' Television: Critical Methods and Applications - Frame-Grab Tutorial


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Frame-Grab Tutorial
Written by Jeremy Butler   
Thursday, 02 November 2006
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Frame-Grab Tutorial
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Capturing Still Images

Which Software Should I Use?

Hardware such as capture devices and video cards rely on various types of software to capture still images. It's beyond the scope of this tutorial to describe them all, but we will explain two applications (one for Windows and one for Mac) and then provide guidance about the format of the still images they capture.

To skip directly to comments on image format, go to page five.

Capturing Still Images In Windows

The leading digital video editor that comes in a Windows version is Adobe Premiere Pro, but using it for still-image grabs is like crushing a cockroach with a sledgehammer. Fortunately, Adobe has released a slimmed-down, "lite" version of this program and called it Premiere Elements. While the "Pro" version will set you back about $850 ($300, if you're a student), you can find the Elements version for well under $100 -- often bundled together with Adobe Photoshop Elements. Students can even buy an "academic" version for $70. (All prices as of October 2006.)

Here's how to capture a single frame using Adobe Premiere Elements or, as we'll abbreviate it here, APE (not that anyone else calls it that):

  1. Follow the procedure outlined on page 3 to physically connect an analog video source (VCR or DVD player) to the computer.
  2. Before reading further you may want to click here -- or click the thumbnail image below -- to view APE's editing set-up in a separate browser window in order to follow along with the next steps.
    click for larger image
  3. Import a short clip into APE--including a few seconds on either side of the frame you want to grab. APE calls the importing process "capturing" video. Please refer to APE's documentation for more details, but here are the basics:
    1. Click the Get Media icon on the left.

      (Confusingly, there is also a similar icon up at the top, in the task bar. If you click it, you'll next click Capture.)
    2. Select the source of your video (DV Camcorder, if you're connecting via FireWire or USB)

      which will open the Capture Panel.
    3. In the Capture Panel, use the controls to cue the video to the spot you desire. Then click the Get Video and Stop Capture buttons to start and stop your capture.
    4. The new clip will be inserted into your project and appear in the Media panel in the upper left of the screen.
  4. Put the clip you want to use into what APE calls the "sceneline"--the part of the screen where you arrange video and audio to make a movie.

    We've put a clip from the classic driver's ed film Signal 30 in our sceneline. You must have the clip in the sceneline, and not just in the preview window, in order to grab an image.
    • Note: Most professional editing programs use timelines instead of scenelines. APE offers that option, but, in the case of frame grabs, it makes no difference if you use a timeline or a sceneline; and APE's default is the sceneline.
  5. Select a scene by clicking on it. It should appear in the Monitor panel in the top, middle of the screen.
  6. You may now use the Monitor's playback controls and/or the slider in the Monitor's mini-timeline to find exactly the frame you want.
  7. When you're satisfied that you've chosen the perfect frame, click into the File Menu, select Export, and Frame... (its keyboard shortcut is Ctrl-Shift-M).

    The Export Frame dialog box will open.
  8. The image format will probably default to BMP or Bitmap, as you can see in the Summary window of the Export Frame dialog box:

    This is fine and will save the frame at the highest quality possible. However, the frame will be rather large (approximately 1,000 kilobytes) and you may not need all that quality.
  9. If you want to save it in a format other than Bitmap, click the Settings button near the Summary window to pull up the Export Frame Settings dialog box

    By changing the File Type you may alter the format in which the image is saved. For many purposes -- including inserting into word processing documents and using on Websites -- the JPEG format is acceptable and will give you a much smaller file. You can compare/contrast the two files over here:
    Bitmap format (1,013 KB)
    JPEG format (51 KB)
    Although not readily apparent to the naked eye, the Bitmap-formatted file is of a higher quality than the JPEG-formatted file. To better see the difference, try enlarging both files in image-editing software.
    For more on formats, please see page 5 or the Wikipedia article, "image file formats."
  10. You've just created your first frame grab! Aren't you proud?
    Here's a reduced, thumbnail-sized version of our Signal 30 grab. Click it to see the full image.
    click for larger image

Quick-n-dirty alternative method with Premiere Elements:

Beginning with version 3 of Premiere Elements, you can skip the importing process and capture a frame directly from the video signal. It's part of a stop-motion animation feature first introduced in APE 3. APE's help system describes the process:

  1. Connect your device to your computer and turn it on.
  2. If capturing from videotape, place the device in Play, VTR, or VCR mode.
  3. Click the Get Media From button in the Media panel.
    Premiere Elements: Get Media button.
  4. Click the DV Camcorder, HDV Camcorder, Webcam button in the Media panel.
    Premiere Elements dialog box.
  5. APE opens the Capture panel, and opens the Available Media view of the Media panel. (Click image to enlarge.)
    APE Capture panel
  6. Click the Stop Motion button to change from regular "capture" to capturing one frame at a time.
    APE Capture panel detail: More button.
    Then click the Create New Stop Motion button to begin the frame-grabbing process.
  7. If you are grabbing frames from a digital video camcorder, you can use the player controls to find the frame(s) you want. If you are using the DV camcorder as a pass-through, or you're using some other external, FireWire capture device, you can view a preview of that video source in the Capture panel.
  8. Click the Grab Frame button whenever the Capture panel displays a frame you want to save to the hard disk.
    APE: capture panel detail, frame-grab button.
    Each frame you grab will appear as a Bitmap (BMP) file in the Available Media panel, with a sequential number in its filename, and also be saved to your hard disk.
  9. Voila! You've created a frame grab without first recording the video!

Capturing Still Images on a Mac

Since October 1999, Apple has released computers--including the lowly iMac--with video editing software pre-installed. This application, iMovie, can handle many simple editing tasks--including grabbing a frame.

To capture a single frame from an analog-video source (VCR, set-top DVD player) using iMovie:

  1. Follow the procedure outlined on page 3 to physically connect an analog video source (VCR or DVD player) to the computer using a FireWire or USB connection.
  2. Use iMovie to handle the importing process. A tutorial explaining this is available here.
  3. Before reading further you may want to click here -- or click the thumbnail image below -- to view iMovie's editing set-up in a separate browser window in order to follow along with the next steps.
    click for larger image
  4. If you've imported more than one clip, click on a single clip's icon to select it.

    In our sample, "NorthernExposure.mov" (truncated to "Norther...ure.mov") has been selected and appears in the iMovie "shelf" in blue. Note that you do not have to drag the clip to the timeline in order to grab a frame.
  5. Using the player controls, find the exact frame you wish to capture.

    In our sample, we've selected frame 00 at 31 seconds into a clip from Northern Exposure -- as indicated by the pointer on the blue line and the numbers, "31:00."
    Editing tip: the keyboard's arrow keys allow you to move the pointer more accurately than dragging the pointer around with a mouse.
  6. From the File menu, select Save Frame As...

    (Keyboard shortcut: Command-F)
  7. iMovie will default to saving the file in the Macintosh PICT format and sticking it on the desktop, which quickly results in a very cluttered desktop.

    And PICT is a virtually useless format. Change the format to JPEG (more about JPEG on page 5), give it a name you can remember, and save the file somewhere convenient.
  8. You have just created your first frame capture! Why not click this image to see it full sized?
    click for larger image
    Time to sit back and admire your newfound technological expertise.

Last Updated ( Monday, 24 September 2007 )
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