Post Magazine

February 2014

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40 Post • February 2014 O ne of the key aspects of performing color correction well is being able to analyze an image; and one of the most important ways to analyze an image is with a good external waveform monitor or rasterizer. Though many people have access to software-based "internal" waveform monitors in nonlinear editing systems or desktop color correction software, there are a couple of issues with relying on them to do color grading. Here, we will address the five main reasons to use an external waveform monitor. RESOLUTION The software waveform monitors built into desktop editing and color correction applications get the leftovers when it comes to computing power. Apple, Avid and Black- magic's DaVinci are much more concerned with giving customers a great user experience with no lag in response times or processing, so the companies devote most of the com- puting power in the apps to the actual pro- cess of color correction. So, to lower the drain on the rest of the application, the inter- nal software-based waveform monitors are usually only capable of a quarter resolution, at best. Sometimes the waveform monitors in the applications only sample every eighth line of video. However, when color correcting high quality, definition and resolution are required. Especially with small specular highlights, users could easily lose them with the internal wave- form monitors. External waveform monitors have the dedicated resources to bring the necessary resolution to perform superior color correcting. Another important reason for using exter- nal waveform monitors is that your video card will change the signal. You will want to make your color grades after your video card outputs the signal, not before. The video card output is in the format appropriate for the distribution method and the color space of the final screen, in this case, HDTV, which is in an YCbCr format with a Rec. 709 color space. Another critical advantage of using an external waveform monitor is the ability to easily configure settings, allowing the wave- form monitor to illustrate the exact display or combination of displays that a user will want, all at the touch of a button. This flexibility allows users to customize the displays in an infinite number of ways and save the custom- izations to presets that can be recalled very quickly, at any point in time. The flexibility to recall or change presets is important when a user is trying to get through many grades in a day. Not everyone has the time to dedicate to scrolling through various menus on a screen countless times a day. The final primary benefit of using an external waveform monitor comes into play with functionality and flexibility during the color correction process. One of the things users want to do while grading the primaries is add gain or zoom to a par ticular par t of a scope, such as the middle of the vectorscope or the highlights of a waveform. Most soft- ware waveform monitors can't alter gain or zoom to specific par ts of a scope at all. With- out this functionality, the software waveform monitor cannot make fine, detailed correc- tions. With an external waveform monitor, the scope functionality is not only there, but it's easy to access. EXCLUSIVE TECHNOLOGY The last critical element, which is unique to Tektronix waveform monitors, is the family of patented gamut displays that simply aren't available on other internal or external wave- form monitors. One of the most recent Tek- tronix-exclusive innovations is the Luma Qual- ified Vectorscope (LQV) display. Users can find this in the settings for the vectorscope display. LQV allows users to display a specific tonal range in the vectorscope, for example, to see just the highlights or just the shadows. This specialized option makes it much easier to find a good white or black point, or to match what's happening with the high, middle and shadow trackballs with what's happening on the Luma Qualified Vectorscope. Also unique to Tektronix is that its wave- form monitors are gamut displays. The dia- mond and split-diamond displays may look a little foreign, but these are gaining greater acceptance for balancing footage in color cor- rection and camera set-up. These are power- ful displays that are very useful. The basics of the diamond are that the blacks are in the middle of the display, where the diamonds join. Whites are at the other ends of the dia- monds. If the image is balanced, it basically runs right up the middle of the diamonds. When you get the hang of this, balancing is as easy as drawing a straight line. The spearhead display is another gamut display that helps with compliance to broad- cast specs and with creative color correction. The spearhead is a great complement to the vectorscope. Imagine color space described as two cones, brightness to the top of one cone, darkness to the bottom of the other. This is what the HSL color space looks like in three dimensions. So the spearhead and vectorscope com- bined provide a great three-dimensional view of the color space. It's important to view these side by side because a vectorscope doesn't really show saturation in isolation. The excursion of the trace on the vectorscope — how far towards the edge it is — can be driven by saturation, value, or both. The spear- head shows you the difference that the vec- torscope alone can't. These specific functions exemplify the supe- rior ability to execute color correction using an external waveform monitor. Waveform monitors & color correction By RichaRd duvall Technical Marketing Manager, Video Tektronix Beaverton, OR Comparing and contrasting internal and external offerings. Tektronix's WVR 5200 and WFM 5200. External waveform monitors offer the resolution needed for high-end color work. post positions

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