Why were most crt TVs classified as 4:3 when they were 3:2?

[Lawfer]

As Fudoh once mentioned here most CRTs were basically made for 480i as the main resolution, which follows the DVD standard at the time 720x480, however 720x480 is technically not 4:3, but actually 3:2 and 3:2 has a higher length than 4:3, 320x240 and 640x480 are both 4:3.

From what I gather 3:2 TV are actually the standards as they provide compatibility for all these resolution, 320x240, 640x480 and 720x480, while true 4:3 screens can't provide proper compatibility for 720x480 as it would result in a picture that's missing quite a bit on the right and left side, however this also explain why you would notice that the games aren't filling the whole screen such as it's been asked here: http://shmups.system11.org/viewtopic.php?f=6&t=58606 and that's even with games that present no underscan but displays as full screen, the most likely reason would be that you are playing a 4:3 game (pretty much every or almost every PS1 and Saturn games) on a 3:2 screen resulting in black bars on the left and right side of the screen.

Example:

640x480:


720x480


Some Original Xbox games are 640x480 and some are 720x480, in most cases unless you possess a 4:3 PC monitor or professional monitor (such as the PDP-V402), the 640x480 games will display with blacks bars on the left and right side while the 720x480 games will display full screen.

Of course, the best thing to do is to own a 3:2 crt which is what most people actually have, for the highest compatibility across both aspect ratio. however isn't it misleading for manufacturers to sell 3:2 crts as 4:3? Or did I get something wrong?

[ZellSF]

Pixels don't have to be square. 720x480 is a 4:3 resolution (and a 16:9 resolution) and most CRTs sold were 4:3.

[Extrems]

Background information on 720 samples per line: https://tech.ebu.ch/docs/techreview/tre ... 1_wood.pdf

[Guspaz]

I'm not sure that anybody ever made a 3:2 TV. There have been some 3:2 handheld and computer displays, but TVs were universally 4:3 or 16:9.

As has been pointed out, 3:2 resolution images were always displayed with a 4:3 or 16:9 picture aspect ratio due to non-square pixels.

[Xyga]

Indeed, a number of older smartphones and the Microsoft Surface series are 3:2

[Lawfer]

But what I am saying is according to aspect ratio calculator, the results says that 640x480 is 4:3 while 720x480 is 3:2, 640x480 content cannot scale completely to 720x480 without stretching the picture which would result in a distorted image or cut off the top and bottom to crop the picture to full screen.

From the way it seems on most other crts, when you play 320x240 games or 640x480 games (true 4:3 resolutions), there are black bars on the left and right side to account for the disparity between 640 and 720, the height is the same (480) but the length (720) is different as 720 - 640 = 80, meaning it's 40 on the left and right side to display a 4:3 resolution on a tv which expects a 720x480 resolution (which according to aspect ratio calculator is 3:2).

PS1 is 320x240 which is 1/4 of 640x480, to display such resolutions on a crt that was also manufactured for 720x480 resolutions, the following workarounds would have to be taken:

- The image height will stay unchanged, since 1 * 480 is still 480.
- Pad the image with black vertical bars on the sides so that the frame width will become 720.

[Ikaruga11]

Because they are 4:3 and not 3:2.

640x480 (4:3) has no letterboxing on a 4:3 TV.
720x480 (3:2) has slight letterboxing on a 4:3 TV.
854x480 (16:9) has letterboxing on a 4:3 TV.

[Lawfer]

Because they are 4:3 and not 3:2.

640x480 (4:3) has no letterboxing on a 4:3 TV.

720x480 (3:2) has slight letterboxing on a 4:3 TV.

For me it's the other way around, 720x480 I get no letterboxing at all, while 320x240 and 640x480 I get vertical letterboxing. (that's only for games who use no underscan in-game, for games such as Final Fantasy VI on PS1 there are black bars on all sides because the game use a high amount of underscan).

And for 720x480 (3:2) displaying on a screen whose resolution is 640x480 (4:3), you are actually effectively losing vertical information on each side to accommodate a wider resolution to display on a slimmer resolution screen, this is what happens when you hook a Dreamcast through VGA Box to a computer monitor who's 640x480 (4:3) instead of 720x480 (3:2).

854x480 (16:9) has letterboxing on a 4:3 TV.

Obviously since you are displaying a rectangular-ish aspect ratio on a square-ish TV.

[FinalBaton]

What Guspaz said.

720x480 is a DV/DVD resolution that what created for the digital domain. The pixels in that format are not square, they are narrower. 720x480 makes for a 4:3 raster.

And SD TVs were 4:3.

[ZellSF]

But what I am saying is according to aspect ratio calculator, the results says that 640x480 is 4:3 while 720x480 is 3:2, 640x480 content cannot scale completely to 720x480 without stretching the picture which would result in a distorted image or cut off the top and bottom to crop the picture to full screen.

There is no reason to scale 720x480 content to 640x480.

Content made for 720x480 is displayed at 720x480, which is a 4:3 aspect ratio.
Content made for 640x480 is displayed at 640x480, which is also a 4:3 aspect ratio.

These resolutions just have different pixel aspect ratio (720x480 has wider pixels). CRTs can have pixels in any shape without stretching or distorting the image.

[Lawfer]

There is no reason to scale 720x480 content to 640x480.

No it's to scale 640x480 to 720x480 not the other way around, the reason would be the avoid padding with vertical black bars as I explained in my two last posts.

Content made for 720x480 is displayed at 720x480, which is a 4:3 aspect ratio.

According to aspect ratio calculator it is 3:2 though, not 4:3. You can clearly see that 720x480 is quite a bit wider than 640x480, unlike 320x240 which scales perfectly to 640x480.

[ZellSF]

Again, 720x480 uses non-square pixels. It's 4:3.

https://en.wikipedia.org/wiki/Pixel_aspect_ratio

And there's no reason to scale 640x480 to 720x480 either. If a display can display 720x480 natively, it can also display 640x480 natively.

[Unseen]

As Fudoh once mentioned here most CRTs were basically made for 480i as the main resolution, which follows the DVD standard at the time 720x480, however 720x480 is technically not 4:3, but actually 3:2 and 3:2 has a higher length than 4:3, 320x240 and 640x480 are both 4:3.

Here is your first misconception: A CRT does not have a notion of discrete "pixels" in the horizontal direction, it only has discrete lines in the vertical direction.

The analog TV standards date from a time when the pixel had not been invented yet, so there are no discrete pixels in an analog TV signal - instead, the length of a line is defined by the time between the end of one horizontal sync pulse and the start of the next one (ignoring blanking for simplicity). During this time, the electron beam of a CRT simply sweeps from left to right over the entire width of the tube and the video signal can change its level to indicate how intense the electron beam should be at this time, resulting in a brighter or darker spot on screen (also ignoring color for simplicity). There is no requirement for the analog signal to change its level at some discrete time within a line, instead it can change at any time since it's analog. There are limitations on the fastest possible brightness changes within a line, but I'm currently struggling to come up with a way to explain that without invoking differentials or frequency-domain considerations.

The digital video resolutions you keep referring to divide this horizontal line length into discrete time intervals and allow brightness changes only at the boundaries of these time intervals. A CRT doesn't care about this distinction however - it just sees the timing of the horizontal syncs and adjusts its electron beam sweep speed so it covers the entire width of the tube. With identical timing, the CRT sees absolutely no difference between a signal with 640 or 720 horizontal pixels - it's just that in one case the signal is able to change a bit more often during a line than in the other case.

You may have noticed that the entire discussion above is just about a single horizontal line, without any consideration for the other lines in a field/frame. This is because the number of vertical lines in a video signal does not influence the horizontal sweep range of a CRT. Your attempts to calculate an aspect ratio from a pixel count assumes that there is such a relation, but there actually is not.

The square pixels you assume are a relatively recent thing - they simplify some things, but there is no technical requirement for pixels to be square. In the PC space, most graphics modes used non-4:3 pixel counts (VGA's 640x480 is one of the earlier examples of a 4:3 pixel count mode), but basically all of them were meant to be displayed full-screen without borders on a 4:3 screen - even ones like the 720x348 of a Hercules card or 640x200 from CGA. The Commodore Amiga even supports a hires mode with 1280x240 with TV-compatible timings which was meant for display in a 4:3 aspect ratio, resulting in very rectangular pixels.

(Fun fact: Plasma screens with a 16:9 display aspect ratio and 1024x768 pixel resolution exist. Feeding them a 720p signal results in no black borders.)

[Xyga]

(Fun fact: Plasma screens with a 16:9 display aspect ratio and 1024x768 pixel resolution exist. Feeding them a 720p signal results in no black borders.)

Little OT story time:
You remind me that once years ago, I've seen one sitting in a shop along plenty of what were Full-HD LCDs, I think that was sometime during the early days of the 3D/stereoscopy craze.
A salesperson told me it was something they'd excavated from their very oldest stock. It was 37" something and the sight next to those shiny 3DHD sets was almost hilarious, I could literally count the dots without using a magnifier nor squinting my eyes too hard.

[orange808]

Further reading here:

https://en.wikipedia.org/wiki/Raster_scan

[yxkalle]

In Europe we use 720x576 as the resolution of our DVD's. That must mean our TV's are 4:5!!

[Lawfer]

Then I don't understand why I get black bars on the left and right side, I just did some measurements of my CRT, drew a figure on my PC based on these measurements and compared them with 640x480 and 720x480 pictures and it appears that the height and width of my crt fits perfectly to 4:3 such as the height and width of 640x480 but NOT of 720x480.

Please take a look, shape of my CRT made with measurements (only the white area):



Shape of a 640x480 picture:



Shape of a 720x480 picture:



Don't mind the black bars, these were screenshots scaled and taken on my 1920x1200 monitor screen, so the pics were upscaled to 1200 and added black bars on the sides to not distort the picture.

As you can see my monitor screen shape and the shape of a 640x480 picture are the same shape, so my screen is indeed a 4:3 one just as classified. But then I have no clue why 4:3 content such as PS1 and Original Xbox games that run at 640x480 displays with black bars on the left and right sides even though the measurements of my screen align perfectly to 4:3 (320x240 and 640x480) while 3:2 content such as 720x480 games or US DVD displays at full screen.

[ZellSF]

You get black bars on the left and right side because your source has them. Probably to compensate for overscan.

Alternatively, your CRT is calibrated differently for 640x480 and 720x480.

[Lawfer]

You get black bars on the left and right side because your source has them. Probably to compensate for overscan.

Alternatively, your CRT is calibrated differently for 640x480 and 720x480.

"My source" is my PS2 when I play PS1 games or my Original Xbox when I play 640x480 games (Panzer Dragoon Orta and Otogi 2 for example), some games do have in-game underscan (Final Fantasy VI, Saga Frontier 2, Threads of Fate and the likes ) and in that case the black bars on the left and right sides are increased in size, but some don't have any underscan (such as Vanguard Bandits for example) and no matter the situation I get black bars on the left and right sides. Do you get black bars on the left and right sides when you play PS1 games on your broadcast monitor?

[ZellSF]

You get black bars on the left and right side because your source has them. Probably to compensate for overscan.

Alternatively, your CRT is calibrated differently for 640x480 and 720x480.

"My source" is my PS2 when I play PS1 games or my Original Xbox when I play 640x480 games (Panzer Dragoon Orta and Otogi 2 for example), some games do have in-game underscan (Final Fantasy VI, Saga Frontier 2, Threads of Fate and the likes ) and in that case the black bars on the left and right sides are increased in size, but some don't have any underscan (such as Vanguard Bandits for example) and no matter the situation I get black bars on the left and right sides. Do you get black bars on the left and right sides when you play PS1 games on your broadcast monitor?

How much black bars you get in any direction is dependent on how you calibrated your CRT.

[BONKERS]

You get black bars on the left and right side because your source has them. Probably to compensate for overscan.

Alternatively, your CRT is calibrated differently for 640x480 and 720x480.

"My source" is my PS2 when I play PS1 games or my Original Xbox when I play 640x480 games (Panzer Dragoon Orta and Otogi 2 for example), some games do have in-game underscan (Final Fantasy VI, Saga Frontier 2, Threads of Fate and the likes ) and in that case the black bars on the left and right sides are increased in size, but some don't have any underscan (such as Vanguard Bandits for example) and no matter the situation I get black bars on the left and right sides. Do you get black bars on the left and right sides when you play PS1 games on your broadcast monitor?

All depends on how the CRT is set up. My 2007 Phillips CRT has no black borders on the sides. The most i've seen is space at teh tops and bottoms, specifically for games of the PS1 era which draw blank in those regions on purpose. (Arc The Lad II is an easy example).

I also have adjusted my TV through the service menu to customize the sizing as well.

So your TV just is set up weird or needs adjusting.

Again this is a TV not a monitor though. On my CRT monitors, it's just a matter of again. Adjusting the sizing in the menus.

[Lawfer]

You get black bars on the left and right side because your source has them. Probably to compensate for overscan.

Alternatively, your CRT is calibrated differently for 640x480 and 720x480.

"My source" is my PS2 when I play PS1 games or my Original Xbox when I play 640x480 games (Panzer Dragoon Orta and Otogi 2 for example), some games do have in-game underscan (Final Fantasy VI, Saga Frontier 2, Threads of Fate and the likes ) and in that case the black bars on the left and right sides are increased in size, but some don't have any underscan (such as Vanguard Bandits for example) and no matter the situation I get black bars on the left and right sides. Do you get black bars on the left and right sides when you play PS1 games on your broadcast monitor?

How much black bars you get in any direction is dependent on how you calibrated your CRT.

It's a broadcast monitor, so like almost everybody here unless you a have few tens of thousands bucks laying around you most probably bought it used where it was already calibrated by an editing/mastering studio.

I am not an expert at calibration or anything though, so would it be possible to "calibrate" by a non-expert (me) whitout messing it up for it to output 320x240 and 640x480 fullscreen (at least for the games who don't make use of any underscan) as it should (since it's a 4:3 screen afterall)?

Would posting pictures of my "issue" help in any way?

Thanks in advance.

[gray117]

? Dvds followed crt and had multiple resolution standards. Most crts are actually defined by number of vertical scan lines they were capable of. A crt does not have a fixed number of pixels as such - just a fixed range of freqencies it is capable of handling (in general - shadow mask / dot pitch etc will limit it to a maximum): It's better to think of it like a film/projector screen that a beam is physically moving across ...

Every time you change the signal you will have to adjust your crt for a 'perfect' image. Signal is not limited to resolution and vertical frequency - these are arguably the most important - many small variances in other parts of the signal can produce quite different geometry depending on your device.

The best you're going to find is a number of devices that your monitor deals with in a similar manner, at certain resolutions/formats/inputs and has a small element of over/under scan between devices/resolutions.

Very few screens (even pro) had the ability to store/save multiple geometry options. Nearly everyone just made do with varying amounts of over/under scan.

Your crt is more is like an analogue focusing device (like a telescope/binoculars attempting to adjust to different eyes/distances) than a digital per pixel mapping device.

[Lawfer]

? Dvds followed crt and had multiple resolution standards. Most crts are actually defined by number of vertical scan lines they were capable of. A crt does not have a fixed number of pixels as such - just a fixed range of freqencies it is capable of handling (in general - shadow mask / dot pitch etc will limit it to a maximum): It's better to think of it like a film/projector screen that a beam is physically moving across ...

I was not focusing on pixels but more on the measurements of 4:3 vs 3:2.

For example a 4:3 screen wpi;d have a different sets of measurements compared to 3:2 screen.

640x480 equals to 17cm horizontal and 13cm vertical, while 720x480 equals 19,5cm horizontal and 13cm vertical, I was trying to find out if the reason why I was getting black bars on the left and right sides was because my screen was 3:2 instead of 4:3, but upon reassuring and comparing it is obviously 4:3 and the reason for the black bars is something else.

[Lawfer]

Okay, here is a photo depicting my problem:

This is a PS1 game (US version) running on a US PS2, outputting on my 4:3 monitor, notice the black bars on the right and left sides:



Shouldn't it be filling the whole screen?

[bobrocks95]

You just have to adjust your HSIZE in the service menu. It doesn't take a lot of knowledge to do that, especially on a broadcast display where it should be more easily accessible. I have mine set for slight overscan on all sources to take care of any variability in resolution- the games were all designed with overscan in mind anyway.

[ZellSF]

Keep in mind that due to different resolutions and amounts of overscan used by different sources (even per game!), if you make one source fill the image perfectly another might have part of its image cut off or have black bars. There is no perfect solution for this.

[Lawfer]

Yes I know I have noticed, some games have different amount of underscan depending on the situation, like one kind of underscan during gameplay, another one for CG cutscenes and so on.

So you are saying it's better to leave it like it is for the most compatibility across games?

[Sumez]

I would say the best course of action is to resize the pictures to the smallest possible that doesn't leave you any black borders. Then if another console gives you a border, make it just a big larger. That way you don't have to deal with more overscan than absolutely necessary. Most old TVs had a ton of overscan, but we never had any issues with it back then.

It's a personal preference though. Most people prefer to be able to see as much of the image as possible, and don't mind dealing with slight borders on some games.

[Lawfer]

I would say the best course of action is to resize the pictures to the smallest possible that doesn't leave you any black borders. Then if another console gives you a border, make it just a big larger. That way you don't have to deal with more overscan than absolutely necessary. Most old TVs had a ton of overscan, but we never had any issues with it back then.

It's a personal preference though. Most people prefer to be able to see as much of the image as possible, and don't mind dealing with slight borders on some games.

Most CRTs are too small for today's standards though, 21" used to be considered HUGE back then, but today it's small compared to the TVs and PC monitors so every cm counts. Heck the standards for TV sizes keeps increasing, back 10 years ago the standard was 46"-55", now it's more like 65"-75".