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Advanced Segment Effects

Some segment effects don't share any parameters. Two of the segment effects are quite different from the others. They are the Color and Color Correction effects. The Color Correction effect acts more like a tool.

Color Effect

When you apply a color effect to a clip, you get access to a set of parameters unlike any other effect (see Figure 9.36). To apply a Color effect, open the Effect Palette, choose the Image category, and drag the Color Effect icon onto the clip you want to modify.

A few warnings about some of these parameters. If you are not hooked up to a Waveform Monitor or a Vectorscope, changing some of these values can move your video levels out of broadcast range. Let's simply go through the parameters as they appear in the Effect Editor.

• Luma Adjust This changes the brightness and contrast of the clip. The brightness increases and decreases the overall brightness and darkness of the image. The contrast adjusts the range, determining which values are white and which are black. (Avid Xpress Pro will not let you adjust these levels past the established values for NTSC video white, which is 100 IRE, and black, which is 7.5 IRE.)

• Luma Range These settings allow you to set how white your white is and how black your black is. Next to the Fast Menu, you'll see the range is set to 16235, which is set for standard NTSC video. The other option is 0255, which makes black as black as it can be and white as white as it can be. These values are for Luma keys, which are covered in the next chapter. The W point parameter defines the value within the image that will be white as the B point will define which values in the image display as black. The Gamma adjustment allows you to brighten and/or lighten the midtones of a clip.

• Luma Clip This allows you to set the limit of overall black and white values of your image that will display and output. Leave this set to the default values of 235 and 0. These are the black and white values for NTSC video.

• Chroma Adjust Chroma means color. These adjustments affect the color of the image. Hue adjusts the colors values on a color wheel. Saturation adjusts the overall intensity of the color. A saturation value of 100 makes the image black and white.

• Color Style These parameters create different kinds of effects. Post stands for Posterization. When you adjust the Post values, you are changing the gradations between tones. Try to avoid using this effect, as it is considered more of an amateur look. Solar stands for Solarization, which inverts the black and white values in a clip.

• Color Gain These parameters can add a tint of color to your image. The default value is 100.

Keep in mind that these adjustments provide effects, not corrections. If you need to correct the color of a clip, don't use the Color effect. Use the Color Correction effect instead.

The Color Correction Effect (Tool)

Avid Xpress Pro is equipped with one of the best color-correction tools in the industry as far as editing platforms are concerned . The inherit problem with video and film is attempting to make two shots from two different cameras match. Many times the lighting is different, the cameras are set up differently or the cameras are not even the same kind or format. Keep in mind; color correcting should be done with the assistance of a broadcast monitor (properly configured).

The Color Correction Mode

To perform color correction, you must first step into the Color Correction mode. The easiest way to do this is to choose Color Correction from the Toolset menu. When you choose this toolset, the entire layout of the screen changes. Three windows are displayed: the Composer window, the Color Correction tool, and a resized Timeline (see Figure 9.37).

The three screens in the Composer window can be changed to display different media or video scopes. If you click on the word above the first monitor, you'll open a pull-down menu (see Figure 9.37). The idea here is that you need to refer to other scenes to match certain colors.

Your options are as follows :

• Entire Sequence This option makes the entire sequence available to be viewed in this monitor. This is very useful when you need to navigate to a certain clip that you want to use as a reference color that is perhaps far away from the clip you need to adjust.

• Reference This locks the current frame in the monitor. As you make changes in the other monitors, any monitors set to reference will not update. The monitor becomes a reference shot for you to match colors to.

• Current This option only plays the current segment in the Timeline that the Position Indicator is parked on.

• Previous This option displays the segment just before the clip you're making adjustments to.

• Next The segment next to the segment you're adjusting is displayed.

• Second Previous This option displays the segment two segments before the current one.

• Second Next This option displays a segment that is two clips from the segment you're adjusting.

Step through each of these options and view the different frames and media that can be displayed.

Video Scopes

The second set of options is video scopes. This chapter covers two basic scopes used in all video production: the Waveform and Vectorscope. Although Avid Xpress Pro certainly offers a variety of different scopes, learning these two fundamental scopes will assist you in understanding how video information is displayed technically.

Scopes are the only way to really tell if a video signal is set up for broadcast values. Never simply use your eyes. They will mislead you. A color that you think is displayed within a safe zone might actually be too bright. Let's explore a couple of the different scopes that you'll use when monitoring both the Chroma (color) and the Luminance (black and white) of an image.

The first scope you'll explore is the Waveform Monitor. Avid Xpress Pro gives you two monitors to view: the Y Waveform and the YC Waveform. You'll use the Y waveform for monitoring. The Y Waveform only monitors the Luma information of a clip (the brightness of the clip, or how white the white is). If you display color bars in this monitor, you'll notice that the optimum white values should be 100% IRE for an NTSC image and 235 for a digital image (see Figure 9.38).

The darkest part of an image (the parts that are black) are also displayed in this scope. Images should not be below 7.5 IRE for NTSC. or 0 on this scale, and 16 for a digital signal. Let's look at an actual image and see how it's displayed in the Y Waveform (see Figure 9.39).

In Figure 9.39, notice how the pool sign is very bright, which is reflected in the waveform. You definitely need to adjust this. Also notice that the overall black level is high. There really are no nice "black" levels in the image. You will adjust all these levels shortly, but for now, let's explore another scope you'll use for color correction, the Vectorscopes.

The Vectorscopes displays the color information in an image. If you monitor standard SMPTE color bars, the scope will display each color in its appropriate setting. The small squares represent colors, R (Red), MG (Magenta), B (Blue), CY (Cyan), G (Green), and YL (Yellow). See Figure 9.40. This graph displays how red, green, and blue blend together in an image.

Let's monitor a video image with this scope. Notice the scope in Figure 9.40 tells you that the image has a lot of blue. If the blue in the video was due to a poor white balance for a camera, you could make the necessary adjustments to lessen the amount of blue value in the image.

Color Correcting Using the HSL Group

The Color Correction effect gives you several options when making adjustments to a scene or clip. The first mode you'll dive into is the HSL group. HSL stands for Hue, Saturation, and Luminance. If you click on the HSL tab inside the Color Correction tool, you'll notice two tabs inside this modeControls and Hue Offsets (see Figure 9.41).

Let's start by adjusting the controls within the HSL group. Click on the HSL tab and the Controls sub-tab. Turn off the Hue Offsets for now. The four adjustments are Hue, Saturation, Brightness, and Contrast. To make an adjustment to a scene, park the Position Indicator on a frame of the clip that represents perhaps the worst part of the scene. Let's go back to the swimming sign, for example. By adjusting the brightness and contrast, you can lower how bright the shot is and add some blackness to the shot. If you monitored the adjustments in the waveform, you'd see that the image is in much better condition now than before the corrections. To make adjustments, simply drag the slider buttons , click in the text box and type in a value, or use the arrows on each side of the slider to make slight adjustments (see Figure 9.42).

Setting the White and Black Points

To make correct color corrections, you need to set the black and white points of an image. The black point is also referred to as the setup of an image and the white point as the gain value of an image. Setting the black and white points is simply a way of making sure the blacks in an image are as dark as they can be and the whites are as bright as they can be.

To set the black point, follow these steps:

1. Place the Position Indicator on the clip you want to adjust and find a frame in the clip that has nice dark black areas or shadows.

2. Make sure the center monitor is set to Current. Set the first monitor to Y Waveform.

3. Click the HSL tab and the HUE Offsets tab.

4. On the far right side of the Color Correction tool, you'll see three sliders that can be adjusted. They are Gain, Gamma, and Setup. Remember, setup is the blackness of the image (see Figure 9.43).

   Figure 9.43. The three sliders that can be adjusted are Gain, Gamma, and Setup.

5. Using the Y Waveform as your guide, adjust the Setup values until they near 0. Do not go below 0.

6. You have now set the black point on that clip or segment.

NOTE

NOTE

There are a few methods for comparing the image to how it looked before the correction. The first method is to turn on the Dual Split button under the monitor that is displaying the image (see Figure 9.44). This divides the screen into two, displaying the before and after results. I simply leave this button on all the time to see the differences. The other method is to click on the Enable button. By toggling this button on and off, you can see the results appear and then disappear (see Figure 9.45).

To adjust the white point, simply follow the same steps for setting the black point, but this time use a frame with a good white value and adjust the gain until it peaks at white. Do not go over 100.

The middle slider, Gamma, sets up the values between black and mid-grey and white and mid-grey. Large changes in the Gamma of a picture either add too much gray or not enough gray. However, slight adjustments in the Gamma can make an image "pop" by adding a slight contrast or brightness to a shot.

Hue Offsets

The Hue Offsets allow you to control a specific hue in a shot. The three wheels represent the Hue values of the shadows, midtones, and highlights. To adjust the hue values, click on the center cross on the portion of the image you want to change. If you want to add a "tint" to the shadows, click on the shadow wheel and move the middle cross. The farther you move this from the center, the more saturation you add. As you rotate around the circle, you change the overall hue inside that part of the imagethe shadows (the dark parts of the image), the midtones (the gray areas or common color areas), or the highlights (the bright areas of the shot).

Color Correcting Using the Curves Group

Another way to color correct a scene is to use the Curves group. Click on the Curves tab inside the Color Correction tool to view the color curves (see Figure 9.46).

The Curves group allows you to make adjustments to color by placing and adjusting control points. The default curve is a 45-degree straight line. If you add points and adjust the points below the 45-degree angle, the image darkens , above the 45-degree line and the image becomes lighter. The Master Curve allows you to affect the overall brightness of the image. To add a point on the curve, simply click in the color curve you want to adjust.

To make adjustments using these curves, click on the control point in the center and drag the control point up/left to increase the gamma or down/right to reduce the gamma of that particular color.

To reduce the overall gain, drag the control point straight up or down.

Saving the Color Correction Effect to a Bin and a Bucket

After you have made all your adjustments, you can save an effect either to a bin or to a bucket. When you save an effect to the bin, it is saved permanently. If you save it to a bucket, it is only saved until the end of your edit session. A bucket acts as a temporary place to store color correction effects.

To save a color correction effect to a bin, drag the color effect icon in the Color Correction tool to a bin and give it a very detailed name .

To save a color correction to a bucket, Option-click (Macintosh OS) or Alt-click (Windows) a bucket (see Figure 9.47).

The current color correction effect will be added to that bucket. To add to another scene, simply move your Position Indicator to the new scene and click on bucket number (C1, C2, C3, or C4). It will be added to the clip in the sequence.

Pan and Zoom Effect

One of Avid Xpress Pro's newest and coolest features is the Pan and Zoom effect. This effect allows you to import a still image much larger than the frame size you're working in (see Figure 9.48). After you import the image, you can pan across it or zoom in and out of it without the picture becoming pixilated.

The process of zooming and panning on an image was previously left to third-party plug-ins. Now, with Avid Xpress Pro, it's built right in the Effect Palette.

The steps to use the Pan and Zoom effect are slightly different than the standard segment effect. You first need to edit in a clip that acts as a placeholder. The clip you use as a placeholder is then exchanged with the higher resolution image. To import an image and pan and zoom around it, follow these steps:

1. Edit a clip (any clip; it will be changed) in to the Timeline where you want the effect to happen.

2. Apply the Pan and Zoom effect to the clip. Pan and Zoom is found in the Image category in the Effect Palette.

3. Open the Effect Editor on the Pan and Zoom effect and click on the Other Options button in the upper-left corner of the Effects Editor (see Figure 9.49). A window will open allowing you to navigate to the image.

   Figure 9.49. To load an image, click on the Other Options button in the Effect Editor.

4. Find the image and click the Choose button. The still image replaces the clip and appears in the Composer window.

5. While you're still in the Effect Editor, change the first parameter, Display, to Target.

6. To zoom in on the image, adjust the Size slider. To pan around the image, use the Position sliders. Don't forget to select keyframes when you make these adjustments.

The Velocity parameter adjusts how the image moves from keyframe to keyframe. For a smoother look, choose Spline instead of Linear. How the effect is rendered is determined through the Filter In Fast Menu. In general, the farther down the list, the better the quality but also the longer the render time (see Figure 9.50). It's best to experiment with each setting until you get the results you like.

The Advanced parameter allows you to inform Avid Xpress that the image has square pixels and you can select its color information, either RGB or 601. Refer to Chapter 2 "Capturing and Importing," for an explanation of the difference between RGB and 601 color levels.