Color Correction Basics – Working with the Waveform

Most color grading workflows include two types of tasks: color correction and look design. Look design is what you do to give your story its individual character: it’s the visual style that communicates mood and place.

For example an action film might have a gritty, de-saturated look; a horror story might have a cold blue otherworldly look, a period piece might have vibrant colors, like a painting or an old color photograph. Different scenes within a film usually use slightly different palettes. In short, look design is a part of storytelling Look design is a very exciting aspect of the new digital filmmaking tools: we never had as much freedom as we do now to define how we want our productions to look.

Before you get to detailed look design, you will usually want to begin by color correcting your shots.

Color correction is about balancing your black and white levels, making different shots match each other, and perhaps doing a little sweeting to make sure your shots look good.

Welcome to the Waveform
Choose the clip you want to work on and position the playhead at a good representative frame from this shot.

If you need refreshers, check our blog posts on locating and loading footage in SpeedGrade.

The first step in color correction is balancing your blacks. You can do it visually, but it is much faster and much accurate to use the Waveform display (you can also use the Histogram, but I find the Waveform simpler).

Click the waveform button or press W on your keyboard to activate the waveform display. It appears on the right side of your image by default, but you can click the little arrow at the top of the display (beside the lock) to move it over to the left side. You can also drag the edge of the Waveform display to make it wider (and a little easier to read).

The SpeedGrade CS6 Waveform display is a great tool for helping you balance your colors quickly and easily.

The SpeedGrade CS6 Waveform display is a great tool for helping you balance your colors quickly and easily.

The Waveform display shows the pixel densities for the Red, Green, and Blue channels in your image. The image above shows all three channels floating somewhere between 20 (in the shadows) and 70 (in the highlights). To get the shot balanced, we’ll want the shadows to come down to around 0 and the highlights to reach up towards 90.

What is the Waveform telling us? Any parts of the image that go below 0 or above 100 are outside the visible spectrum. We call that “clipping,” or “crushing the blacks” and “blowing out the highlights.”

Because the Lumetri Deep Color Engine works non-destructively, you can’t lose image detail while working in SpeedGrade, but if you rendered out content with clipping in it, the detail in those areas would be gone. For stylistic reasons, that may be acceptable, but usually those decisions are made later, as part of your look design: color correction is about getting your shots to look their best.

Balancing the Blacks
With the image in your monitor and the Waveform turned on, right click on the Offset color wheel to activate the Virtual Trackball. In Virtual Trackball mode, scrolling actions turn the outside dial (luminance, or brightness) on the color wheel. Mouse or trackpad movements adjust the crosshairs (chrominance, or color).

Dial the luminance clockwise or (more likely) counter-clockwise to pull the RGB channels down towards the zero point. Stop when you get there and click on the color wheel to de-activate the Virtual Trackball.

Dial your blacks down until the RGB channels reach the zero point.

Dial your blacks down until the RGB channels reach the zero point.

I can’t see what your images looks like, but usually when you make this simple adjustment, you’ll notice the contrast is improved and the colors start to pop more.

Balancing the Whites
Continuing on with the same image, now right-click on the Gain color wheel. With that awesome Virtual Trackball activated, scroll to dial the luminance up or down until to tips of the reach up around 90 on the Waveform.

After you have balanced your blacks, the next step in color correction is to balance the whites in your image.

After you have balanced your blacks, the next step in color correction is to balance the whites in your image.

Balancing the Colors
SpeedGrade CS6 has two really useful sliders for Temperature and Magenta and you can use these to quickly pull up one of the Red, Green, or Blue channels so that they are nicely balanced.

These basic balancing adjustments quickly get your images looking great.

These basic balancing adjustments quickly get your images looking great.

From Shot to Shot
With these simple adjustments, you can move pretty quickly from shot to shot to get the balance for each one right. Just move the playhead from clip to clip and make them look great!

We’ll continue with more color correction and look design tips in our upcoming blog posts.

Meanwhile:
Check out Colin Smith’s popular walk-through of SpeedGrade CS6.
Buy SpeedGrade right now! (Or download the free SpeedGrade CS6 30-day trial)
For help, or any technical questions, visit the SpeedGrade user forums.

3 Responses to Color Correction Basics – Working with the Waveform

  1. David says:

    Hi Eric,

    Thanks for these tips, it’s helpful to revisit these basics.

    Any chance you could share with us about how to match shots using a Macbeth color chart?

    Many Thanks,

    David

  2. Pingback: The Basics of Working With Waveforms | CineTechnica