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The Complete Video Test System Dave Muse Version 1.0 March, 1994 INTRODUCTION The Complete Video Test System is a collection of twenty test patterns that you can use to evaluate, troubleshoot, or compare video equipment. Many of our tests are unique, and can be found nowhere else. This text will explain the tests in clear, non-technical language, and show you how to use your Complete Video Test System to make purchasing decisions, adjust your equipment for optimum performance, or just demonstrate the quality of the system you have. It is important to remember that, just as the strength of a chain is limited by its weakest link, the results of tests performed on your video system can only be as good as the poorest piece of equipment that the video signal must travel through. I will point out, as we go along, what types of problems with your system could result in low scores on the various tests. In addition to helping you evaluate your system, I will be telling you how to make adjustments to your TV or monitor to improve it. These adjustments are optional, as you may have to remove the back of your set to get some of them done. Many sets have an interlock to disconnect the power cord when the back is removed. You can defeat this by removing the end of the cord that is attached to the set's back and plugging it directly into the chassis (if you observe how the back goes onto the set, you will see how it connects the power cord to the chassis). THIS INTERLOCK IS DESIGNED INTO YOUR SET FOR A REASON! Working in back of your set with the power on can be dangerous! Be careful not to touch anything except the controls we are talking about, stay away from high-voltage areas (the high voltage cage and the picture tube), work with one hand only on the set (and keep the other one away from anything metal), and sit or stand on a dry, insulated surface while you work (like a cushion or carpet). Last and most important, don't sue me for your electrocution! I've just warned you, and you're on your own! CVTS is available as software that runs directly on an AMIGA computer system, or as a videotape playable on any of several types of VCRs. If you have the option, better results will be obtained by using CVTS directly from your AMIGA system rather than from tape. Most of the tests, however, will work just fine from tape with no compromise in function. USING YOUR SOFTWARE When using the software version of CVTS, remember that these tests are designed for NTSC television systems. This means you will need a genlock or NTSC encoder if one is not built into your system. The black-and-white video output on the AMIGA 500/2000 will work with a number of the tests (the ones that do not require color), and in fact I recommend using this output for as many tests as possible, if your genlock or encoder is not a high quality unit. The tests you will need color composite output for are: COLORBARS, COLOR PURITY, CHROMA RESOLUTION, CHROMA NOISE, COLOR CRAWL, and the MULTIPLE TEST. Black-and white output can be used for all the remaining tests, even when you are looking for the color symptoms mentioned and making the requested color adjustments. Users with monochrome only video output that do not wish to obtain an encoder can purchase a tape to run the color test patterns. If you want to try some of the CVTS tests on your RGB computer monitor, be my guest. All you'll prove is how incredibly superior RGB is to NTSC! The tests consist of pictures and animations displayable with any IFF picture/animation viewer. An easy way to tell whether a given test is designed for a TV or a VCR is to look at the icon. A drawing of a monitor is represented on some of the icons, and a video tape on others. A test that is intended for both will have a drawing of a monitor with a VCR on top. One test, the camera resolution chart, has a camera lens represented on its icon. This video camera test is the only one that needs to be printed before use. The easiest way to print it is to run Graphicdump (it came with your Workbench, in the utilities drawer) and display the test. It could also be loaded into a program like Deluxe Paint and printed from there. This test is specifically designed to work well regardless of the quality of the printer you have. GUARANTEE? The video tests that make up CVTS are designed for informal use by both video professionals and non-professionals alike. CVTS is not and cannot be designed to the same rigorous technical specifications as professional test equipment, and results from the former should not be given the same weight as results from the latter. I can't guarantee that you will make correct video purchasing decisions just because you own CVTS - as much as I hope and think you will. I can't guarantee that you won't damage yourself or your video equipment in the course of using CVTS (please be careful)! You'll have to assume the full risks for these things. So what do I guarantee? I want you to be happy with CVTS, so if you've purchased this package or anything else from me and you're not pleased with it, you may return it for a refund at any time. DISTRIBUTION NOTICE CVTS is copyrighted. This package is freely distributable, but not public domain. Distribute it as you wish - just keep everything together, this document included. Since this version of CVTS is shareware, you would (hopefully!) feel an obligation to contribute money to use it. Instead of a guilt-inducing diatribe from the author about $$, how about this: If you like this product and plan to use it, I hope you will consider purchasing a colorbar viewing filter, printed manual, videotape, or other product from me. They will enhance your copy of CVTS and make it more useful to you. Purchasing any product (see the included order form) will register you and put you on my mailing list for updates to CVTS. Yes, new tests and improvements to existing ones are in the works. I am also quite receptive to feedback. If you spot something wrong, don't curse me - write me a letter instead! THE TESTS Here is a brief description of each test and instructions for its use. COLOR BARS Everybody has seen the color bar test pattern before. It's a standard test signal, used throughout the television industry, for adjusting video signals. Professional television monitors frequently have a switch, labelled "blue only" , which is meant to be used with the color bars for precise adjustment. By using the blue viewing filter supplied with your kit, you can adjust your TV or monitor the same way professionals do. Here's how it works: (1) Find the control labelled "Color" on your set (it can also be called "Chroma" or "Color Level"). (2) Display the Color Bars on your monitor or TV, then look at the screen through your filter. CONTINUE TO USE YOUR VIEWER for steps two through five. The odd-numbered bars should appear blue, while the even-numbered ones are very dark, almost black. Observe that each blue bar has a smaller blue box just underneath it. While adjusting the COLOR control, compare the smaller boxes of the FIRST and LAST bars to the larger bars above them. When they are exactly the same brightness, the COLOR control is set correctly. (3) Find the control labelled "Tint" on your set (this control is sometimes called "Hue" or "Phase"). (4) While observing the two MIDDLE blue bars, adjust the TINT control so that the smaller boxes underneath them are the same brightness as the larger bars. (5) If the smaller boxes underneath the FIRST and LAST bars no longer match the bars above them, then go back to step one and repeat these adjustments. (6) Put down the blue viewer. Look for three small black bars in the bottom right quadrant of your screen. If you can't find them, turn your brightness up. When your TV is properly adjusted, the third (rightmost) of these boxes will be just barely visible - and the other two, invisible. Adjust your contrast and brightness controls until this happens. The reason you don't want to see the first black box is that it's actually "blacker" than black. Normal video material will never get blacker than the middle box, which is official television "black". Your TV or monitor is now perfectly adjusted to display color video. GREYSCALE Providing that you have just set up your monitor using the color bars, you should be able to distinguish all of the shades of black, grey, and white in this test pattern. If not, try adjusting your CONTRAST and BRIGHTNESS controls (some sets have a PICTURE control instead of BRIGHTNESS). Remember that the darkest shade of grey should be just barely visible apart from the black background. Observe, as well, whether inappropriate color tints come and go as these controls are rotated through their ranges. If some or all of the shades appear to be tinted with a color, it may be a sign that the "grey-scale tracking" or "color balance" of your set is out of adjustment. You can adjust this yourself, but you will need to look around for the controls in the back of your set. It may be necessary to remove the back cover to find them. What you need is a set of adjustments labelled "RED SCREEN","BLUE SCREEN", and "GREEN SCREEN". Alternatively, there may be adjustments called "RED DRIVE (the word GAIN may be used in place of DRIVE),"BLUE DRIVE", and "GREEN DRIVE". If BOTH sets of controls are present, remember that the SCREEN controls should be adjusted while observing the DARKER shades, or black, and the DRIVE controls adjusted while looking at LIGHT shades, or white. If you haven't done something like this before, be careful, especially if the back of the set is removed. Don't touch anything inside the set besides the controls you need (high voltages are present). Use a mirror so you can see the screen, and adjust the controls slowly. If turning a knob doesn't produce the effect you want, turn it back to where it was. A minor adjustment is probably all you need, so try to find the RIGHT knob to turn instead of turning ALL of them! Obviously, if your picture has a red cast, you will want to turn down the red control a little bit. If it has a yellow cast, though, you would need to add some blue. That's because of the way the three light primary colors mix to make white. Here's a quick guide: SINCE THE YOU NEED OR YOU NEED PICTURE LOOKS TOO: TO ADD: TO REMOVE: RED BLUE AND GREEN RED BLUE RED AND GREEN BLUE GREEN BLUE AND RED GREEN YELLOW BLUE RED AND GREEN CYAN (BLUISH GREEN) RED BLUE AND GREEN MAGENTA (REDDISH PURPLE) GREEN RED AND BLUE The above adjustments are for tinted shades of grey, white or black - usually affecting the entire screen at once - not a "splotch" of color that stays in one spot on the screen. If you have this symptom, or if a grey square appears colored BUT its identical partner on the other row is NOT colored or different colored, you have a COLOR PURITY problem. COLOR PURITY In this test, we are determining whether the electron guns are hitting the right phosphors on the face of the picture tube. What you are looking for on each of the colored screens is a small patch of "wrong" color - a green spot on the white screen, for example. Do not be alarmed at seeing "streaks" on the colored screens that come and go (if you are playing back this test from tape). These are caused by "noise" and are a normal part of the way tape reproduces colors. Look instead for a small-to-medium sized, fuzzy, stationary blotch of color, probably near an edge or corner of the screen. The test consists of several colored screens. Each screen should be a solid color from edge to edge. Is each shade of color consistent over the entire screen, or does it vary at any spot? Normally, color purity has been checked and set at the factory - its adjustment is located on the neck of the picture tube - and you should not need to readjust it. What a color purity problem usually means is that your picture tube has been subjected to a magnetic field, and may need to be de-magnetized, or degaussed. Most newer sets have a "degaussing coil" built in to take care of this automatically - yours could be malfunctioning or not be adequate to demagnetize your tube. See your local TV repair shop to have your tube degaussed - or borrow a degaussing coil to do it yourself. In addition to using this test, sometimes the GREY SCALE test works better for spotting subtle color purity problems. It is important to keep sources of magnetism away from your TV screen. Your picture tube can pick up magnetism from a telephone on top of the set (the bell generates magnetism when it rings), a floppy drive next to your monitor, a large loudspeaker closer than about two feet, or even a vacuum cleaner running too close to your TV. LINEARITY This test pattern will show you how accurately your monitor or TV set can display things like lines, boxes, and circles. The first thing you should look at is how well centered the picture seems to be. Can you see about the same amount of each of the four circles in the corners? Next, note how level the picture is. If it appears tilted, the YOKE (the large coil mounted on the neck of the picture tube) may have been incorrectly installed at the factory, or else has become loose and has twisted. Now, look at the large circle. Does it look perfectly round? If it's squashed or misshapen, that's a linearity problem. Observe that the lines appear straight and evenly spaced, too. The moving dashed lines will help you spot any sweep irregularities. Let your eye follow one of the dashes across the screen. Does it's length change as it moves? Does it appear to travel up and down a "hill" anywhere? If you'd like to improve the situation, look for two controls in the back of your set called VERT LINEARITY and VERT SIZE. Use your mirror to see the screen while you adjust them. You will find that these two controls interact with each other - that is, they both affect the vertical height of the picture - so you will need to adjust both controls simultaneously. Use the VERTICAL LINEARITY adjustment to make the large circle look as round as possible while turning the VERTICAL SIZE knob to keep the picture the right height. Some older TV sets and monitors have a PINCUSHION control. Its purpose is to compensate for the curved screens of some older picture tubes by "pushing in" the scan lines at the top of the screen. If the lines at the top or bottom of your screen ONLY look bowed or wavy, look for a PINCUSHION control in back of your set. CONVERGENCE Since it takes a mixture of the three primary colors to create all the colors we know, it probably comes as no surprise to know that there are three "electron guns" inside your picture tube, one for each of the primaries. The tricky part of all this is getting the beams from those three guns to strike the screen in exactly the right places. If they don't line up just right, colored fringes will appear around objects on the screen. Display the dot screen and look right in the center of the screen. Do you see white dots or multi-colored dots? Most sets are pretty good at getting the dots white in the middle of the screen. Now look in one of the corners. If you look closely at one of the dots, it will probably appear to be colored around the edges, or it may have split completely into two or three colored dots. If the convergence of your set is particularly bad (that is, the dots don't appear white even at a distance) you may wish to adjust the convergence of your set. There are typically two sets of convergence adjustments, called STATIC and DYNAMIC. The STATIC adjustments are little tabs connected to magnets on the neck of the picture tube, and do not usually need adjustment outside of the factory. They are used to get the center of the screen lined up. The DYNAMIC controls are needed to get the screen converged around the edges, and may need to be touched up every few years. These controls may or may not be clearly marked, so look carefully for a small group of electronic controls, possibly on a circuit board of their own, near the back of the set or even on the picture tube neck. We're talking screwdriver type adjustments here, so find a small insulated screwdriver and/or coil adjuster to use. I have no ideal strategy for adjusting these, as every TV or monitor is a little bit different, and the convergence adjustments can be difficult. If you would like to experiment, then use your mirror to see the screen, proceed carefully, and turn each control slowly to see what effect it has on the picture. If It doesn't do what you want, turn it back to where it was! FOCUS I have provided a black-on-white dot screen for checking and adjusting FOCUS, but the same dot screen used in the convergence test above is also useful - try them both. Do the dots appear as tiny, well-defined little rectangles, or as fuzzy round blobs? Many sets have a FOCUS control which is accessible without removing the back. If you have such a control, try adjusting it while observing the dot screen. You want to make the dots look as small and well-defined as possible. If you find it impossible to get both the center of the screen and the edges to look sharp at the same time, a compromise setting of the control may be necessary. Picture brightness often has an effect on image sharpness as well. To check this, see whether both of the dot screens play with equal focus - and try turning the BRIGHTNESS control up and down as well. A well-designed and built set will not lose very much focus as the brightness control is turned up, but some sets lose quite a bit of their image quality. If yours is in this category, you may have to choose between a bright picture or a sharp one! BLOOM Blooming refers to the tendency of the size of the RASTER (the tv image projected on your picture tube) to increase with brightness. When you run the BLOOM test, you will see a cross made of two graduated lines, alternately black on a white background, then white on black. To see how much size variation your TV has, you will need a tape measure. Measure from point A to B on the black screen, then again on the white screen. Divide the larger number by the smaller. Do the same thing again, measuring from C to D this time. A good score on this test will be as close to 1.00 as possible. WINDOW The WINDOW test, despite its simple appearance, presents a challenge to your video system. Turn your BRIGHTNESS and CONTRAST (or PICTURE) control up and down with the window test displayed and look for problems. Some things to look out for: - Are all the sides of the large white square straight and even, or are there waves and kinks? - Are there streaks or smears running horizontally across the picture? - Is the square white, or tinted with a color? - Do you see "ghost" images of the sides of the square (possibly multiple ghosts, especially with the brightness turned up -- and with the peaking or sharpness control turned up). - Are the square edges sharp or blurry? Good results on this test require a solid, flat response from the electronics in all your video equipment. A problem could be caused by several things. If there is a peaking or sharpness control on your TV or VCR, make certain it isn't turned up too high. If you are using a monitor rather than a TV, make sure that it is terminated properly. Check for a termination switch on your monitor. If video "loops through" your monitor on it's way to another piece of video equipment, the last video connection in the chain needs to be terminated. CENTERING A quick look at the concentric boxes on your screen should tell you how well centered your monitor is. Can you read the same letter on both the right and left sides of the screen? Follow the outermost box all the way around the screen to judge your top/bottom centering. You can quickly gauge the amount of overscan your set has, as well. The outermost box is labelled "A". Which letter can you read at the edge of your screen? For a more precise overscan measurement, see the next test. OVERSCAN It's almost impossible to frame a picture without covering a small part of it behind the frame. The same thing happens with the video image displayed on your set. The image is purposely made just a little larger than your screen, so that you won't see the edges. While a small amount of lost image, called overscan, is acceptable, a good monitor or TV will crop very little off the sides of your picture. To measure overscan in your set, run the test until the expanding box begins to leave the screen. If you pause the tape (or stop the animation, if playing from computer), you will be able to read the percentage of overscan, or lost image in your monitor or TV. A reading in single digits is acceptable. This is a good time to check your centering, as well. If all four sides of the box seem to be leaving the screen at the same time, then your picture is centered perfectly. If you would like to adjust the overscan or centering of your set, you may be out of luck. Many TVs or monitors don't have adjustments for horizontal size or centering. Check for yourself and see. Vertical size and centering controls are more common - but you'll want to be careful about changing the vertical size of the picture if you can't change the horizontal - squashed or stretched pictures could result. If your monitor does have a full complement of controls (horizontal size, vertical size, horizontal centering, vertical centering, and vertical linearity), then call up the LINEARITY test screen and use the centering controls first, then the size controls. Don't forget that you might need to adjust the vertical linearity control as well, to keep the circles as round as possible. Once you get everything right, call up the CENTERING test to fine-tune the positioning controls. Suppose you've adjusted all the overscan out of your set, so that all the edges of the raster are visible on the screen, and you still can't get to zero on the overscan test? This problem has to do with the BLANKING in your set. Blanking refers to the period of time the scanning beam is turned off, so that it can be positioned for the next line or frame of video. In many sets, this BLANKING INTERVAL is longer than absolutely necessary, and so may contribute to the overscan in your set. HORIZONTAL RESOLUTION This is an important test, and it applies to both your VCR and TV or monitor. RESOLUTION means sharpness, and what we're measuring is exactly how sharp an image your video system can display. There are separate tests for HORIZONTAL and VERTICAL resolution, as well as one for CHROMA, or color resolution. We need all these separate tests because different technical characteristics are responsible for resolution in each case. HORIZONTAL RESOLUTION is typically measured as "Bandwidth" by engineers. The concept of "Lines" is more easily grasped by consumers, however, so camcorders, VCRs and monitors usually have their resolution expressed in lines, that is, the number of vertical lines that can be fit on the screen while still being able to distinguish them. This measurement is sometimes made in more than one way, so I have included three sets of numbers on the test. The top set of numbers represent the traditional way of measuring LINES OF RESOLUTION, which is the number of black and white lines that would fit on your screen IF IT WERE SQUARE. Since it is not square, but rather rectangular, the bottom set of numbers indicates the number of lines that will ACTUALLY fit on your screen. From time to time, measurements made this way will be quoted in specifications - which is hardly fair if everyone else uses the traditional measurement. The middle set of numbers are for BANDWIDTH, expressed in megahertz. This method of measuring resolution is the most popular with engineers. The test is for the luminance part of the picture (the black-and-white portion of the TV signal) SO TURN YOUR COLOR CONTROL ALL THE WAY DOWN. How far to the right can you look before the lines blur together? The highest number you can get while still being able to see individual lines is your horizontal resolution. If the lines are dim, but you can still see them, it still counts (this means that your response is "falling off" at these frequencies). Increase your contrast control and back off the brightness a little bit to improve your view of the lines. A good VHS VCR will only score in the low 200s on this test. Some formats (like S-VHS) are capable of scores of up to 400 lines, but you'll need a good monitor to see it. Most TV sets are only good for 250 lines or so. If you have some good quality equipment, you might be curious why you can see the 315 line grid, but not the 275! The reason is complicated, but it has to do with the fact that the part of the TV signal that carries the color information has a frequency very close to that of the 275 line grid. This is why, if you turn up your color control now, you will see crawling colors all over this part of the screen. Your TV is mistaking this grid for color information! If your TV has a "comb filter", this grid may be a little clearer. If your TV or monitor has a special S-VIDEO connection to your VCR, it is much more likely to be visible. This is why a special monitor is recommended for S-VHS, HI-8 and similar formats. If you are running CVTS from the AMIGA software, you may notice a quality difference on this test between the color composite output of your genlock or encoder, and the monochrome output (AMIGA 500/2000) which contains no color subcarrier (this will cause it to look better). VERTICAL RESOLUTION This is a little tricky to explain, so bear with me. All TV equipment has exactly the same vertical resolution. This is necessarily so because this parameter is a part of the standard that our TV system (the north american TV standard is called NTSC) is based on. So what is the standard vertical resolution? Well, this is the tricky part. There are 525 scan lines making up one frame of video. Some of these aren't used for video, so there are a little less than 500 left. This would imply a vertical resolution of almost 500 lines. The catch is that it takes the electron beams in your picture tube two passes to paint all these lines on the screen. First the odd-numbered lines are drawn, then the even-numbered ones. This even-odd business (called INTERLACING) makes it very hard to distinguish lines right next to each other, because very thin lines will appear to flicker like crazy! If you look very closely at the VERTICAL RESOLUTION test pattern, you probably can see all the lines in all the grids, all the way up to 500. However, it would give you a headache to count them. This is why the APPARENT vertical resolution of NTSC television is usually quoted at 300 or so. Lots of flicker means your equipment is working perfectly. Little flicker, or unusual difficulty seeing the lines could mean that your TV is not interlacing properly, or your VCR is not playing back both "fields" of the TV picture (mis-tracking, or a dirty or damaged head are some possible causes). When using this test to compare TVs, record the highest number of lines you can EASILY see (the APPARENT vertical resolution). INTERLACE If you think about the the process of INTERLACING, where the lines of the second field of video are drawn in between the lines of the first video field, you might start to wonder if anything could go wrong. The answer is yes, things can go wrong, and lines of video can be scanned in wrong places. In particular, if there are brightness variations from field to field, the raster can expand or contract - putting the lines in the wrong place. The result - fuzzy video. When you run the INTERLACE test, you'll see a screen that flickers like crazy. Start with the brightness and contrast on your set turned down as far as possible, while still being able to see the video. Superimposed on this flickering pattern are the words "How well can you read this?", repeated in five places on the screen. You will notice that this message is white, with a black drop shadow that just barely falls off to the lower right. Now turn up the BRIGHTNESS and CONTRAST (or PICTURE) controls to normal levels, and observe both the legibility of the five messages, and the positions of the black drop shadows. Ideally, all five messages should look the same, with the drop shadows in the same places - just barely falling off to the lower right. Otherwise, your monitor has some trouble interlacing under the difficult circumstances presented by this test. CHROMA RESOLUTION This test is just like the HORIZONTAL RESOLUTION test except that we are looking at the resolution in the color portion of the TV signal. Make sure that the CHROMA (or COLOR) knob on your TV or monitor is turned UP to it's normal level. To score your equipment, find the closest together set of bars that you can make out, and read its corresponding number. Don't expect a high score on this test, unless you have professional equipment. This is a good test to use when trying out VCRs and monitors, as there can often be substantial differences. To test a monitor, I recommend playing the test direct from computer, as your monitor probably has better resolution than your VCR. Why is your chroma resolution so much poorer than your luminance resolution? The answer has a lot to do with the designers of our NTSC TV system (and PAL, as well, a related TV system). They knew, from vision research, that humans see much more detail in luminance than they do in color. This is why there is much more bandwidth allocated for brightness information than for color in the TV specifications. Unfortunately, your TV or VCR will truncate still more of this chroma information. LUMINANCE NOISE NOISE is what you're looking at when you watch a TV station that doesn't "come in" very well. Most of us are used to calling this "snow" because that's what it looks like - a snowstorm in front of the TV show we want to watch. All TV signals contain noise, but usually not in objectionable amounts. To measure noise objectively, professional test equipment is required. However, we have developed tests that work quite well for comparative measurements of both luma and chroma noise. Two different tests are needed because the video signal has two parts: one carries the brightness, or luminance information, and the other carries the color, or chrominance information. These tests are best used for subjective, comparative purposes and will not produce meaningful numbers for professional use! To use the LUMINANCE NOISE test, first turn the CHROMA (or COLOR) knob on your set all the way down. If your VCR or TV has a sharpness or peaking control, set it at the middle position. If you have digital noise reduction, or a "detail enhancer" on your VCR, turn these gadgets off (they will hurt your score, not help). Run the test. You will see a noise bar, with a significant amount of noise on the right end. Now, take note of the amount of noise visible on the left side of the bar. Next, look slowly across to the right until you find the point where the noise seems to be just noticeably worse. The number above this spot is your score. CHROMA NOISE The CHROMA NOISE test is just like the LUMINANCE NOISE test above, except that you should now turn the CHROMA (or COLOR) knob on your TV back up to its normal position. Look across the red bar from left to right until you find the spot where the noise in the color seems to begin worsening. Read your score just above this spot. COLOR CRAWL The color TV signal, as we have mentioned before, is a mixture of luminance (brightness) information and chrominance (color) information. An unfortunate side-effect of mixing these two signals is that they can interfere with each other. At the places on the screen where this is happening, an artifact known as COLOR CRAWL or DOT CRAWL appears. Run the COLOR CRAWL test pattern, and look at the left and right sides of the various colored boxes. You might see a pattern of dots, "crawling" up the screen just at the borders where colors change, or, alternatively, it may look more like an ill-defined crosshatch pattern. If you see this effect on the left and right sides of the colored boxes, and nowhere else, your set uses the "trap filter" method of separating the chrominance and luminance. If you see little-to-no effect on the left/right sides, but some chroma crawl on the tops/bottoms of the colored boxes, your set almost certainly uses a "comb filter", a vastly better method of separating the signals. If you are watching on a set connected by an S-Video connector to an S-VHS or HI-8 deck, you should be treated to a display with NO chroma crawl at all. Now you know why you spent all that money on your video system! You could find, as I did, that playing your test tape on different VCRs, even through the same cheap TV set, can produce widely differing results on this test - owing to the quality of the VCR's encoding (the process of recreating the TV signal from tape). Don't be dismayed to discover that an expensive monitor has more chroma crawl than a cheap one - this is probably a trade-off that comes with the higher resolution of the better monitor. CAMERA RESOLUTION If you have a video camera, you can perform horizontal and vertical resolution tests on it using this chart. First, you'll need to have it printed. To print from Workbench, open the printer graphics section of preferences and set your ASPECT to VERTICAL and SHADE to BLACK AND WHITE. Now run GRAPHICDUMP (this program is in the utilities drawer of your workbench) and immediately display the CAMERA RESOLUTION chart using the IFF viewer of your choice. Alternatively, you may print from a program such as Deluxe Paint. When your printer is done, compare the finished chart to the one on the screen. It doesn't need to look perfect - as long as all the lines seem to be present, it's fine. To measure the horizontal resolution of your camera, set your camera on a tripod and tack the chart on the wall as straight and level as you can. Get the camera as close and perfectly centered to the chart as you can, while still being able to focus. Then, zoom all the way in on the exact center of the pattern and focus there. Now, slowly zoom out, watching the pattern of lines. When they have blurred together so that you can no longer make out individual lines, stop zooming out. Look to either edge of the frame. The number you see there is your resolution. Measuring vertical resolution is simply a matter of turning the chart sideways, and repeating the above instructions. It's possible that your camera won't be able to focus close enough to the chart. One solution is to print the chart larger, if possible. Otherwise, use the MACRO setting on your camera lens to focus closer. Since this will preclude the use of the zoom lens, simply focus on the resolution brackets one at a time, until you find your camera's limit. DROPOUTS This test is designed for comparing video tapes. If you were to try to choose the best brand of video tape by running the CVTS tests on them (the appropriate tests are: LUMINANCE NOISE, CHROMA NOISE, CHROMINANCE RESOLUTION, and LUMINANCE RESOLUTION), it isn't likely that you'll spot any differences at all. Video tape is made to such high specifications that any performance differences are going to be extremely minor - unless you're comparing ultra-cheap made in China dollar-store special tape to extra-high-grade super-VHS stock. The one area where you can often find substantial differences between tapes is in DROPOUT COUNT. A dropout is a small area of tape where a signal won't record. This could be caused by a speck of dust, a small wrinkle, or an uneven distribution of oxide. A dropout, on playback, looks like a small - or occasionally large - horizontal white streak on the picture. What this extremely simple test does is give you a chance to count dropouts. To use it, record it on the tape of your choice in two spots - at the very beginning of the tape, and again in the middle of the same tape. Next, play back the sections of tape you have just recorded, and get ready to count the number of white streaks you see. The test consists of a countdown, followed by exactly one minute of black. When you see the black, begin counting dropouts. When the screen says stop, write down the number of dropouts you saw. Typically, there will be many more dropouts at the beginning of the tape than in the middle. To get the best idea of the quality of the brand you are testing, test several of their tapes bought at different times, including some that have been used for a year or two. If you can't spot ANY dropouts at all, your VCR may have a DROPOUT COMPENSATOR, a circuit that "fills in" dropouts so you won't see them. Use a different VCR for your tape tests. THE MULTIPLE TEST PATTERN You will recognize elements of many of the tests discussed above in this test. When using this pattern to evaluate a TV set or monitor, first set the COLOR and TINT controls using the color bars, then use the grey scale to set the BRIGHTNESS (or PICTURE control) and CONTRAST. Now, look at the grey scale... are the shades of grey accurate, or tinted with a color? Look at the dots around the edges of the picture... how sharp are they? Does the sharpness, color tint, or picture size change when you turn the BRIGHTNESS or PICTURE control up and down? How many dots look mis-converged? Examine the transitions between colors on the color bars for dot crawl. Look at the large circle... is it round, or is it oval or misshapen? Does the picture appear level, and centered? How much overscan does this set have (count the number of dot rows you see - there are two columns on each side and four rows on the top and bottom). You can use the two resolution tests if you like, but to be fair, if you can't run the test directly from your computer, you'll have to use a SUPER-VHS or HI-8 version of this tape to test monitors. A plain old VHS machine will always have poorer resolution than a TV or monitor. I don't recommend using the noise tests at all when comparing TVs, for the same reason. Any non-professional format VCR will create more noise than a typical TV set. If the score on one of these tests looks way out of line, though, the TV could have a problem. NOTES ON USING THE TESTS When comparing VCRs, the important tests are HORIZONTAL RESOLUTION, CHROMA RESOLUTION, LUMINANCE NOISE, CHROMA NOISE, WINDOW, and COLOR CRAWL. Using the same good-quality TV or monitor each time will give you the fairest result. When comparing TVs or monitors, all the tests are valid, though the NOISE tests have been designed principally for VCRs - a typical TV by itself (running the tests directly from computer) will score at the top of the scale. Don't be led to believe that just because you've set your monitor up to the CVTS colorbars, all TV programming will now appear in perfectly adjusted color. This may turn out to be the case, by the way, but if it's not, it's because you don't have the colorbars associated with each and every tape or TV show, as in the professional video production world. Some programmers (your local cable access channel, for example) may be lazy about implementing good technical standards. Having your personal equipment properly set up does nothing to assure that the signal entering it has been processed with care. HINTS ON SHOPPING FOR A TV You know what it's like. Fifty-seven television sets, all displaying the same TV show. Should you buy the set with the picture that looks best to your eyes? Believe it or not, sometimes the set with the worst-looking picture is the best one. If the program displayed on all those TV sets contains NOISE (a VHS movie or a snowy cable channel, for instance), then the set with the best resolution will be displaying the most noise! There's a relationship between noise and sharpness - they go together. The situation is analogous to playing a noisy old 78 RPM record through a set of expensive stereo speakers. This record might sound better played through an old, low-fidelity speaker that doesn't reproduce every scratch and pop with annoying clarity. You wouldn't use an old record like this to buy a stereo system, would you? Don't forget that most sets have a SHARPNESS control. You can turn down the sharpness when watching those fuzzy VHS tapes, to get rid of the noise. If your set has the extra resolution, however, you'll really appreciate it on high-quality noise-free program material. If you can record the CVTS tests on tape and take it along, you will find out a lot about the set you want to buy (you will awe the sales staff, too!). You may want to narrow down the field a bit first, though, so here are some ways to analyze the sets quickly. Watch the picture as the program fades to and from black between commercials. Does it seem to change size, focus or color? (Bad signs.) Compare the pictures of several adjacent TVs to find and eliminate the ones with too much overscan. Look for dot crawl on the sharp edges of strongly colored objects. If you see it on the TOP and BOTTOM edges more than on the SIDE edges, this is a sign of a COMB FILTER (this is good). Check for straight, level lines and round circles whenever these things appear on the screen. Next, look around the edges of sharp bright objects (white lettering, for example) whenever you can. Are these edges clean, or are there "wrinkles", "ghosts", double edges or unnatural looking white borders? Look in the corners of the screen for colored fringes around objects - a sign of poor convergence. Finally, try not to overlook a set that may have been simply misadjusted by a salesperson. You may even want to help him/her out by properly setting it up. ORDER FORM The following items are available from Dave Muse Video. You may print this form and simply circle what you want - or write on a separate sheet of paper. I am working on a list of benchmarks for various pieces of video equipment - I will include this with every order. COLORBARS VIEWING FILTER Used in conjunction with the colorbars test signal for adjusting monitors and TVs. - $5.00 COMPLETE VIDEO TEST SYSTEM - TAPE, DISKS AND MANUAL The CVTS tests recorded on tape and ready to use for evaluating monitors, TVs, and VCRs. Includes printed manual, colorbars viewing filter, camera resolution chart and the latest Amiga computer version on disk as well. Additional help screens explaining each test are recorded on the tape. VHS - $28.00 SUPER VHS - $34.00 3/4" - $36.00 Other formats - Write first COMPLETE VIDEO TEST SYSTEM - DISKS AND MANUAL The latest version of CVTS on disk plus a printed manual, camera resolution chart and colorbars viewing filter. The manual contains additional instructions and diagrams to make using the tests even easier. - $16.00 Please circle the prices of the items you want above, and total here: $________ Shipping: Add $2.00 per product ordered (except for the viewing filter - no addl. charge.)$________ MI residents have to include sales tax: $________ Add everything up here: $________ Mail this and any other correspondence to: Dave Muse 22443 Leewright Southfield, MI 48034