Magic Bullet Parametric Curve
Conventional color curve tools let you drag points along an x/y graph to create spline lines, but Parametric Curve lets you create up to five points and then manipulate them with Bezier controls for incredible convenience and output control.
This one-sentence summary fails to do more than superficial justice to Parametric Curve's power, so let's take a quick overview of what Parametric Curve is and the exceptional utility it can offer.
For many years, curves have been a critical tool in brightness, contrast, tone, and color control. For example, if you lower the white output on your red channel, the result will be that your image skews toward cyan.
In After Effects, you can perform these simple curve operations on each color channel and even on alpha. However, After Effects uses a single keyframe to animate dozens of controls underpinning all curve changes. While this all-at-once approach is convenient, it greatly limits precision.
Parametric Curve puts that precision back in users’ hands. Now, red, green, blue, and alpha channel curves each have numerically addressable point controls, all of which can be keyframed separately.
Consider the following image, in which we begin with a default Parametric Curve graph (left). We want to constrain our red channel S-curve by placing the first and third control points at the x/y: 25% and x/y: 75% marks in our graph. Similarly, we want to place the tangent controls for these points on the center line. As with conventional curve tools, we drag the points and eyeball our best placement to obtain the right image.
While our point placements may appear accurate, the truth is Point 1 is not at the 25% mark. Rather, Parametric Curve reveals that it is at x: 25.27 and y: 24.73. Point 5 is similarly inaccurate, and its tangent line is at 90.6°, not a perfect 90 degrees. Numeric controls in Parametric Curve make obtaining our desired values a snap.
Having up to five Bezier points in Parametric Curve solves the perennial problem of curves bulging and twisting in unwanted ways. And what about the usual limitations of not being able to accommodate high-dynamic-range (HDR) values because points and curves are limited by the graph’s edges? As you can see below, Parametric Curve handles off-box points just fine, opening all kinds of creative HDR opportunities.
With one click, Parametric Curve will generate the inverse of your present curve. You might draw a curve to encompass HDR values, then get its exact inversion to pull the image back to standard dynamic range (SDR) values. This is an easy, powerful remedy for highlight clipping. Curve inversion also opens the door to performing color correction between the two curves.
In short, Parametric Curve brings greater control and precision to a range of functions — everything from contrast curves to color correction to using inverse curves for targeting adjustments to achieving the perfect sprite glow in a particle system. And all of that can be done one channel at a time.