FAQ: The Attractions of Video Frame Grabbing
- How Bob's Rock Shop Got Started -

If you are already familiar with NTSC video and frame grabbers in general you'll probably want to skip ahead to the next section detailing hardware and software particulars.

While the Shop's other specimen image contributors are using a variety of photographic and scanning equipment and techniques, all of the images of specimens from Bob's mineral collection were generated using relatively inexpensive hardware and software to capture and process still images from NTSC video. The video frame capture techniques and hardware used offer several attractions besides low cost and can be applied to acquire image files of virtually any subject of interest to you.

NTSC (National Television System Committee) video sources abound. Unless you live in Europe or some other place where the video standard is PAL, every time you change channels on your TV, cable or satellite tuner you are switching among NTSC video sources. Your collection of video tapes and your VCR are an NTSC video source library. And if you own or have access to the use of a video camera or camcorder there is at your disposal an NTSC video source that can be used to acquire almost any image you might want.

The mind-numbing quantity and diversity of NTSC video images both archived and pouring anew at us every day present inherent attractions for documentary as well as creative work. The NTSC video signal standards were established in 1953. A lot of NTSC video has been taped since then. You've probably taped a little yourself. There's no shortage of raw material available as NTSC video.

The nature of the NTSC video signal itself (hereafter referred to as composite video or just video) offers certain attractions as an image source. Composite video is generated and transmitted in frames which are refreshed 30 times per second. These video frames are analogous to the image frames on old style photographic movie film. Each composite video signal frame can be converted to an image file with a hardware device that is generically known as a frame grabber. Combine your TV, VCR and/or camcorder with your personal computer, a low-end ($100-$200) frame grabber, your favorite paint programs and some graphics utilities, and you've got your very own digital graphics studio with which to work and play. You probably own most of this stuff already. A frame grabber ties it all together.

A significant advantage of video frame grabbing over conventional photographic methods of image acquisition is realized by eliminating the time and money spent in developing film, printing and then scanning. With video frame grabbing techniques the image file is generated directly from the video source. In studio environments, this allows for making very quick adjustments to video camera position, focus, lighting, subject orientation, background, etc. if the captured image indicates the need for such corrections. If you shoot video tape "in the field" that you later decide needs to be redone, you'll still have to go back out and shoot again. At least video tape, unlike film, is reusable.

Video tape offers an extremely cheap medium for storing images. If a single frame of composite video is captured as an uncompressed 640x480x24-bit color image file it will occupy 900,000 bytes or so. Viewed this way, a 90 minute VHS video tape stores the equivalent of 900,000 bytes/frame x 30 frames/sec x 60 sec/minute x 90 minutes = 146 gigabytes of images on about $3 worth of medium. Of course, you can't access a video image with a VCR and a frame grabber as fast as you can on your new $250, 2.5 gigabyte hard drive. But then again, you'd have to hook up about 400 of those 2.5 gigabyte drives to store the terabyte of images you can store and retrieve with your VCR or camcorder, an inexpensive frame grabber and a handful of video tapes.

Making the Shop's First Mineral Specimen Images: Equipment, Software and Techniques

Bob's Rock Shop was spawned through an experiment with a Captivator frame grabber one Sunday afternoon in February 1995. That experiment has run rather late into the night...

The Camera

The video output from a now antique Sony CCD-TR5 NTSC 8mm camcorder was used as a signal source to feed the frame grabber. A test subject was needed and I just happened to have a rock or two within handy reach... When I saw those first specimen images on the monitor something clicked (or was that snapped?) and Bob's Rock Shop was born! A tripod for the camcorder quickly proved to be a useful accessory. An indispensable feature of this camcorder for shooting rocks was it's macro lens, which provided the ability to shoot very close-up to the subject. The image's depth-of-field was very shallow in macro mode and the small black and white LCD viewfinder of this camera made precise focusing without the use of a monitor somewhat challenging.

Before an integrated studio was set up, several of the specimens were video taped with the camcorder in one location and frame grabbed off the tape later at a different location. While more or less passable, the images that were grabbed off tape were noticeably inferior to those grabbed off the live video signal from the camcorder.

The Shop has since upgraded to a Canon ES3000 Hi-8mm camcorder, which boasts a color viewfinder and a very nice 20:1 optical zoom lens that will focus a subject that's practically in contact with the lens, among many other advanced features. The Hi-8 format provides higher resolution than standard 8mm camcorders, and frame grabs generated from Hi-8 tape are much more viable. Still, even with Hi-8, the best frame grabbed images are acquired under studio conditions with live video from the camera feeding the grabber directly.

The Studio

A simple but effective studio for doing the mineral specimen shots was assembled on a couple of adjacent card tables. A piece of black poster board was employed as a seamless background. A piece of black spandex material was draped over it and used as background for several of the images. The most challenging problem with an indoor studio is the lighting. Getting enough light isn't the problem; getting the right color light is.

Reproducing the effect of sunlight indoors on the cheap is not easy. Tungsten sources are too yellow, cool white fluorescents are too cool, grow lights are too red. Mixing different colored sources in various combinations can yield satisfactory results. Wide spectrum fluorescent bulbs are available but are not a panacea. Direct sunlight streaming through an unobstructed window can be nice to work with if you can arrange it. Clouds are great diffusers. Of course you can always shoot outside in the sunlight, but depending on your situation this may require you to record the shot and frame grab off tape rather than the undegraded live signal from the video camera. Special white light sources for studio photography are available from photographic equipment suppliers, but they don't exactly give these lights away.

A "spare" table-top color TV makes a handy video monitor to check and adjust the lighting and the camera focus if your video camera's built in monitor is lacking. A "spare" VCR can be handy to have around the studio too.

The Captivator Frame Grabber

The frame grabber used to capture the first generation of specimen images of rocks in Bob's collection was a now discontinued 16-bit half size ISA card called the Captivator that was manufactured by Videologic. VideoLogic recommended an IBM or fully compatible E/ISA standard PC with a 33 MHz 386, 4 Mb ram and a 100 MB hard drive running Windows 3.1 as the minimum platform to support this card. VideoLogic has since discontinued the Captivator, citing unavailability of electronic parts discontinued by manufacturer as the reason. They do not have an direct replacement at a low-end price point. You may still be able to find this grabber in stock at some catalogers and retailers. It's a shame to see this board disappear; at $100 it was a good value and an inexpensive introduction to frame grabbing and computer video.

The Captivator card came bundled with Microsoft Video for Windows and VideoLogic Videosnap software. It can frame grab 8, 16 or 24-bit RGB images from Pal as well as NTSC video sources with a maximum resolution of 640x480 pixels. It outputs image files in DIB and BMP formats. AVI format movies can also be made with this package. If you want to play with movies, the faster your machine is, the better.

I've used this frame grabber with a 33 MHZ 386 SX as well as a 100 MHZ 486 DX4 and it functioned properly in both machines. Installation of the card and software was straight-forward and well documented. Mine cost just under $100. VideoLogic still offers a high end video and still capture board, the Captivator PCI. Further information regarding it is available at thier web site, VideoLogic Online.

The Snappy Frame Grabber

If you're shopping for an inexpensive frame grabber you should consider the Snappy Video Snapshot from Play Incorporated. The minimum required computer platform is similar to the Captivator card. The Snappy can provide up to an impressive 1500x1125 maximum capture pixel resolution with 24-bit color. In my experience, the image quality suffers some in this high resolution mode, but that it can do this at all is somewhat of a breakthrough at its price point. It plugs into your computer's parallel printer port, eliminating the need for an open slot on your motherboard along with the potential hassles of getting a new board to coexist with everything else on your bus. It's what you might call "Plug and Play". :)

I've used the Snappy with a 486 DX4 and a plain vanilla parallel port on an EISA controller card, and several other machines up to a 166 MHZ Pentium Pro with integrated on-board ports, and have had no problems with the Snappy hardware or the software on any of them. It comes bundled with Snappy Video Snap Shot software, which provides the fundamental GUI to the frame grabber as well as a number of luminance, color and filter controls. Also bundled with my Snappy was the Snappy edition of Fauve Software's Fauve Matisse, which provides more advanced image editing tools, and Gryphon Software's Morph.

The Snappy software outputs image files in BMP, PCX, TIFF, TGA and JPEG formats. This grabber doesn't do movies. I paid just under $200 for mine, but I've since seen this grabber advertised for less through catalogs like Tiger Software. The Snappy has received numerous favorable product reviews in various computer magazines. Visit Play Inc.'s Snappy Home Page for further information on this grabber, including some downloadable demo images. I like my Snappy very much. It does a nice job of grabbing video "stills" and it's easy to install and use.

When I can spare the time, I'd like to spend an entire weekend or two redoing all my early rock collection images with the Canon Hi-8 camcorder and Snappy frame grabber. While I tend to wax nostalgic over my early images, the Canon Hi-8/Snappy combination is capable of markedly superior results over the camcorder and grabber I got started with. I've also learned a thing or two about lighting techniques since initially imaging my collection, and have come to appreciate that control and application of light is even more important to creating good images than having the latest and greatest gizmotrons. Professional photographers have known and preached that for years. Of course, I've also added a few more rocks to my collection that need imaging since I started frame grabbing...

Shareware Software

The BMP format images output by the Captivator's Videosnap software were further processed with a shareware bitmap editor, Paint Shop Pro 3.0 from Jasc, Inc.. This software requires a minimum platform of a 386 with 4 MB ram, VGA, a hard drive and Windows 3.1. Paint Shop Pro 3.0 directly supports 26 different raster image formats and 9 meta and vector image formats. It is capable of reading additional formats with the installation of external import filters. Paint Shop Pro incorporates many useful functions for working with image files including an image file browser/manager, a screen capture utility, pixel level editing with an array of drawing, paint and select tools, color depth and palette management functions. It incorporates a number of standard and special effects filters and supports both user-defined filters and Adobe-compatible plugins.

Paint Shop Pro was used for cropping, resizing, and adding borders and text to the BMP format mineral specimen images. Most of the images were also processed with several of the image contrast and sharpness filters. After a satisfactory amount of puttering had been performed on each image it was converted with Paint Shop Pro to JPEG format. A shareware version of Paint Shop Pro is available for downloading from the JASC Inc. Home Page. I paid $69 plus shipping for a registered copy of Paint Shop Pro 3.0 and a manual. I subsequently particpated as a beta tester for Paint Shop Pro 4.0 and was provided with a gratis copy when it was released.

Another nice shareware program that's available for puttering with image files and converting between formats is Alchemy Mindworks Inc.'s Graphic Workshop for Windows. This one cost $40 plus shipping to register.

The comp.graphics.* Usenet newsgroups are a rich source for information on image files and software tools for manipulating them. If you haven't already explored them, their FAQs provide an excellent introduction to image files and related topics.


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bkeller@rockhounds.com 5/23/97