TVL when pressing the 16:9 switch

[PogOrion]

I understand the concept of TV Lines on a 4:3 CRT display. But what happens to the number when you hit the 16:9 button? Does it stay the same, or is it now 9/16 of the height of the 16:9 image taking into account the TVL number for the display in normal 4:3?

So if we have a 800 TVL CRT.
800 X 9/16 = 450 TVL?

[Xer Xian]

TVL are the B&W lines that can be counted on a horizontal span equal to the picture height, so yeah the number changes according to the aspect ratio. If you want the number of lines over a 16:9 AR, multiply the reported TVL by 0.75 (= 4/3 * 9/16).

It doesn't really matter though - the monitor will resolve the same horizontal definition regardless of the aspect ratio.

[PogOrion]

So if a system, such as an Xbox 360, automatically letterboxes a 4:3 image, creating a 16:9 image, are the TV Lines counted on the horizontal plane equal to height of the whole 4:3 image, or just the new 16:9 image?

[Xer Xian]

I guess that the black borders are technically a part of the picture in that case, but really.. why do you care? It doesn't matter at all. The TVL count is only meant to measure the max horizontal definition that can be fully resolved by CRTs, which are analog and don't have a fixed number of pixels.

[Unseen]

So if a system, such as an Xbox 360, automatically letterboxes a 4:3 image, creating a 16:9 image, are the TV Lines counted on the horizontal plane equal to height of the whole 4:3 image, or just the new 16:9 image?

A 4:3 image is a 4:3 image even if it is partially or entirely black.

[PogOrion]

The TVL count is only meant to measure the max horizontal definition that can be fully resolved by CRTs, which are analog and don't have a fixed number of pixels.

For a 240p image, is it true if the TVL count is less than 240, then definition will be lost? Or will it not display at all?

[Lawfer]

If your TV is in 4:3 mode it will display at it's max TVL regardless wether or not the game is outputted in widescreen, take for example a few games on Wii.

It will loose TVL if the TV or monitor itself change to 16:9 mode.

[Xer Xian]

For a 240p image, is it true if the TVL count is less than 240, then definition will be lost? Or will it not display at all?

No, that's the vertical resolution (number of scanlines).

To find the max detail that a CRT can resolve horizontally you should multiply the TVL count by 1.33 (= 4/3). As an example, with 600 TVL you get a total hor.res of 800, which is more than enough for SD material.

[PogOrion]

Is that only for 4:3 displays? And if so would that mean for a 16:9 CRT display you would multiply the TVL by 16/9?

[Xer Xian]

Yes

[FinalBaton]

If you check a Sony manual (BVM brochure comes to mind) :

widescreen monitors have the same TVL count when displaying 4:3 or 16:9

4:3 monitors have a bit less TVL in 16:9 than in 4:3

[Lawfer]

4:3 monitors have a bit less TVL in 16:9 than in 4:3

-200TVL is quite a significant downgrade.

[FinalBaton]

-200TVL is quite a significant downgrade.

It is a significant drop indeed

[Xer Xian]

Again, the drop in the TVL count does not correspond to any drop whatsoever in the actual resolving power of the CRT - it's just a consequence of the fact that the lines are counted inside a perfect circle inscribed into the (viewable) display.

If you want to be real picky about resolution measurements, it's probaby worth reading about the kell factor instead, and differentiating full from effective resolution. Due to TVLines being a 'perceptual' measurement, it doesn't have any bearing on their count, but it's indeed a limiting factor in the vertical resolution. It also applies to digital displays (in both axes).

[Lawfer]

-200TVL is quite a significant downgrade.

It is a significant drop indeed

On the Sony BVM-D/A 20" 240p, 288p, 480i, 576i, 480p all output in either 4:3 and 16:9, at 4:3 you get the full 900TVL, while if you switch to 16:9 you get only 700TVL.

Any resolution above 480p is 16:9 ONLY, basically the Sony BVM-D/A won't offer you a 4:3 HD resolution like 960x720 (of course you can adjust the settings to get a 960x720 picture to display properly on the screen, but it will be 700TVL since it is technically in 16:9 mode), so for anything higher than 480p it's 700TVL only.

Howver on the Sony BVM-D/ 24" and 32", it's 1000TVL across the board, wether it's 4:3 or 16:9.

This is only for the Sony BVM series though, for example on the Ikegami HTM series, you can't get 480p in 4:3 mode, only in 16:9 mode but of course like with the BVM-D/A you can adjust it, you just won't be having 900TVL+ like you would in 4:3 mode.

[FinalBaton]

Again, the drop in the TVL count does not correspond to any drop whatsoever in the actual resolving power of the CRT

Of course not.

But on the 4:3 bvm, the area "as wide as high" for widescreen content is smaller than the one for 4:3 content. Whereas on the 16:9 bvm, that area is the same for both 4:3 and widescreen content. Hence the similar TVL count for both aspect ratios on the 16:9 bvm, and the dip in TVL for 16:9 material on the 4:3 bvm. ANd that of course mean that a 16:9 game on the widescreen bvm will benefit from more rows of phosphors than on a 4:3 bvm.