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UnderColor, Volume 1, Number 2, December 25, 1984

  • Title: Review
  • Author: empty
  • Synopsis: Video Digitizers Compared
  • Page Scans: Link


GRAFX Digitizer


POB 254

West Mifflin, PA 15122


Digisector 69

The Microworks

POB 1110-A

Del Mar, CA 92014


Computize Digitizer

Computize Inc.

POB 207

Langhorne, PA 19047


Recently I had the opportunity to compare the three video digitizers that are or will be available for the Color Computer.

The Grafx digitizer is the least expensive of the three. It communicates with the Color Computer via the RS—232 port, taking about three seconds to digitize a single frame. The subject must be stationary during this time. I’ve seen two disks of pictures made with this digitizer, and am impressed with its ability to digitize very contrasty objects, such as block letters and cartoons. When using it on a face, one runs into the problem of the long exposure needed to produce a picture, and also the problem that its ability to show gray levels is somewhat limited. Improvements in software may help this problem somewhat. I would recommend the Grafx digitizer for users who want a low cost way to transfer large letters or black and white drawings into the computer. It is the least suitable of three products for use with live subjects. To effectively use it, you really do need a video monitor dedicated to monitoring the video signal while you digitize. I ’m told the device will be supplied coated in epoxy, a method meant to deter hardware pirates. The support software may also be supplied with John Yurek’s easy to crack but difficult to clone "fingerprint" (scratch on the disk) protection scheme.

Digisector 69 plugs into the expansion port or the Multipak Interface. It will probably work on a PBJ multiport as well. This unit will be provided with rather sophisticated software, with more support software to follow. One program enables it to render five levels of gray on the screen, while digitizing two frames per second (0.5 seconds per frame). This allows rather pleasing images of faces to be made. With a second support program it can produce up to 16 levels of gray on hard copy, but at a great price: the image takes eight seconds to scan. (Editor’s Note: Since hearing Dr. Goodman’s comments, the Microworks has improved the software so that this mode will scan in two seconds. Please consider this when reading the rest of this review.) I saw a few pictures of faces made using this eight second scan mode, and was stunned by their clarity. They were unquestionably the finest digitized pictures I’ve ever seen generated by the Color Computer; in some respects superior to certain digitizations I’ve seen on the Apple and IBM pc. Remember, though, to get such gray scale production an eight second exposure is needed!

In the two frame per second mode, pictures were moderately superior to those of faces done with the Grafx product, and roughly the same in quality as those produced with the Computize product below. Digisector 69 is the best choice for users who demand the highest possible number of gray levels. It is the best choice for transferring still photographic images with many gray levels into memory. Its two frame per second mode is acceptable for live sub-

jects, though a little sluggish. For the most part, a monitor to view the video signal while you are digitizing it needed to most effectively use this device. The current software support allows sophisticated adjustment of both vertical and horizontal contrast, and features a clever user interface. Further support software may later be released that will allow some degree of image processing and doing logical pixel operations on pictures (reverse, AND, XOR, etc.). The price of this digitizer is unlikely to drop in the foreseeable future. It will be supplied on a well laid-out printed circuit board in a black case. The pins will not be gold plated (they probably don’t need to be). Accompanying software will probably not be copy protected, in accordance with Micro Works long-standing policy. Micro Works may not make a schematic of its unit available for awhile, however. The unit uses a PIA and seven small·scale logic chips. An A to D resistor ladder under software control is the heart of its fine handling of gray levels.

The Computize digitizer is an improved version of the video digitizer designed by one of the authors of Graphicom. This unit is a true frame grabber, capable of digitizing a single video frame (1/30th of a second) at a time. Unfortunately, the digitized data must be transferred from an on-board RAM to the computer’s internal memory. This transfer takes

time. Therefore, while the device does digitize a single video frame at a time, it is capable of displaying only every sixth frame. This comes to five frames a second (0.2 seconds per frame). It is still by far the fastest of the three digitizers. When its controls are properly set, it can show up to five gray levels. Its ability to render faces is quite good . . . the equal

of the two frame per second Micro Works product, and slightly superior to the Grafx product.

The strongest point of the Computize digitizer is that it lets the user view a moving subject (such as a TV show) on the digitized screen in something like real time. For this reason it should be preferred by video tape addicts. Although it is the most expensive of the three video digitizers its great speed lets you use it effectively without having a monitor dedicated to viewing the video image. This may, for some applications, offset its high cost. This product is the most electronically complex of the three, using an 8K by 8 static RAM and 15 smaller ICs. Although I have not seen its final packaging, I have been assured that it is professionally made. The software interface for this product is through existing copies of Graphicom (version 1.2). All copies of Graphicom sold through all distributors had code for operating this video digitizer buried in them. The Computize product will be sold with instructions on how to activate this "undocumented" code.

This digitizer plugs into the expansion port and will work with the computer alone or with the Tandy Multipak. It will probably also work with the PBJ Multiport device. (end)