Digital Video - February 2008 - (Page 49) at all, a variation thereof. Without the two alternating rows of color bars and the PLUGE (picture line-up generation equipment), which is the three thin black rectangles near the bottom right), the color bars are relatively useless for field monitor calibration. In this case, I have a tape of just SMPTE color bars that I’ve generated from Final Cut Pro. I play this tape in the camera and then calibrate my monitor from that. This is not the optimum method, but as long as you always use the same tape in whichever camera you’re working with that does not generate the SMPTE bars, then you’re working from a baseline standard and you’ll be much better off than if you don’t have any bars at all. Color charts and gray scales are great tools for image control between location and post, but they are not sufficient tools for monitor calibration. Your best tools is the SMPTE color bars. You start the calibration process with your contrast setting. Generally, you’ll want the contrast to be as high as possible before overdriving it. To do this, turn the contrast all the way up and look at the three large squares at the bottom left hand corner of the color bars. The second one in is a large white box. If you’re overdriving your contrast, this box will “dance” a bit, or vibrate, seeming to be animated. Just turn down your contrast until that “animation” stops. Next, we’ll set the chroma and phase color adjustments. You do this by turning on the “blue check” function on your monitor. When a monitor is set to “blue check” or “blue only,” the red and green rasters in the CRT are turned off so that the image is monochromatic blue. When this happens, the top two sets of color bars appear as alternating blue and black (see image on this page, above). When chroma and phase (color and tint in consumer terms) are correctly aligned, the two sets of bars blend into one another with the blues matching. In a perfect situation, these bars blend so well that you cannot discern between the two distinct rows. In NTSC, this rarely happens, but you get it as close as you can. When the colors are improperly calibrated, these rows will appear as very distinct variations of blue. To calibrate the phase and chroma, make adjustments to each while watching the two sets of bars. You’ll need to alternate between chroma and phase to get it as precise as possible, but you’ll see the bars get closer in hue until the blues in the two rows are as close to matching as you can get them. Once you’ve set your contrast, chroma and phase, it’s time to set your brightness. Turn the “blue check” off so you’re seeing full color bars again. Now you’re looking at the PLUGE, which, again, is the three thin, black, rectangular blocks toward the lower right-hand side (as seen at the top of the opposite page). These three blocks represent blacker-than-black (A), black (B) and www.dv.com lighter than black (C). Slowly adjust the brightness until you can barely just see the third block (C). The other two should blend into the surrounding black, so that you are just barely seeing the third block only. Now you’ve properly calibrated your monitor. The phase, chroma, contrast and brightness levels are properly set and you’re ready to rock and roll camera. Ideally, your monitor is set in a location where there is no extraneous light hitting the screen. In many situations, I’ll build a black tent around the monitor to keep all light off of it and duck into the tent to view the monitor. This is the best-case scenario, but it’s not always possible. It’s also important to understand that, in a best-case scenario the monitor shouldn’t be in total blackness. It’s best to either have a soft glow (optimally, 6500ºK) behind the monitor or a little light hitting the front frame of the monitor without hitting the screen. This takes some careful positioning of a small light fixture with barndoors so that the light just skips across the frame of the monitor. The glow behind or the light on the frame is important to give your eye a neutral reference and keep your eye refreshed, especially if you have the monitor in an otherwise pitch-black tent. We don’t always have the option of providing a perfect environment for the monitor, however, so we have to make due with what we can do. Protect the monitor from stray light as much as you can and remember to calibrate it every time you move the monitor to a different location. If the monitor stays in one location all day long, you only need to calibrate it once per day, or once in the morning and once after lunch. If it moves around from set to set and location to location, you need to recalibrate every time you put it in a new space. It’s also important to use a CRT, not an LCD screen. LCD monitors do not yet have the ability to represent contrast and colors the way a CRT does. Worse, most LCDs have a limited proper viewing angle, and if you’re viewing the image slightly high or low or off to the side, you’re not going to be seeing an accurate representation of the image. With a CRT you don’t have that problem. I’ve have seen some extraordinary new high-end LCD monitors, such as the Panasonic BT-LH2600W, that have very good color reproduction, contrast and a large viewing angle but, for critical image analysis, it still cannot outperform a CRT monitor. The professional CRT monitors are not cheap — and can run in the $20,000 to $30,000 range — but you don’t have to go that crazy. You want to find a good balance between quality, size and cost. I purchased a JVC TM-H1750C 17” professional SD NTSC monitor for about $700 and it has served me well from field monitoring through color correction in post. It’s an important investment that, if carefully cared for, will last a long time. DV dv february 2008 49 http://www.dv.com
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