It is basically a soft Circle Power Window (CPW) with a hard-edged Quad Power Window (QPW) mask. The blur starts at the hard edge and is confined by the CPW. To demonstrate the less-than-obvious versatility of this filter, my source image is a quiet harbor shot that does not need "go faster" streaks. The harbor shot is nice enough, but it lacks a focal point.
I decide to focus the viewers' attention on the boats at the center of the image and make an initial grade, avoiding the cliché vignette on this occasion. To create reflections on the water, I load the motion blur filter using powergrade. This will make the water less murky, and also lead the eye towards the boats. To begin with, I re-position the Power Windows to the center of the screen. The Motion Blur algorithm has controls for horizontal blur ( H Blur ), vertical blur ( V Blur ) and Detail, which defines how much of the original sharp image should be visible through the blurred image. Since the reflections are vertical, I set H Blur to 0, and to maximize the effect I also set Detail to 0. Increasing V Blur creates vertical streaks, but because the water is obscured, the effect seems over the water rather than in it. Increasing Detail reveals the water through the effect until it looks like reflections, while increasing H Blur softens the streaks to finish the effect.
My guest colorist wants to save the effect as a PowerGrade so that it can be reproduced with a mouse click. I open the Power Windows to the full width of the screen, for a more general application and save the Colorist Toolbox settings in PowerGrade.
The wider Power Windows look better than my center-based grade, but the reflection effect now makes the foreground boat in the right hand corner look soft. I put the Defocus Circle Power Window over the boat, make it the Output Key, and use it in the Colorist Toolbox as a mask.
That fixes the soft boat problem, and gives me another idea. I use the Defocus Quad Power Window to slightly defocus the buildings, creating a subtle depth of field effect that focuses even more attention on my subject, the boats.
Finally, just for fun, we try the newly made reflection PowerGrade on another shot. It's a girl with a bike looking out to sea. I used a QPW grad effect to add drama to the sky, but the foreground is rather dull. We load the reflection effect, line up the Power Windows, add a touch of warmth inside the Colorist Toolbox region and the shot comes to life!
Kevin Shaw is a freelance colorist and consultant for film, video and data projects.
First published TV y Video 2003.