Scopes, a creative trilogy

Paul Issacs

Author: Paul Issacs

Published: 07 December 2016

Scopes, a creative trilogy

The purpose of color correction is to fix any problems with exposure and color, ensuring the final image looks right. Color grading is used to set the mood by adjusting the colors of the video imagery to achieve a certain look or feel. At the core of color correction is tonal range: the range of brightness from dark (black) to light (white). When the tonal range is narrow, imagery will lack contrast and appear flat. Increasing the range will increase the contrast, providing brighter whites and deeper, darker blacks. This contrast often helps increase color saturation and can make a shot appear more vibrant.

Professionals often use cameras to record log-format video, which allows for greater dynamic range and exposure detail to be captured in shadows and highlights for a given video bit depth. This requires that, while on set, having a quality monitor with precision scopes to properly analyze the video signal is even more vital.

There are a number of widely used exposure monitoring tools available today. Zebras and false colors are excellent for quickly identifying areas of over- or under-exposure and for setting an approximate correct exposure for skin tone. For more accurate monitoring of exposure and color balance, it is preferable to use scopes of which there are three commonly used varieties -waveform, histogram, and vectorscope.

Waveform is a tool designed to check and aid in the setting of exposure levels, both for brightness and color. Its vertical scale provides more accurate exposure level measurement than false colors or zebras. A monitor\'s waveform can have three modes: luma, RGB overlay, and RGB parade. Regardless of mode, the waveform is a scope ideally suited for avoiding over-saturation of colors and checking exposure of skin tone, as well as consistent background lighting. It is also useful to ensure background separation on green screen shots.

Histogram is a tool for checking overall brightness (luma) or color level (chrominance) within an image. It displays how many pixels there are at each brightness or color level. Like waveform, the histogram can have three modes- luma, RGB overlay, and RGB parade. It can be used to quickly determine whether the full dynamic range is being captured. In other words, most pixels should be distributed broadly around the center of the horizontal axis. Too hard to the left, and the image is underexposed. Too hard to the right, and the image is overexposed.

Vectorscope is a circular graphical tool for monitoring color saturation and hues. It may be used to help make creative choices on overall look, eliminate unwanted color casts (offsets), and check white/black color balance. It\'s also a crucial tool for ensuring that color saturation falls within a legal broadcast color gamut. While modern HD televisions can handle the full tonal range (for 8-bit, RGB 0,0,0 to 255,255,255), there are still specifications for "broadcast safe colors\" that remain in effect worldwide and limit the range to 16,16,16 (safe black) to 235,235,235 (safe white). On a monitor\'s vectorscope, color saturation is determined by the distance from the center of the scope; the greater the saturation or more vivid a color, the further its trace reach is from the center. Color hue is determined by the direction or angle of the trace. Small boxes represent target values for fully saturated REC 709 primary and secondary colors. There is also a line, between the red and yellow target boxes that indicates skin tone.

With today\'s fast-paced, ever-evolving industry, a high-quality monitor with scopes is crucial for any professional to have in their arsenal. Proper color correction, with the application of the right scopes, can help to bring any video imagery to life.

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