Getting Rid of Video Scan Lines in Photoshop

Do you wish you had a “motor drive” camera that could capture multiple still images in rapid succession, letting you analyze your golf stroke or provide a selection of images to choose from? While many digital still cameras and some film cameras have multishot modes, your video camera can also do the job. All video cameras capture the equivalent of 30 still frames per second. All you need to do is extract the individual pictures you want with a video card in your computer that includes a frame grabber. You can also pause a video image on your television and shoot a still picture with your camera on a tripod or other sturdy support. Unfortunately, you also probably capture a set of dark horizontal lines known as video scan lines. They’re produced as the television or monitor display “paints” an image on your screen line by line, one full screen each 1⁄30 of a second.

Actually, that description is not quite true. Most video displays provide an interlaced picture, drawing odd-numbered lines in one pass and even-numbered lines in a second pass. Our eyes merge these two interlaced images into one, and combine successive frames to produce the illusion of motion. Photoshop allows you to take advantage of the interlacing phenomenon to remove those pesky scan lines. It can create a new, line-free picture by ignoring either the odd-numbered or even-numbered scan. One set is often enough to create a smooth image. In the steps that follow, I use a Photoshop De-Interlace filter to create such an image. Just follow these easy steps:
1. With a photograph in need of deinterlacing open in Photoshop, choose Filter-->Video-->De-Interlace.
2. Select the Odd Fields button in the Eliminate area of the De-Interlace dialog box.
You can use either button in most cases. The exception is when your original image happens to already be non-interlaced, as was the case with older video monitors. You’ll know when that happens — if you choose the “wrong” field, you end up with a totally black image because that set of scan lines didn’t exist.
3. Select the Interpolation button in the Create New Fields area.
With interpolation, Photoshop looks at the odd-numbered (or evennumbered, if you chose that option) scan lines on either side of a line being processed, and creates a new line of pixels that is an average of the three lines examined. This usually produces better results and smoother transitions than simply duplicating each line.
4. Click OK to apply the filter.
5. You may have to adjust the brightness and contrast of the photo to produce the best image.