How to Read a Waveform for Video
Before the rise of the chaos of digital video, analog video was ruled by engineers at virtually every stride of production, mail production, and delivery. In that location were rules that had to exist adhered to very strictly to ensure that your footage met the technical requirements of broadcasters. Recollect, NTSC was instituted in the 1940s, (PAL appeared nearly a decade afterward). And so, making certain that your video would brandish properly on every television required a off-white amount of control. Additionally, there were limitations within the adequacy of analog and digital standard-definition recording engineering, every bit anyone who has severely overexposed parts of their images and suffered the horrific clip to nauseating xanthous can sadly adjure.
This necessity for rigorous command of exposure and colour required the employ of various pieces of gear—virtually notably the waveform monitor and the vectorscope. Don't feel as though yous have to run out and purchase one; many monitors—studio, field, and on-photographic camera, have these displays, as well as histogram functionality, built in. Y'all will also be able to find these scopes and displays in many NLE systems.
Waveform Monitor
The waveform monitor is used to evaluate the effulgence of your image, regardless of the color. The scale of the waveform monitor is 0 to 100 IRE. IRE represents the scale invented by the International Radio Engineers society. Essentially, information technology is designed to friction match the capabilities of early televisions to brandish an image. Anything at 0 is completely black, with no detail, and anything above 100 will be clipped and white, with no detail. With mod televisions and displays, peculiarly with HDR displays, it is possible to exceed the 100 IRE threshold and not clip your highlights; luminance values found in this region are oftentimes called super whites. All the same, the clip at 100 situation still exists, and exist aware that unless you are sure your mail production and delivery path tin can handle images with areas over 100 without clipping, literally cutting off any information in that part of the paradigm, it is safer to keep your images in the 0 to 100 IRE range.
Of interest to note about a waveform monitor display, equally opposed to a vectorscope or histogram, is that the waveform produces an abstract version of your paradigm; viewing the waveform from left to right mirrors viewing the image from left to right, making it easy to reference the brightness of specific areas of your paradigm/frame quickly.
Vectorscope
The vectorscope displays 6 color targets essentially stock-still into an odd-shaped pattern on a grid. In fact, each color is represented by 2 targets, merely what is important about the vectorscope is that information technology displays color information that the waveform monitor does not. In the old days of analog, the vectorscope, forth with the waveform monitor, were tools used to align multiple cameras, so that their colors and brightness matched when shooting the aforementioned set up. Specific colour charts were shot, and the technician would arrange the cameras to make sure that ruby-red on one photographic camera was the same ruddy on some other. This would be done by manipulating the camera electronically to make sure that the known color landed in the center of the target. Even in the digital age, or maybe especially in the digital age, with productions using a wide variety of cameras with different sensors from different manufacturers, being able to read your camera on a vectorscope is precisely what yous need. Getting your colors to align accurately when shooting will save y'all significant time in mail service, even if you lot are only working with one camera.
As far equally reading the vectorscope itself, there are two targets for each color (red, magenta, blue, cyan, green, and yellow—the chief and secondary colors) and you can set your scope to display at 100 or 75%. What this ways is that if your Vectorscope is set at 75%, then the target represents 75% saturation, and the further away from the centre of the display, the more saturated that color. At 100% setting, the target box represents 100%. By and large speaking, going above 75% saturation can be dangerous in terms of displaying colors that are outside broadcast prophylactic and not reproducible past all monitors. So knowing your entire post path, including final display format, is important; otherwise, peradventure it is all-time to err on the side of caution with both exposure and color.
Histogram
Histogram is a display that analyzes your image and displays the pct of luminance fleck values across the screen. And so, while you are scratching your head and trying to figure out what that judgement means, allow me try to explain it in simple terms. Unlike the waveform, which displays brightness vertically from nothing to 1 volt, the histogram displays luminance horizontally, darkest as in 0 at the left, and brightest as in 100 to the right. If you are working at eight-chip, the brandish would essentially be 0 to 255 values. All the same—and this is important—it isn't really displaying the real values; what it is showing you is the percent of the pixels in your image that are at the values, and rather than apply a pie chart, information technology uses something akin to a bar chart brandish. The weakness of this display is that it does not show you which parts of your prototype are nighttime or bright, merely how much of the total image is at each value.
If you wait at a histogram and the majority of the display is all the way over to the left or all the manner over to the right, this indicates that virtually of your image is either very dark or very bright. How does this differ from a waveform monitor? A waveform monitor volition allow you to see which part of your image is higher up 100, and thus clipped, assuasive you to place hot spots or exposure issues. The Histogram but shows a rough per centum of where your image is exposed. To get the almost out of your histogram, yous really will have to consider the shot itself. Is it supposed to be mostly night with a few highlights, as in a dark scene—nighttime, maybe? If so, then having the majority of your pixels over to the left may brand sense. Is your epitome generally bright, say an intentionally bright desert shot? Then it would brand sense that the majority of the pixels were over to the right. In either of those scenarios, it might brand sense to adjust your exposure some and exit yourself room in post to brand adjustments. So, using the histogram to aid you determine exposure and and then, adjusting your exposure to make certain that most of your information isn't either clipped at the right, or lost in the shadows to the left, tin be a valuable process.
While we are discussing exposure, call back that even in a dark scene, having stiff highlights or backlighting tin can help ascertain the shapes in the image, and tin can even assist bring a round, natural-looking depth to the composition, enhancing the dramatic outcome of your image. Besides, having a expert bright and nighttime reference is comforting to the eye, and it helps keep the eye-brain combo from making the image wash out to medium gray.
I promise you have institute this cursory introduction to waveform monitors, vectorscopes, and histograms useful. For more detailed info about reading histograms, check out our article, How to Read Your Camera's Histogram.
Source: https://www.bhphotovideo.com/explora/video/tips-and-solutions/introduction-waveforms-scopes-and-exposure
0 Response to "How to Read a Waveform for Video"
Post a Comment