Real-World Cameras vs. CG Cameras (Title Sequences in Production: The Camera and the Edit) (Motion Graphic Titling) Part 2

Speed and Frames Per Second

To better understand the concept of speed, imagine that your film or video camera is a still camera that takes a specific number of pictures every second. The number of images photographed each second is referred to as the frame rate and is measured in frames per second (fps).

You’ll need to determine the fps whether you use a video or film camera (where the fps of your camera determines the speed at which the camera advances and records each frame) or whether you start a project in After Effects or Motion (where the frame rate of your project determines how quickly frames are played back).

A film camera’s default recording speed is 24 fps, but internal or external devices, such as intervalometers or speed controls, allow recording at different frame rates.

A video camera’s default recording speed is 29.97 fps in NTSC (the video standard defined by the National Television Standards Committee) systems and 25 fps in PAL (Phase Alternating Line, the interlaced video format used by many European countries) systems. Also note that an increasing number of camera models offer the user the option to record at variable frame rates (for example, the Panasonic HVX-200 can record between 12 fps and 60 fps).

CG cameras don’t generally have a frame rate property. To change the frame rate, you’ll need to change the frame rate of your project. In After Effects you can set or change the frame rate of your project by choosing Composition | Composition Settings.

Figure 6.9 in after effects you can set or change the frame rate of your project by choosing composition composition Settings and change your Frame Rate value.

In Motion you can set your project’s frame rate by choosing File | New and selecting Custom from the project preset pull-down. Common frame rates are shown in Table 6.2.

Figure 6.10 in motion you can set your project’s frame rate by choosing File | new and selecting Custom from the project preset pull-down.

Table 6.2 Common Frame rates

24 fps	Film, certain HD formats, and certain SD formats use this frame rate; this can also be 23.98 fps for compatibility with NTSC video
25 fps	SD PAL
29.97 fps	SD NTSC
59.94 fps	720p HD video frame rate; this can also be 60 fps

Compressing and Expanding Time

Recording at speeds other than the default speed creates a temporal effect that changes how the moving image is perceived. The following are two common situations in which you will perceive a time compression or expansion:

•    Slower frame rates (e.g., 9, 12, 16 fps) produce fast-motion shots. In fact, if the playback frame rate is higher than the recording frame rate, the action will appear to move faster. For example, images recorded at 12 fps (low frame rate) and played back at 24 fps will create a fast-motion effect. In this case it will take 1 second to play back 2 seconds of recorded material. Think of the early silent films, which were shot at 18 fps and played back at 24 fps, creating that typical fast-walking movement a la Charlie Chaplin.

•    Faster frame rates (e.g., 36, 48, 60 fps) produce slow-motion shots. If the playback frame rate is lower than the recording frame rate, the action will appear to move slower. For example, images recorded at 48 fps (high frame rate) and played back at 24 fps will create a slow-motion effect. In this case it will take 2 seconds to play back 1 second of recorded material.

Figure 6.11 Slow-motion and fast-motion shots.

Time Remapping and Variable Frame Rates

In shooting footage for your title sequence, it’s important to identify the shots that might need to be recorded at higher frame rates well ahead of time, ideally during the preproduction of your project. Unfortunately, that doesn’t happen as often as one would like it to. At the editing table, when someone might ask, “Wouldn’t it be great if we had a slow-motion (or a time-lapse) here?" Wouldn’t it be great if you could say, “Sure! Let’s do it?" Here are three common scenarios and ways of changing frame rates in postproduction:

•    If you speed up a shot or create a time lapse in postproduction, you won’t really lose any image quality or information. For example, if you shot a hummingbird at 24 fps and you decide to speed it up to 12 fps, you would just have to cut one frame from every two and wouldn’t actually have any picture playback quality loss. Luckily, tools such After Effects allow you to conform the current frame rate of a video to a lower one (see the following figures).

•    On the other hand, if you tried to create a slow-motion effect after you recorded the images at a default frame rate (e.g., you shot your hummingbird at 24 fps and you decide to slow it down to 48 fps), you’ll have to duplicate (rather than cut) your frames, which could potentially be problematic and create some stutters in the playback. Once again, After Effects comes to your aid by allowing you to conform the current frame rate of a video to a higher one (see the following figures).

•    Finally, if you want to play your video at your recorded frame rate, then create a slow-motion effect, and then return to normal playback speed (e.g., you play back your hummingbird at normal speed and right when it’s reaching the flower’s nectar, you create a slow-motion effect, and then return to the regular frame rate playback), you can do so using variable frame rates in postproduction with After Effects’ and Motion’s Time Remap features (see the following figures).

Figure 6.12 in after effects you can conform your video clip to a higher or lower frame rate by choosing File interpret Footage Main from the menu.

Figure 6.13 To access the Time remap feature in after effects, first select your video layer, then choose layer Time Enable Time Remapping. click on the Graph Editor icon in your Timeline to display the Graph editor and modify the velocity curves and keyframes.

Figure 6.14 In Motion you can access the Time remap feature through inspector Properties tab Timing, where you can select Constant speed from the Time remap pull-down.

Figure 6.15 in motion you can access the Variable Speed Time remap feature from the inspector | Properties tab, were you can also pick the powerful Frame Blending option called optical Flow. Different from a motion-blur frame-blending algorithm, motion’s optical flow algorithm determines the application of the blur on the extra frames created by the slow-motion effect by analyzing the clip’s directional movement of the pixels. The result is a significant increase in the image quality of the slow motion.

Figure 6.16 in motion the velocity curves and keyframes can be modified in the Keyframe Editor tab in the timing pane.