Tutorial: Color Correction with Avid Media Composer

Working in the Hue Offsets Tab

In the HSL tab, the next tab below the Controls tab is the Hue Offsets tab (Figure 14, below). This is the equivalent to FCP 7's three-way color corrector. The three color wheels allow you to control the hue and saturation of your shadows, midtones, and highlights. These are analogous to the three color balls on the manual interface you see many colorists use.

Figure 14. The Hue Offsets tab with its three color wheels. Click the image to see it at full size.

To counteract an improper balance in an image like something mis-white-balanced too blue, move the center crosshairs in the opposite direction. Or to add, for example, some warmth in your midtones, move the center crosshairs on your mid-tones wheel towards red or yellow. Below them are numerical entries for those luma ranges and also an eyedropper that allows you to sample a spot on your image. The eyedropper under the shadow circle allows you to click on a spot that should be black and do an auto black balance. The one under the mids circle allows you to click a spot that should be gray to set a gray balance. And the one under the highlights circle allows you to click on an area that should be white to set a white balance.

To the right are gain, gamut and setup controls. Below those are more controls for doing automatic corrections. The first icon allows you to set an overall auto balance, balancing your colors. The next allows you to set the levels of your blacks to their lowest legal level. And the next allows you to set auto contrast, lowering blacks to their lowest level and highlights to their highest legal level. The final icon allows you to automatically set your highlights to their highest legal level.

All of the controls to the right work the same as the ones that were in the Controls tab. The only difference is that, when you match colors, you can choose to match just your shadows, midtones and highlights, instead of HSL.

The Curves Tab

Finally, in the Curves tab (Figure 15, below), you have four graphs. These represent your color channels, red, green, and blue. And also your master for adjusting luma, gamma, and black levels. At the bottom of the master graph is back and the top is white. For the color graphs, the level of black for each color is at the bottom and the highest amount of that color is at the top.

Figure 15. The Curves tab. Click on the image to see it at full size.

To best understand this, let’s look at an RGB Waveform Monitor for a chip chart (Figure 16, below).

Figure 16. The RGB Waveform Monitor.

The RGB Waveform Monitor shows the amount of red, green, and blue in the image. The trick to understanding and using the RGB Parade is to understand a basic principle of color. A pure black image has equal amounts of red, green and blue, very little of any of them. A pure gray image also has equal amounts of red, green, and blue--about 50 percent of each. And a pure white image also has equal amounts of red, green, and blue, about 100 percent of each. The RGB Waveform Monitor is basically a graph showing the amounts of each color--R, G, and B--in the image. If an image is balanced, the three graphs will look about the same. If the image is unbalanced--say, “mis-white balanced too blue”--then the blue channel will be the strongest.

The curves for each color channel allow you to manipulate the shadows, the bottom of the graph; the midtones, the middle of the graph; and the highlights, the top of the graph. The Master allows you to affect all three channels equally.

Moving the bottom of the red graph will directly manipulate the shadows or bottom of the red level of the RGB Parade. Moving the top of the blue graph will directly manipulate the top of the blue level in the RGB Parade. Manipulating the middle of the master will directly manipulate the middle ranges of all three color channels on the RGB Parade. Experiment with this and you will see this is a very powerful way to do color correction.

Below the graphs are Reset buttons that can be used to toggle the correction in each graph on or off. If you want to reset a graph to a factory default, simply Alt-click (Windows) or Option-click (Mac OS) to reset that graph.

There are also numerical entries under each graph. To the right of the graphs are a Master Saturation Slider and Sliders for Master Gain, Master Gamma, and Master Setup (black). To the right of those controls are the same controls in the other two tabs. There are a few differences though. When matching colors, instead of matching HSL or shadows, midtones, and highlights, here you can match RGB master levels or you can do what Avid calls a natural match, which is usually the best option.

At the bottom of these buttons are three icons for doing automatic color corrections. The first allows you to remove color casts. Click the eyedropper and then click on something that should be white or black in your image. The next icon allows you to auto-balance the entire image. And the third icon applies an auto-contrast move, setting your blacks to their lowest legal level and your whites to their highest legal level.

A Few More Tips on Color Correction in Avid

A few other quick tips about the Color Correction interface is that color grades can be saved in bins. Just drag the rainbow rectangle icon from the Color Correction Interface to a bin. You can name these saved corrections in the bin if you want. You can also map the Save Correction icon to a keyboard command (Figure 17, below). Then when you’re parked on a current correction, just tap the Save Correction button to save the correction to an active bin.

Figure 17. Saving a Correction in the Command Palette. Click the image to see it at full size.

You can also save sampled colors to a bin. Sample a color with either of the two color chips by clicking and dragging from the color chip to the spot on the image you wanna save or sample. Then Option-drag (Mac OS)/Alt-drag (Windows) the sampled color chip to the bin. The chip is automatically named with the HTML color name and the RGB values of the color. But you can rename this something descriptive like “Client Approved Skin Tone.” You can then drag these back from the bin to the right color chip to be able to match another color to it. For example, using this technique a skin tone from one scene can be automatically matched to the skin tone in another scene.

Leaving Color Correction Mode

Leaving Color Correction mode is simple. Switch to Source/Record Editing mode or to your Source/Record Editing workspace or any other workspace. To revise an edit or a color correction, just go back to the other mode. All of your corrections follow you instantly between modes with no need to round trip. You can play and view your corrections without having to render, though rendering before exporting or laying off to tape is a good idea.

I hope this has given you a feeling for the controls and the power of the color correction tools inside of Avid and the reason that the way Avid handles color correction is much easier and more efficient than other NLEs. 

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