Scanning Versus Video, Different but Complementary Applications

We are often asked if it is better to use a scanner or a video or a still video camera to digitize pictures into the computer. And since a camera takes pictures, why not then, take a picture of a picture and save the cost of a scanner?

The answer is no (unfortunately), if you need to bring in a photograph or a printed illustration you must use a scanner.

To clarify the difference in performance between a video camera and a scanner we must examine the resolution of the video camera, the resolution of the scanner and the resolution of the computer screen. When you use a scanner, its optical element is typically capable to resolve (and represent) from 600 to 1200 dots per inch.

If your screen is, say, 10" high and you scan a 10" high picture, then the picture represented on your screen is composed of columns of 12,000 dots. On the other hand, the optical element of the video camera has, typically, 400 lines.

This means that whatever appears in the field of the camera lens will be represented by 400 lines. Hence, if your screen is 10" high (and you capture at full screen 640 x 480 pixels), the 400 lines of resolution are functionally equivalent to having scanned the picture, framed by the camera, at 40 dots per inch.

But then - we are asked at exhibitions, where we show both our scanners and our capture cards - why do the screen pictures look just as good whether they are scanned or video-captured? Because both the scanned and the video-captured images are displayed at the resolution of the screen. The resolution of the screen is essentially equivalent to the resolution of the video camera element.

The screen cannot match the higher resolution of the scanner. You may now ask why should we use a scanner if we cannot see the higher resolution? We can actually, when we enlarge the image or print an enlarged detail to a high resolution printer. The higher the resolution of the scanner the more accurate the magnified image.

A video-captured image will appear jagged when magnified, a scanned image will maintain smoothness and accuracy of rendition.

What are the advantages and disadvantages of one system versus the other? Scanning is indispensable for photographs and illustrations. You can achieve remarkable resolutions and, actually, use a scanner as an elegant image magnifier. Keep in mind, however, that an 8 1/2 x 11" picture scanned in color at 1200 dpi will swallow almost 1 Gigabyte of hard disk memory (let alone the time to scan).

1200 dpi is excellent for scanning, enhancing (and printing) details. Video-Capture is quick (1/30 sec), immediate, its memory requirements are moderate and lets you capture 3 dimensional objects. In conclusion, scanner and video-capture are complementary tools and, if you become serious about imaging you will justify using both.

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