this rock down in this lower left corner. Indeed as the birds start disturbing the water and removing the blue in the water, you'll see that the Auto Color is changing the color of this rock, as it compensates for this.
So this is the case, where we may want to increase Temporal Smoothing to two or say even something like five seconds to average out more frames and not have Auto Color make a correction every single frame. In other words, don't get disturbed by these minor fleeting changes in the footage and just come up with a good average color correction for the entire shot. Now, that's what Auto Color looks like. Auto Levels does something slightly different. As we've seen that Auto Color is scaling the individual color channels, you see how much it's reduced the Blue channel.
It's also reduced the Green channel a little bit, while spreading out the Red channel. Auto Levels instead tries to maximize each of the Red, Green and Blue channels. So I'll apply Color Correction > Auto Levels, and there is actually very little change in this scene because it's already pretty well maxed out in terms of its range. It's before Auto Levels and after. If anything, let's add a little bit more contrast, dip down the midtones. We'll look at the Red channel, Green channel, and Blue channel after Auto Levels.
In this case what Auto Levels is doing is detecting a lack of darks in these individual channels. Like down here in the Blues, and saying let's stretch out our contrast to go ahead and maximize the darks, as well as the brights in each individual color channel. Little bit of movement in the Greens as well. In the Red channel, it already was fairly biased towards the low-end, but again, it's maximizing that low information. Black Clip and White Clip exist in this effect as well.
In this case, where there is not a lot of gunk around the edge of this frame, I might even put Black Clip all the way down to say 0, so as not to crush out my blacks quite as much in this image. Auto Levels has Temporal Smoothing, just as Auto Color did and you'll notice that if we increase Temporal Smoothing to something above 0, that we do indeed get an extra optional Scene Detect button that asks Auto Levels, well, if you do see a certain hard cut in the image, go ahead and change immediately when you detect all the pixels changing at once. Otherwise, smooth out the image and give me an average value when you make your corrections.
Auto Color is good at images that already have pretty full contrast and you need to change the Color Balance. Auto Levels is actually stronger at images that don't have good contrast. They are lacking something in the darks or in the brights. So let's go and look at another scene.
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