The Histogram panel contains a number of tools to help you evaluate your photos exposure and even begin making adjustments. The most visible part of the panel is the histogram itself, which is simply a graphical representation of all of the tones contained in your photo, from the darkest tones on the left to the brightest tones on the right. However, in a possible jab at its rival, Adobe said that “unlike existing histogram-based solutions, the new technology in Premiere Pro was built with machine learning, helping users to save time. The Luma Histogram displays the range of luminance levels in the video signal, with black on the left and white on the right. When used with Adobe Premiere Pro or Adobe Prelude, ScopeLink will transmit 8bit Rec. 709 signals, and ScopeBox will.

Note:

Starting with the June 2015 release of Premiere Pro CC, vectroscope, and waveform monitors are replaced with new Lumetri Scopes. For more information see Lumetri Scopes.

Premiere Pro has a vectorscope and waveform monitors (YC Waveform, YCbCr Parade, and RGB Parade) to help you output a video program that meets broadcast standards and make adjustments based on aesthetic considerations, such as color corrections.

For decades, video production and duplication facilities have used waveform monitors and vectorscopes to accurately evaluate video levels—specifically, color and brightness.

A vectorscope measures the chrominance (color components) of a video signal, including hue and saturation. A vectorscope maps a video’s color information onto a circular chart.

The traditional waveform monitor is useful in measuring the brightness, or luminance component, of a video signal. In Premiere Pro, the waveform monitors can also display chrominance information. The waveform monitor works something like a graph. The horizontal axis of the graph corresponds to the video image from left to right. Vertically, the waveform displays the luminance levels, and optionally, the chrominance levels.

You can view a vectorscope, YC waveform, YCbCrParade, and an RGB Parade scope either individually or grouped inthe Reference Monitor, Program Monitor, or Source Monitor.

Depending on whether you want to view a scopefor a master clip or sequence clip, do one of the following:

• Double-click the clip in the Project panel.

• In a Timeline panel, position the playhead in thesequence you want.

(Optional) Choose Reference Monitor from the Window menuif you selected a clip in a Timeline panel.

Choose any of the following from either the ReferenceMonitor, Program Monitor, or Source Monitor menu:

Displays the Vectorscope, YC Waveform, YCbCr Parade,and RGB Parade scopes in one monitor.

Displays a vectorscope for viewing the chrominance inthe video.

Displays a waveform monitor for viewing luminance andchrominance information.

Displays a scope with luminance (Y) and color difference(Cb and Cr) information.

Displays a scope showing the red, green, and blue componentsin the video.

Displays the Vectorscope, YC Waveform, and YCbCr Paradescope in one monitor.

Displays the Vectorscope, YC Waveform, and RGB Paradescope in one monitor.

The Vectorscope displays a circular chart, similar toa color wheel, that shows the video’s chrominance information. Saturationis measured from the center of the chart outward. Saturated, vividcolors produce a pattern some distance from the center of the chart,while a black-and-white image produces only a dot at the centerof the chart. The particular color, or hue, of the image determinesthe direction (angle of the pattern). Small target boxes indicatewhere fully saturated magenta, blue, cyan, green, yellow, and red(present in a color bars test pattern) should appear. In NTSC video,chrominance levels should not exceed these target areas.

Adjusts the brightness of the pattern display. It does notaffect the video output signal.

Default position. Use to check video input in which standard75% intensity bars, like those in Premiere Pro, are used.

Shows the entire range of video signal chrominance. Use withvideo input containing 100% intensity bars.

The YC Waveform displays a graph showing the signal intensity in the video clip. The horizontal axis of the graph corresponds to the video image (from left to right) and the vertical axis is the signal intensity in units called IRE (named for the Institute of Radio Engineers).

The YC Waveform displays luminance information as a green waveform. Bright objects produce a waveform pattern (bright green areas) near the top of the graph; darker objects produce a waveform toward the bottom. For NTSC video in the United States, luminance levels should range from 7.5 to 100 IRE (sometimes referred to as the legal broadcast limit). Japan’s implementation of NTSC standards permits a luminance range from 0 to 100 IRE. Generally, luminance and chroma values should be about the same and distributed evenly across the 7.5 to 100 IRE range.

The YC Waveform also displays chrominance information as a blue waveform. The chrominance information is overlaid upon the luminance waveform.

You can specify whether the YC Waveform displays both luminance and chrominance information, or just luminance information.

Adjusts the brightness of the waveform display. It does notaffect the video output signal.

Displays a waveform that approximates the final analog video outputsignal. Deselecting this option displays the digital video information.

Displays both chrominance in addition to luminance information. Deselectingthis option displays only the luminance.

The YCbCr Parade scope displays waveforms representinglevels of the luminance and color difference channels in the videosignal. The waveforms appear in a graph one after another.

Histogram In Premiere Project

The Intensity control adjusts the brightness of the waveforms.It does not affect the video output signal.

Note:

Cb and Cr are the color difference channels in a digital videosignal. Cb is blue minus luma and Cr is red minus luma. Y representsluma.

The RGB Parade scope displays waveforms representingthe levels of the red, green, and blue channels in a clip. The waveformsappear in a graph one after another, in parade fashion. This scopeis useful for viewing the distribution of the color components ina clip. The levels of each color channel are measured proportionatelyto each other using a scale of 0 to 100.

The Intensity control adjusts the brightness of the waveforms.It doesn’t affect the video output signal.

The Histogram Is Your Guide

You can use the bar chart (also known as a histogram) at the top of the Levels dialog box to determine whether the adjustments you're making are going to harm the image or improve it. The histogram indicates which shades of gray your image uses and how prevalent those shades are within the image. If you find a gap in the histogram, you can look at the gradient directly below it to see which shade of gray is missing from your image.

By looking below the left side of the histogram, you can determine the darkest shade of gray in the image. By looking below the right end of the histogram, you can determine the brightest shade of gray in the image. If you look at Figure 4.7, you might notice the image contains no pure blacks or pure whites. The darkest shade of gray is about 95%, and the brightest shade is about 6%.

Figure 4.7 Look at the gradient bar directly below the ends of the histogram to determine the brightest and darkest shades present in the image.

There is no ideal when it comes to a histogram; it's simply a representation of which shades of gray are most prevalent in your image (Figure 4.8). The peaks indicate a shade of gray that takes up a lot of space in the image, and the valleys indicate a shade that isn't very prevalent in the image. A histogram that extends all the way across the space available and does not have tall spikes on either end indicates an image that has the full range of shades available, and is usually a sign of a good scan or a well-adjusted image.

Figure 4.8 Each image will have its own unique histogram.

Evaluating and Adjusting Contrast

The brightest and darkest areas of your computer monitor are nowhere near as bright or dark as the objects you'll find in the real world. The difference is even more extreme when you look at the brightest and darkest areas of a printed brochure—the paper is actually pretty dull, and the ink isn't all that dark. Because of this, you'll need to use the full range of shades from black to white in order to make your photos look as close to reality as possible.

By adjusting the upper-right and upper-left sliders in the Levels dialog box, you can dramatically improve the contrast of an image and make it appear more lifelike. When you move the upper-left slider in the Levels dialog box, you force the shade of gray directly below it and any shade darker than it (see the gradient) to black. So moving that slider until it touches the first bar on the histogram forces the darkest shade of gray in the image to black, which should give you nice dark shadows.

When you move the upper-right slider, you force the shade that appears directly below the slider and any shade brighter than it to white. So, similar to dark colors, moving the right slider until it touches the last bar on the histogram forces the brightest shade of gray to white, which should give you nice white highlights.

By adjusting both sliders, your image will use the full range of shades available to a grayscale image (Figure 4.9). If you move the sliders past the beginning and end of the histogram, you will get even more contrast, but you risk losing important detail in the process.

Figure 4.9 The shades that are beyond the upper-right and upper-left triangles become pure black and pure white.

Hidden Features to the Rescue

Histogram In Premiere Pro After Effects

To achieve maximum contrast without sacrificing detail, Adobe created a hidden feature in the Levels dialog box. It's known as Threshold mode. This feature allows you to see exactly which areas are becoming black or white, and it's the key to ensuring that you don't sacrifice detail. To get to the hidden feature, hold down the Option/Alt key when you move the upper-right or upper-left sliders in the Levels dialog box.

When you move the upper-left slider with Threshold mode turned on, your image should turn white until the slider touches the first bar on the histogram; then small black areas should start to appear. These are the areas that will become pure black. With most images, you'll want to make sure you don't force a large concentrated area to black, so move the slider until only small areas appear. You also want to make sure the areas that are becoming black still contain detail. Detail will show up looking like noise (not the kind you hear—the kind you see on an old television when you don't have an antenna hooked up), so make sure those small areas also look noisy. You'll need to repeat this process with the upper-right slider to make sure you get optimal contrast (Figures 4.10 to 4.14).

Figure 4.11 Upper-left slider adjusted way too far.

Figure 4.12 Large areas of the image are losing detail and becoming pure black.

Figure 4.14 Small areas become black but still contain detail (noise).

Three things might cause an image to have large areas of black or white from the start:

1. Your scanner isn't capable of capturing good shadow detail.
2. The image simply didn't have any detail in the shadows to begin with.
3. The image has been adjusted without using Photoshop's Threshold mode.

The Histogram Gives You Feedback

After you have applied an adjustment to your image, you can see an updated histogram by choosing Image > Adjustments > Levels again. Notice that after adjusting the upper-right and upper-left sliders, the histogram stretches all the way across the area available. It's just like stretching out a Slinky—you remember, 'It walks downstairs, alone or in pairs' (Figure 4.15). As you pull on the ends of the Slinky, the loops stretch out and start to create gaps. The same thing happens to a histogram—because Photoshop can't add more bars to the histogram, it can only spread out the ones that were already there. And remember, gaps in the histogram mean that certain shades of gray are missing from the image. So the more you adjust an image using Levels, the more you increase the possibility that you'll lose some of the smooth transitions between bright and dark areas (Figure 4.16).

Figure 4.16 After adjusting the top two sliders, your image should use the full range of shades available.

If you see large spikes on either end of the histogram (Figure 4.17), it's an indication that you've lost detail. That's because you forced quite a bit of space to white or black using Levels. But you'd know you did that, because you used the hidden feature, right? Or maybe you couldn't control yourself and used that Brightness/Contrast dialog box, where you can't tell if you damaged the image! You might also get spikes on the ends of the histogram (Figure 4.18) if you scan an image with too high of a contrast setting or a brightness setting that is way too high or low, or if your scanner isn't capable of capturing enough shadow detail.

Figure 4.17 Spikes on the end of a histogram usually indicate lost detail.

Adjusting Brightness

After you have achieved good contrast, your image might look too bright or dark. The middle slider in the Levels dialog box can fix that. (Techies love to call this slider the Gamma setting, but we plain folks call it the midpoint.) If you move the middle slider to the left, the image becomes brighter without messing up the dark areas of your image. Black areas stay nice and black. Or you can move the middle slider to the right to darken the image without messing up the bright areas. White areas stay bright white (Figure 4.19). This is the one setting that is a personal choice. I can't tell you how bright or dark your image should be.

Figure 4.19 Effects of the middle slider.

If you want to know what this adjustment is doing, just look directly below the middle slider; the shade of gray there will become 50% gray. Moving it to the left brightens your image because you'll be shifting what used to be a dark shade of gray to 50% gray. Moving the middle slider to the right darkens your image as you shift a bright shade to 50% gray. If you look at an updated histogram of the image, it will look like you stretched out a Slinky, then grabbed one side and pulled it to the middle (Figure 4.20). Some bars will get scrunched (is that a technical term?) together, whereas others get spread apart.

Figure 4.20 The adjustment shown on the left results in the histogram shown on the right.