What determines the maximum horizontal and vertical resolution of a CRT tube? - Page 1
Forum section: electronics / projects

author: Fusion916
author_rank: Regular Contributor
timestamp: February 10, 2017, 09:50:32 pm
content: I'm trying to learn more and more about CRT tech (both theory, design, repair, etc) and one thing I want to understand is what determines the maximum resolution of the tube itself, meaning with the entire chassis removed to remove any concern about video bandwidth, horizontal drive, etc. Just the tube, yoke, and the electron guns.So with that said, in the tube design itself. What about the physical construction determines the resolution? Lets take standard NTSC tvs for example. I know that the spec is 525 scanlines, but only 480 of them are viewable. Does that mean the physical construction of the tube has 480 lines of resolution? Also, what is the determining factor of the horizontal resolution? And how do TV lines relate to this.One more thing is displaying as interlaced vs progressive. Again, removing the chassis part of it, is there anything inherint in the CRT tube itself that prevents progressive display vs interlace display? All SD CRTs have the 480 total scanlines, so what in the tube itself prevents progressive display? Is the design of the yoke too slow to scan 480 lines every 1/60th of a second? If that is the case, in theory shouldn't it be able to do 480 lines at 30fps?

author: helius
author_rank: Super Contributor
timestamp: February 10, 2017, 10:36:00 pm
content: In general, a CRT does not have a "resolution" per se. It's an analog device with variable acceleration voltage and beam current, which affect the size of the bright spot. Since you can control the X-Y deflection in any way you want, to draw curves of any shape, there is no such thing as a "resolution" in the tube itself.Most color tubes work on a parallel tricolor system with three electron guns, and a shadow mask or aperture grille that lets electrons from each gun strike spots of their respective color phosphor. The spots have a definite pitch (measured horizontally, or at an angle), and those are a lower limit on the number of distinguishable pixels. But the CRT can certainly be scanned at a higher resolution; it will act as a low-pass filter.On monochrome tubes (or tubes with sequential or penetration-based color), there are no spots, as the phosphor is a continuous coating. But the tube's electron beam must be focused to stay in a small spot, and it can't be both infinitely sharp and bright. More beam current makes the spot "bloom" and so increasing brightness leads to decreased acutance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 10, 2017, 11:06:39 pm
content: Quote from: helius on February 10, 2017, 10:36:00 pmTo refine the point:1. Without any grille, a monochrome display is just phosphors, in which case the mentioned limits apply: beam focus, scattering, and the beam's focal plane. These, in turn, are largely set by the CRT design, and by physical law. 2nd anode voltage is the most important figure in beam sharpness; but you can't simply crank up the voltage on a poorly made tube (which will probably flash over before you get very high!). Sharp focus is best achieved by simply finding a well-made tube.2. The grille doesn't just act as a low-pass filter, though: it's a sampling aperture. That means any high frequency information is downconverted -- giving aliasing, better known as Moire patterns!If you display a checkerboard pattern on a Trinitron CRT, you see a Moire pattern, which gives the mismatch between electrical raster and the physical aperture grille. By counting the Moire fringes across the screen, and where they fall, you can see how many pixels the image is off by, and how that varies over the screen (the edges and corners are the worst, of course). You also see a rainbow of subtle color, because much as interference colors arise from an oily film, the rasters of different colors aren't quite identical.So it's quite important to have lowpass antialias filtering on a CRT display, to avoid drawing very sharp graphics that fall apart under these errors.LCDs completely fix the electrical-to-spacial mapping, by physically addressing each pixel (yay!). But, their very square pixels, and the high contrast ratio between neighboring pixels, can make visual problems of their own, again making antialiasing very important to the viewer. (I wonder if anyone ever thought about making a hexagonal* over-sampled and antialiased LCD. Hmm...)*A hex grid can resolve circular features properly (like the round blur of antialiasing), where a square grid cannot. Also, a hexagon is easily divided by thirds, which is nice for coloring, I guess?Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 10, 2017, 11:11:08 pm
content: Quote from: wilfred on February 10, 2017, 10:23:08 pmI still use a 1600x1200x85Hz Trinitron. I prefer the color fidelity, and haven't met a single LCD that can compare (though they're finally starting to get comparable).The highest I've seen is 2048 x 1536, which is probably the practical limit of compensating an analog raster scan system in production. The maze of correction components in one of these displays is astounding: magnetally biased saturable reactors for correcting nonlinearity, switched capacitors for correcting sweep rate and ringing; etc. And at horizontal sweep rates over 100kHz, the poor yoke is being pumped with ~1kVA of reactive energy, just to push around a nearly massless electron beam!Tim

author: helius
author_rank: Super Contributor
timestamp: February 10, 2017, 11:34:41 pm
content: Quote from: Fusion916 on February 10, 2017, 09:50:32 pmThe physical construction of the tube is that it should have an aspect ratio that is close to 4:3for broadcast signals that are in that aspect ratio, or else the image will appear distorted. The physical tube has almost nothing to do with the 483 "visible lines", in fact on most old televisions not all those lines were visible due to overscan. The determining factor of horizontal resolution is the bandwidth and signal fidelity of the tuner, filters, and amplifiers; it was not generally constrained by the response of the electron gun, although that can play a role in displays with higher video bandwidths. "TV lines" is a measurement of the horizontal resolution that is normalized to the screen height, not to its width; this cancels out the effects of overscan or underscan, as long as the picture tube is 4:3. The "lines" are not actually pixels, but a number of alternating white and black signals that are displayed with a minimum level of contrast, similar to line pairs/mm to measure film resolution.The NTSC signal contains a specific number of lines vertically (525, of which 483 or 480 visible), but the data horizontally is a continuous signal. It might make sense to use 640 pixels to represent each line, since 640:480 = 4:3, but there is a problem because the color signal does not have an even multiple of 640 cycles per line. So in broadcast video it's standard to use 720 pixels per line, even though the pixels are not square (not the same distance horizontally as vertically).

author: Paul Moir
author_rank: Frequent Contributor
timestamp: February 10, 2017, 11:48:10 pm
content: Regarding the overscan (525 vs 480 thing) that was done so that the picture would still fill the screen even given variances in line voltage, temperature, tolerances, etc. You have to remember early TVs had not much by the way of regulation or anything like that going on, and were optimized for the minimum number of tubes.If you scan a normal picture tube at 480/30fps, then by the time the last line on the bottom of the screen is being swept the top line is dimming. That's why they went with interleaved in the first place: to prevent noticeable flicker.Tube shape has a lot to do with vertical resolution. Even before LCD everyone hated a deep TV, so the electron gun was squashed up close to the screen. As a consequence, at the top and bottom of the vertical scan the electron beam hits the phosphor at a steep angle. This causes the lines near the top and bottom to be larger. Think sloped tank armour. You'll notice high resolution CRTs such as in computer monitors were much deeper to prevent this.

author: helius
author_rank: Super Contributor
timestamp: February 10, 2017, 11:53:39 pm
content: Quote from: T3sl4co1l on February 10, 2017, 11:11:08 pmThere were higher resolution displays used for specific applications. The Sony DDM-2802C had 2Kx2K used for air traffic control. 4Kx4K might have been sold, but I was unable to find documentation. There was agovernment grantin 1992 to fund development but nothing seems to have come of it.

author: helius
author_rank: Super Contributor
timestamp: February 11, 2017, 12:06:18 am
content: Quote from: Paul Moir on February 10, 2017, 11:48:10 pmThat's a good point; a lot of televisions did have very shallow tubes. Although few were as thin as the SinclairTV80!On the other side, oscilloscopes had really nice, wonderfully long tubes.

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2017, 01:14:08 am
content: I think this has been mostly covered, but the primary limiting factors of the tube itself are the spot size and the pitch of the shadow mask or aperture grill. For monochrome tubes the only real limit is the spot size; the phosphor screen on those tiny 0.5" viewfinder tubes is essentially the same as on a 25" B&W TV tube but the viewfinder tube can produce a far smaller spot, at the expense of much lower total energy.For the whole system, the vertical resolution is determined by the number of scan lines which is determined by the ratio between the vertical and horizontal sweeps. The horizontal resolution is determined by the bandwidth of the video amplifier and that of the image source.CRTs are a fascinating technology and it's sad to see them disappearing so rapidly. I'm of the opinion that for viewing analog content nothing else comes close to a CRT, and the picture looks much better than the specs on paper would suggest. There are a few other tricks they can do too, the light guns used in some classic video games rely on the raster scanning of the CRT to identify where the gun is pointed. An even more impressive use is the CRT vector monitor, if you've never played Atari's 1979 arcade game Asteroids on an original CRT vector monitor you've never really played it. They used velocity modulation to create eye-searing bright photon bullets that streak across the screen. If you play it emulated on a raster monitor it's nowhere near the same.

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2017, 04:18:15 am
content: Quote from: Fusion916 on February 10, 2017, 09:50:32 pmIgnoring linearity and sticking with monochrome CRTs, the spot size determines the number of lines of resolution which is an easy enough test to make using a raster.QuoteExcept for constraints on how quickly the beam can be scanned and controlled, the CRT design has no influence on progressive versus interlaced display formats.Quote from: wilfred on February 10, 2017, 10:23:08 pmOscilloscope CRTs are long (for their target area) because deflection sensitivity which limits bandwidth is proportional to length.A major limitation of bandwidth in oscilloscope and scan converter CRTs is charging and discharging the deflection plates to relatively high voltages. The best scan converter CRTs limited to a length suitable for rack mounted equipment were about 5 GHz. During the cold war, the Soviets had a much easier solution; they made scan converter CRTs which were 6 meters long to achieve a bandwidth of 13 GHz.QuoteThere are a bunch of things which affect the spot size. Lower acceleration voltages mean that the electrons have more time to mutually repel each other. (1) Different types of electron lenses suffer from various amounts of aberration. If scan expansion is used, it also expands the spot size. (2) The phosphor target itself diffuses the spot. (3)(1) So higher acceleration voltages yield both a smaller and brighter spot.(2) This explains why the last generation of pre-scan expansion mesh CRTs (50 MHz Tektronix 547) have a smaller spot size than later CRTs. On the other hand, scan expansion meshes yielded higher bandwidth because of higher deflection sensitivity. Some later CRTs replaced scan expansion meshes which quadrupole lenses but I think they bend up the beam a lot because they have little or no increase in sharpness. Or maybe my one oscilloscope like this is just old.(3) The bright disc around the spot seen at low sweep speeds is from secondary emission; the electrons blasted free from the spot get pulled back by the high PDA (post deflection acceleration) voltage. The ghost seen at low sweep speeds which catches up to and then precedes the spot is produced by (secondary emission from?) the electron beam hitting the scan expansion mesh.Quote from: T3sl4co1l on February 10, 2017, 11:06:39 pmIf you ever have the pleasure of working on an oscilloscope which supports reduced scan, then you can see the effect of the acceleration voltages on the sharpness and brightness. Increasing the cathode voltage (more negative) makes the focus proportionally sharper, incredibly so, but also lowers the deflection sensitivity proportionally.I do not know why someone could not in theory have made a lower bandwidth higher deflection sensitivity CRTs with a higher cathode voltage and tiny spot size across a standard 10x8cm or larger graticule but I do not know of any. I assume diffusion through the phosphor target would have limited the improvement.Lowering the PDA lowers the brightness and increases the spot size of course but counter intuitively also changes the deflection sensitivity because it acts as a final lens. If a scan expansion mesh is used, lowering the PDA counter intuitively *lowers* the deflection sensitivity. The Tektronix Circuit Concepts book on CRTs discusses this.I did a bunch of tests on my 7904 and 7603 last year to see what effects altering the PDA has so we would have a better idea of what to look for on the TekScopes@yahoogroups.com list when someone suspects a missing PDA or bad high voltage multiplier.Quote from: T3sl4co1l on February 10, 2017, 11:11:08 pmI have a 21" shadow mask computer monitor which does 2048 x 1536 but I usually ran it at 1600x1200 to match my 19". Its horizontal output circuit keeps failing.

author: helius
author_rank: Super Contributor
timestamp: February 11, 2017, 04:55:35 am
content: Quote from: David Hess on February 11, 2017, 04:18:15 amSomething similar happens in storage CRTs, right? The second electron gun is focused to spread out evenly over the whole face, and somehow kicks electrons from a dielectric layer out to strike the phosphor. There were also some regular tubes that used flood electrons to light the graticule!QuoteI have two monitors with issues that I need to diagnose. One has visible green lines in the retrace: I hope it's just a bad blanking circuit, but I'm afraid there could be something wrong with the guns.The other has helpful MCU error messages, but I have no idea what "Malfunction: ELT down" means. Extra low voltage??Quote from: james_s on February 11, 2017, 01:14:08 amLight pens should also work on vector monitors, if the display list can be synchronized with the pen input. You can only "click on" active drawn lines or points; raster scan has the advantage that you can detect clicks anywhere if the raster is turned up enough for the pen to detect.

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2017, 06:26:29 am
content: I suppose a light gun could work on a vector monitor, I never saw it done but it's certainly possible from a technical standpoint. I suppose I should have just said that only a CRT display will work.I doubt the retrace problem with your monitor is a problem with the guns. Usually it's either a problem with the blanking or excessive sub brightness.

author: helius
author_rank: Super Contributor
timestamp: February 11, 2017, 07:24:24 am
content: Quote from: james_s on February 11, 2017, 06:26:29 amI seem to remember that SAGE (on the AN/FSQ-7) and Sketchpad (on the TX-2) both had light pens. They were vector display based.QuoteRight, but if the AGC is compensating for a blown gun it could overpower the blanking.

author: Siwastaja
author_rank: Super Contributor
timestamp: February 11, 2017, 10:10:23 am
content: Quote from: james_s on February 11, 2017, 06:26:29 amAt least several Sony computer monitors tend to have an issue with a failing G2 HV regulator (around 1 kV IIRC), producing increasing G2 voltage, causing overall brightness increase that cannot be compensated with the brightness controls - eventually even the retrace appears. I tried to properly fix my Sony, and the schematics for the HV regulator, IMO, were showing overly complex design for such a simple linear regulator. I ended up kludging some resistors somewhere in the circuit to drop the G2 back to acceptable levels before I ditched the monitor.What defines the actual resolution of the CRT, is the focusing of the electron beam so that it can produce a small enough dot in every part of the screen. It can be fairly complex combination of electrostatic focusing (focus voltage applied to the tube), static astigmation magnets that can be adjusted (typically small gray plastic levers in the neck of the tube), and electromagnetic focus coils dynamically driven and adjusted for different parts of screen, controlled digitally. In a typical computer CRT, most of these things are hidden from the user or nonexistent - but getting a high-end CRT projector allows you to become very familiar with all the gazillion of adjustments and settings (mechanical, analog and digital) and how they affect the image. With CRT projectors, 1600x1200 is often considered "mid range" resolution (such as my Barcographics 808s); some go considerably higher, but "normal" CRT stuff tends to stop before 4K. But I'm rather sure there are hyperexpensive specialty units produced only in hundreds that can do 4Kish with crisp image. For real-world examples of mass produced CRT projectors, seehttp://www.curtpalme.com/Projector_Rankings.shtm

author: CJay
author_rank: Super Contributor
timestamp: February 11, 2017, 10:35:18 am
content: Quote from: David Hess on February 11, 2017, 04:18:15 amI was under the impression that another reason the tubes are long is because a narrow deflection angle is easier to keep linear across the scan, shorter tubes necessitate wider deflection angles and are proportionally more difficult/expensive to keep linear, also electrostatic deflection is less 'powerful' than magnetic deflection (but much easier, again, to keep linear)?

author: nctnico
author_rank: Super Contributor
timestamp: February 11, 2017, 11:52:18 am
content: Quote from: Fusion916 on February 10, 2017, 09:50:32 pmFrom an electronics perspective the resolution is limited by the speed of the horizontal sweep. A higher resolution needs a faster sweep to draw more lines in the same time for a given framerate. Another key component is the amplifier which modulates the output of the electron guns. These need high voltages and achieving high frequencies and good linearity makes these amplifiers expensive.Also getting a sharp picture on the entire tube is difficult. Eizo had a system in their higher end monitors which controlled the focus dynamically during sweeping so the picture is sharp right into the corners. Someone else already mentioned Trinitron but that always gave me a headache. The best CRT monitors I've seen are the LG Flatron types. Even after years of use the picture is still sharp.

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2017, 01:24:07 pm
content: Quote from: helius on February 11, 2017, 04:55:35 amYes, secondary emission from the flood gun plays a critical role in storage CRTs. I just thought this was interesting because it is an example where one can literally see the results of secondary emission. Unlike the spot from the electron beam, the disc produced by secondary emission has uniform brightness and a sharp boundary.Quote from: CJay on February 11, 2017, 10:35:18 amAs far as I know, that was never an important consideration. There are various things which can be done with the electron optics to improve linearity, reduce aberration, and increase deflection sensitivity but deflection sensitivity and effectively bandwidth are proportional to tube length and bandwidth was always a problem.Image CRTs are a completely different matter since they are not limited by deflection sensitivity do to their low bandwidth requirements and there is a high premium on having a large area while being short. As nctnico points out, their horizontal resolution is limited by their z-axis bandwidth which is completely different from an oscilloscope CRT although they are not slouches for z-axis bandwidth either.

author: Moshly
author_rank: Regular Contributor
timestamp: February 11, 2017, 02:34:53 pm
content: This Tek video discuses some of the issues involved in making CRT's

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2017, 05:09:39 pm
content: Fascinating! No wonder Tek analog scopes were so expensive.

author: _Wim_
author_rank: Super Contributor
timestamp: February 11, 2017, 08:37:51 pm
content: Quote from: Moshly on February 11, 2017, 02:34:53 pmThanks for posting this one! Makes you appreciate gear like this even more!

author: Audioguru
author_rank: Super Contributor
timestamp: February 12, 2017, 01:43:35 am
content: Years ago my Sony 32" Trinitron flat screen TV failed. I tried to fix it but it failed again. I thought it was pretty good so my son bought me a new one that was also pretty good.I was given an LCD high definition TV for the recent Christmas and it ismuch[/b clearer that the Sony CRT TVs that had standard definition.I wrongly assumed that my cable TV company would charge more for high definition but no, it is standard now. Next year I might receive a 4k or 8k TV for Christmas.

author: james_s
author_rank: Super Contributor
timestamp: February 12, 2017, 06:30:55 am
content: You can get HD over the air for free, have been able to for years.For standard definition content a good CRT still looks superior, but there's no shortage of HD content anymore.

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: February 12, 2017, 10:05:46 am
content: Siwastaja:For the Sony CRT monitor issue-From memory one needs to download Sony DAS (digital alignment software) and use a TTL to RS232 converter from the DB9 port hidden round the side of the monitor. The G2 voltage and many other adjustments can then be made.I have done this on a couple of G1 chassis over the years.BT

author: tooki
author_rank: Super Contributor
timestamp: February 12, 2017, 10:36:17 am
content: Quote from: wilfred on February 10, 2017, 10:23:08 pmI know Barco made 3-CRT projectors that could exceed 1080p. (Never saw one in operation though.)Speaking of weirdo projectors that are technically CRTs, though not in any form resembling a "normal" CRT: who remembers theEidophor? Now that was cool technology if ever there was one!

author: Siwastaja
author_rank: Super Contributor
timestamp: February 12, 2017, 01:32:58 pm
content: Quote from: tooki on February 12, 2017, 10:36:17 amNothing special exceeding 1080p on a CRT projector! These over-full-hd units are surprisingly commonplace, from many manufacturers, often considered mid-range units. My Barco exceeds 1080p, and scans to 1200 lines at 100Hz, although I use it at 1080p since going further doesn't give much extrarealresolution with this mid-range, slightly worn-out 8" unit; at least it would require very careful and experienced setup, so I'm happy with the standard full-HD input.Exceeding about 1400-1500 scanlines with a crisp image, getting near to the 4K territory (but not quite) would bring you up to the high-end CRT projectors, which are expensive, special, and somewhat rare, but still not "legendary" magical things; still several manufacturers and models to choose from!And a good, high-end CRT projector still exceeds the visual image quality of even some of the new, expensive DLP projectors when displaying natural (sampled) images where square-pixel mispresentation of the sampled analog image is not desired. OTOH, when computer graphics and text are to be presented, often in a brightly lit conference room, CRT projector is totally wrong tool for the job, which is why mid-to-high-end CRT projectors from the late 90's and early 2000's are being decommissioned from such environments, often in useable shape.

author: tooki
author_rank: Super Contributor
timestamp: February 13, 2017, 01:39:15 am
content: Yeah, I mean, I remember occasionally running 1600x1200 on my 19" DiamondTron computer display back in the day. The resolution-limiting factor in CRT systems would be the drive electronics, no? (And the dot size of the beam of course.)

author: David Hess
author_rank: Super Contributor
timestamp: February 13, 2017, 02:20:47 am
content: Quote from: tooki on February 13, 2017, 01:39:15 amThere are three limits:1. The CRT spot size.2. The grill pitch on a color CRT.3. The z-axis bandwidth which is proportional to the horizontal resolution times the horizontal scanning frequency.

author: Siwastaja
author_rank: Super Contributor
timestamp: February 13, 2017, 08:58:32 am
content: Quote from: David Hess on February 13, 2017, 02:20:47 amAnd with CRT projectors, this doesn't exist; but there still is the limitation of making super-accurate and non-drifting per-color convergence control so that the RGB images end up exactly on the top of each other. Higher end projectors use hundreds of lookup table points to finetune the picture geometry per color at arbitrary points, and of course, it takes some patience to adjust each of the points so that the test pattern lines match! In principle, the same is of course true with the desktop monitor, but it's a lot easier to deal with (so there are fewer adjustments and they are either factory-fixed or behind a secret menu).I think the spot size is rather easy to get small enough in desktop monitors, because there is no issue displaying 1920x1080 image on a small 8" CRT projector tube withmassiveintensity (something that almost blinds you if you looked at it directly). The DPI is huge there; from this perspective, it's a lot easier to display 4K on a 21" tube.But the spot size and shapeat the cornersis a challenge in desktop monitors, because they cannot use the same shape as the CRT projector tubes, as the monitor would be 2-3 meters deep. The projector tubes, while only 7 to 9 inch, are actuallylongerthan the 21" monitor tubes!

author: dexters_lab
author_rank: Unknown
timestamp: February 13, 2017, 11:56:06 am
content: back in the late 1980s Quantel used CRTs that far exceeded 1080 HD resolution, IIRC they were made by Sony.They were used with the Quantel Graphic Paintbox that famously did the artwork for Queen's The Miracle album cover.

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2017, 04:54:23 pm
content: Exceeded 1080p in the late 80s? I find that hard to believe. At that time 1280x1024 was considered extremely high resolution, found only on high end workstations like Sun and SGI. I never saw anything higher until a decade later.

author: tooki
author_rank: Super Contributor
timestamp: February 13, 2017, 05:30:09 pm
content: Quote from: james_s on February 13, 2017, 04:54:23 pmI think it's plausible — I remember a mention of the Quantel Paintbox in a German computer magazine in the early-mid 90s, where they described them as costing a fortune and having "displays the size of living room windows". They managed this by brute force, throwing tons of hardware at the problem.I just found this1987 magazine articleabout it: "Quantel has developed a version of Paintbox which has enough resolution to make it suitable for the printing industry.Its screen has 2000 linesas opposed to the 625 lines of a television screen. At a starting price of £250,000, Graphic Paintbox costs four times as much as the standard model."

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2017, 05:57:43 pm
content: That's crazy! I wonder if that was interlaced? I'd love to find out more about those machines, I've had a bunch of Sun and SGI stuff but never owned anything like that.

author: SimonR
author_rank: Regular Contributor
timestamp: February 13, 2017, 09:42:24 pm
content: Quote from: james_s on February 13, 2017, 04:54:23 pmAnd Japanese Analogue HD TV. It was called the MUSE system branded as Hi-Vision by NHK1125 lines 1035 visible interlaced. it was developed in the very late 70s early 80s, demonstrated in the mid 80s and broadcasting by the end of the 80s. I remember the announcement of the research program and saw a demonstration of around 1990 at a trade show. It was really impressive for the time.https://en.wikipedia.org/wiki/Analog_high-definition_television_systemhttps://en.wikipedia.org/wiki/Multiple_sub-Nyquist_sampling_encodingAlso you're right about high end workstations in 1988 PCs were still using EGA, maybe VGA but our PCB CAD system ran on Apollo workstations with 1280x1024 16 million colour monitors. I never did find out how much they cost

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2017, 11:22:05 pm
content: I don't know how much the Apollo workstations cost, but I have a Sun Sparcstation IPC that I gather originally cost $12,500 for the system unit and then the Sony manufactured monitors were several thousand dollars on top of that. We still only had CGA on the family PC at that point.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 14, 2017, 12:22:57 am
content: Quote from: james_s on February 13, 2017, 04:54:23 pmhttps://en.wikipedia.org/wiki/Sony_HDVS

author: james_s
author_rank: Super Contributor
timestamp: February 14, 2017, 12:24:57 am
content: That is quite a technological achievement, although interlaced 1125 line is still substantially less bandwidth than 1080p despite slightly more lines.