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Battle of the Software NLEs, Part 1: Overlay, Chromakey, and Color Correction
Posted Aug 1, 2005 Print Version     Page 1of 3 next »
  

In this first of four installments of the Battle of the Software NLEs, we'll compare five leading tools--Adobe Premiere Pro, Apple Final Cut Pro, Avid Xpress Pro, Pinnacle Liquid Edition, and Sony Vegas--as they performed in three operations essential to pro video editing: Overlay, Chromaker, and Color Correction.


All video editors have two different types of features: subjective and objective. Subjective features primarily focus on usability, how intuitive an editor is to work with, and how quickly and easily it performs the splits, trims, cuts, pastes, and insert-this-here/delete-that-there actions that makes up most of video editing. Give two reviewers the same program, and their opinions about these subjective features could easily vary by 180 degrees.

Then there are the objective operations, like Color Correction, Chromakey, Speed Change, Image Stabilization, and similar modifications. You can apply them to a clip or clips, assess the result, and reach a somewhat objective opinion. Certainly there is some subjective element to these tasks--such as how well the controls suit your experience level and editing eye--but give two programs to two different reviewers and the results from these tests should prove reasonably similar.

Here we attempt to measure what is measurable, the objective tasks that most video editors perform and how skillfully each NLE carries them out. Consider it a heptathlon comprised of the following events; Chromakey, Color Correction, HDV editing, Slow Motion, Image Stabilization, Slideshow output, and overall Rendering. Our contestants are Adobe Premiere Pro 1.5, Apple Final Cut Pro 5, Avid Xpress Pro HD, Pinnacle Liquid Edition 6.1, and Sony Vegas 6. Since most users of Premiere Pro will also have Adobe After Effects, courtesy of Adobe's aggressive bundle pricing, we also performed chromakey tests with After Effects.

These are all complex subjects (admittedly, some are more complex than others), and to do them justice, a thorough comparison runs much longer than a single article can accommodate. Thus, we have broken down the Battle of the Software NLEs into four segments. In this segment, we'll look at Overlay, Chromakey, and Color Correction. Next month, Part Two will examine HDV performance and workflow, possibly the hottest postproduction issue for videographers today. Part Three will cover Slow Motion and Image Stabilization, and Part Four will look at Slideshow performance and Rendering, and draw conclusions about the cumulative performance of each solution discussed here. (A DVD with files showing the complete results of these tests can be purchased from Doceo Publishing.

Perfecting the Overlay
Video overlay is a technique used to merge two clips into one final video. Typically, one video is shot against a blue or green screen, then superimposed over a background clip. Using software controls, you instruct the editor to eliminate the background color and combine the two clips.

When applying a chromakey effect, you first choose the background color in the overlay clip, typically with an eyedropper or similar tool, and then adjust "similarity" or an analogous control to increase the range of similar colors eliminated. These are the top two Video Effects controls in Figure 1, a screenshot from Premiere Pro 1.5.

Like most other programs, Premiere Pro has other, less well-defined controls like Blend, Threshold, and Cutoff, which fall into the "wiggle it and see if something good happens" category. These vary by program in name and effect.

Finally, virtually all programs have a Smoothing or Softness control that smooths the edge between the subject of the chromakey--me in Figure 1--and the background video, which in this case is some video of a recent trip to Cyprus. This is an essential control that can make or break your chromakey, so find and use it (you can see "Smoothing" set to High in Figure 1).

Another edge-related control typically found on higher-end programs is called Spill Suppression, which hunts out the last vestiges of the chromakey color and turns it to a less visible gray. This proved particularly useful with Final Cut Pro.

In addition to supplying controls for chromakey, programs provide different "views" for perfecting the effect. Some programs, including Sony Vegas and Premiere Pro, offer a Mask view that substitutes a mask for the subject in the chromakey video (Figure 2). Since the goal is for 100% of the subject to be viewable, any residue in the mask, like the gray spots in Figure 2, usually indicates that your similarity settings are too high and are eliminating regions in the chromakey video. These eliminated regions are manifested as a transparency, where the background shows through the subject. If a Mask view is available, check it before finalizing your settings.

In addition to the Mask view and the normal preview in the application window, all the NLEs evaluated here let you preview out through the DV port to an attached NTSC monitor. While convenient, we saw some differences between the NTSC preview and the actual results, particularly with Premiere Pro. As with many of the skills tested here, it's best to test your chromakey settings with short clips to ensure that you are producing the desired result, then apply the settings to the entire project.



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