Understanding aspect ratios

The aspect ratio specifies the ratio of width to height. Video frames have an aspect ratio (frame aspect ratio) as do the pixels that make up the frame (pixel aspect ratio). Some video camcorders can record various frame aspect ratios, and the NTSC and PAL video standards use different pixel aspect ratios. If an image of a circle appears oval‑shaped, there can be a mismatch between the aspect ratios of the image and your project.

Premiere Elements automatically attempts to detect and compensate for the pixel aspect ratio of source clips so that distortion doesn’t occur. If a clip appears distorted in Premiere Elements, you can manually change its pixel aspect ratio. It's important to reconcile pixel aspect ratios before reconciling frame aspect ratios. Misinterpretation of a source clip’s aspect ratio causes incorrect frame aspect ratio.

Frame aspect ratio

Frame aspect ratio describes the ratio of width to height in the dimensions of an image. For example, DV NTSC has a frame aspect ratio of 4:3 (or 4.0 width by 3.0 height). For comparison, a typical widescreen frame has a frame aspect ratio of 16:9; many camcorders that have a widescreen mode can record using this aspect ratio. Many films are shot using even wider aspect ratios.

A 4:3 frame aspect ratio (left), and a wider 16:9 frame aspect ratio (right)

When you add clips into a project with a different frame aspect ratio, decide how to reconcile the different values. You can show a widescreen movie with a 16:9 frame aspect ratio on a standard TV with a 4:3 frame aspect ratio in two ways. Use the Letterboxing technique to fit the entire width of the 16:9 frame into a black 4:3 frame. Black bands appear above and below the widescreen frame.

Alternatively, use the Pan and scan technique to fill the 4:3 frame with only a selected area of the 16:9 frame. Although this technique eliminates the black bars, it also eliminates part of the action. Premiere Elements automatically letterboxes any 16:9 footage that you add into a 4:3 aspect ratio project.

Pixel aspect ratio

Pixel aspect ratio describes the ratio of width to height in a single pixel of a frame. Pixel aspect ratios vary because different video systems make different assumptions about the number of pixels required to fill a frame. For example, many computer video standards define a frame that has a 4:3 aspect ratio as 640 x 480 pixels. Pixels that are square, which have an aspect ratio themselves of 1:1, perfectly fill the horizontal and vertical space the frame defines. However, video standards such as DV NTSC (standard for DV camcorders in the U.S.) define a 4:3 aspect ratio frame as 720 x 480 pixels. Consequently, to fit all of these pixels in the frame, the pixels must be narrower than the square pixels. These narrow pixels are called rectangular pixels, and they have an aspect ratio of 0.9:1, or 0.9 as they are commonly called. DV pixels are vertically oriented in systems producing NTSC video and horizontally oriented in systems producing PAL video. Premiere Elements displays a clip’s pixel aspect ratio next to the clip’s image thumbnail in the Project Assets panel.

If you display rectangular pixels on a square‑pixel monitor, images appear distorted, for example, circles distort into ovals. However, when displayed on a broadcast monitor, the images appear correctly proportioned because broadcast monitors use rectangular pixels. Premiere Elements exports clips of various pixel aspect ratios without distortion. It automatically adjusts the pixel aspect ratio of your project to the pixel aspect ratio of the clips. You can encounter a distorted clip if Premiere Elements interprets pixel aspect ratio incorrectly. Correct the distortion by manually by specifying the source clip’s pixel aspect ratio.

Pixel and frame aspect ratios

A. Square pixels and 4:3 frame aspect ratio B. Nonsquare pixels and 4:3 frame aspect ratio C. Nonsquare pixels displayed uncorrected on a square‑pixel monitor 

Capturing or adding various aspect ratios

Premiere Elements attempts to automatically compensate for pixel aspect ratios and preserve the frame size of added images. Images that you add are treated in the following ways:

  • Add video with D1 resolution 720 x 486 or DV resolution 720 x 480. Premiere Elements automatically sets the video’s pixel aspect ratio to D1/DV NTSC (0.9). For a footage with D1 or DV resolution 720 x 576, Premiere Elements sets its pixel aspect ratio to D1/DV PAL (1.067). However, it helps to see the Project Assets panel or the Interpret Footage dialog box to ensure that all files are interpreted correctly.

  • Premiere Elements automatically assigns pixel aspect ratios to files by using the Interpretation Rules.txt file in the Premiere Elements/Plug‑in folder. If a specific type of image is consistently misinterpreted (distorted), modify the entries in the Interpretation Rules.txt file. If you want to override the pixel aspect ratio interpretation for files already in a project, use the Interpret Footage command.

  • To change the size of a clip in Premiere Elements, select the clip and change the Scale property of the Motion effect. The Motion effect is available in the Properties view with the clip selected in the Expert view timeline.

View a project’s aspect ratio

The preset you choose when you start a project sets the pixel aspect ratio for the project. You can’t change the aspect ratio after it is initially set.

  • Choose Edit > Project Settings > General.

Adjust pixel aspect ratio for a still image or source clip

To combine diverse footage within a project and generate an output without distorting source images, ensure that all files are interpreted correctly.

Note:

When you set the pixel aspect ratio of a file, use its original ratio, not the ratio of the project and final output.

  1. In the Expert view, click Project Assets.
  2. Select the still image or source clip.
  3. Choose File > Interpret Footage.
  4. In the Pixel Aspect Ratio section, select Use Pixel Aspect Ratio From File to use the original ratio of the file. Alternatively, choose one of the following from the Conform To menu:

    Square Pixels

    Uses a 1.0 pixel aspect ratio. Use this setting if your source clip has a 640 x 480 or 648 x 486 frame size. You can also use this setting if the file was exported from an application that supports only square pixels.

    D1/DV NTSC

    Uses a 0.9 pixel aspect ratio. Use this setting if your source clip has a 720 x 480 or 720 x 486 frame size. This setting lets you maintain a 4:3 frame aspect ratio for the clip. Use this setting for clips exported from an application that works with nonsquare pixels, such as a 3D animation application.

    note: For more information about D1, see the Glossary in Premiere Elements Help.

    D1/DV NTSC Widescreen

    Uses a 1.2 pixel aspect ratio. Use this setting if your source clip has a 720 x 480 or 720 x 486 frame size. This setting lets you maintain a 16:9 frame aspect ratio.

    D1/DV PAL

    Uses a 1.0666 pixel aspect ratio. Use this setting if your source clip has a 720 x 576 frame size and you want it to maintain a 4:3 frame aspect ratio.

    D1/DV PAL Widescreen

    Uses a 1.4222 pixel aspect ratio. Use this setting if your source clip has a 720 x 576 frame size and you want it to maintain a 16:9 frame aspect ratio.

    Anamorphic 2:1

    Uses a 2.0 pixel aspect ratio. Use this setting if your source clip was amorphically transferred from a film frame with a 2:1 aspect ratio.

    HD Anamorphic 1080

    Uses a 1.333 pixel aspect ratio.

Use square‑pixel files in a D1 or DV project

You can use square‑pixel footage in a DV project and generate output that does not appear distorted. Premiere Elements either “upsamples” (increases) or “downsamples” (decreases) the resolution of a file that does not match the project frame size. Downsampling results in a higher‑quality image. Create files that are larger than the project’s frame size so that Premiere Elements need not upsample and enlarge them.

  • Prepare the file by using one of the following methods, and then capture or add the file to Premiere Elements:
    • If your final output is DV (NTSC), create and save it at a 720 x 540 frame size. Saving at this frame size prevents upsampling or 640 x 480 to prevent field distortion on a field‑rendered file.

    • If your final output is DV (PAL), create and save it at a 768 x 576 frame size. Saving at this frame size prevents upsampling and field distortion on a field‑rendered file.

    • If your final output is D1 (NTSC), create and save it at a 720 x 540 frame size.

    • The frame size of a square‑pixel image can match the frame size of your project (for example 720 x 480). However, if they have different pixel aspect ratios, redesign the image using a different frame size (such as 720 x 540). Redesigning is necessary when the application you use to prepare the file doesn’t support nonsquare pixels.

Set field options for imported interlaced video

In most video, each frame consists of two fields. One field contains the odd‑numbered lines in the frame, and the other contains the even‑numbered lines. The fields are interlaced, or combined, to create the complete image. Adobe Photoshop Elements includes a reverse field order preset for video imported from a hard disk or Flash memory camcorder that uses upper fields first. You can capture source footage with upper fields first. For this footage, ensure that your project uses either the Standard or Widescreen preset from the Flash Memory Camcorders presets folder.

Ordinarily, interlacing isn’t apparent to a viewer. However, each field captures the subject at a different time. Due to the time difference, playing a clip in slow-motion or creating a freeze frame makes the two fields discernible. You observe the same behavior when you export a frame as a still image. To avoid this situation, you can deinterlace the image. Deinterlacing eliminates one field and either duplicates or interpolates the lines of the remaining field.

Reversing the field dominance, the order in which the fields are recorded and displayed, can cause playback problems. When the field dominance is reversed, motion appears jerky because the fields no longer appear in chronological order. Fields are reversed when the original videotape’s field dominance is the opposite of the field dominance of the video‑capture card used to capture the clip. Fields are also reversed when the field dominance of the original videotape and the video‑editing software are opposite to each other. Reversing can also happen when you set an interlaced clip to play backward.

To avoid these complications, you can deinterlace the image. Deinterlacing eliminates one field and either duplicates or interpolates the lines of the remaining field. You can also set field options for an interlaced clip so that the clip’s picture and motion quality are preserved in certain situations. These include changing the clip speed, exporting a filmstrip, playing a clip backward, or freezing a video frame.

  1. Select a clip in the Expert view timeline, and choose Clip > Video Options > Field Options.
  2. Select Reverse Field Dominance to change the order in which the clip’s fields appear. This option is useful when the field dominance of the clip doesn’t match your equipment or when you play a clip backward.
  3. For Processing Options, select one of the following choices, and click OK.

    None

    Does not process the clip’s fields.

    Interlace Consecutive Frames

    Converts pairs of consecutive progressive‑scan (noninterlaced) frames into interlaced fields. This option is useful for converting 60 fps progressive‑scan animations into 30‑fps interlaced video because many animation applications don’t create interlaced frames.

    Always Deinterlace

    Converts interlaced fields into whole progressive‑scan frames. Premiere Elements deinterlaces by discarding one field and interpolating a new field based on the lines of the remaining field. It keeps the field specified in the Field Settings option in the Project Settings. If you specified No Fields, Premiere Elements keeps the upper field unless you selected Reverse Field Dominance, in which case it keeps the lower field. This option is useful when freezing a frame in the clip.

    Flicker Removal

    Prevents thin horizontal details in an image from flickering by slightly blurring the two fields together. An object as thin as one scan line flickers because it can appear only in every other field.

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