Still confused over 16:9 vs 4:3

[Chris Barcellos]

Here is a layman's description of the Widescreen process:

http://gregl.net/videophile/anamorphic.htm

[Boyd Ostroff]

Originally Posted by Mike Teutsch

He was asking about those with only 4:3 sets! And, I said that it would be squished down and stretched out with black bars on the top and bottom. Right or wrong?

Have a look at John Miller's post #3 on the first page. This is what happens on perhaps 98% of the 4:3 television sets in the US. Only the very newest ones are capable of letterboxing a 16:9 image. Generally speaking, a 4:3 set just fills its screen with whatever you send it.

Unfortunately, we have to get into "anamorphic" for this discussion. Remember, that simply means that the shape of the image has been changed. The camera recorded a widescreen image, but squashed it into a 4:3 frame to record it on tape. So your 4:3 TV doesn't know any better... it just displays it as though it was a full screen image. The result will be squashed, with everything looking too tall and skinny (which might not be bad, depending on who you're looking at ;-)

If you want the black bars (letterbox), the you will need to provide them for the TV. As discussed, if a DVD player is properly configured so that it "knows" it's connected to a 4:3 TV, then it will scale the image properly and add the black bars. So it's sending a correctly proportioned 4:3 image to the TV, with the 16:9 image in a letterbox.

But if you aren't distributing the video on DVD, then you will need to provide the black bars and scale the video yourself. You can do this with your editing software. Don't know about PC's, but in Final Cut Pro this is as simple as dropping your 16:9 video into a 4:3 sequence. The software will automagically letterbox it.

The downside here is for people who have 16:9 TV's; they don't get the full quality possible. Letterboxed 16:9 only uses 360 of the available 480 scan lines. There are 60 black lines above the image, and 60 black lines below it, so in other words, you're wasting 25% of the available lines. But an anamorphic image uses all 480 lines, and stretches them to the full width of a widescreen TV.

I'm not familiar with the XL2, but the Sony Z1 can be set to provide the letterbox itself when connecting the camera to a monitor. I'm not sure whether the XL2 can do this, I kinda think that it can't. But you would only want to do this if you're viewing a tape from the camera directly on a 4:3 TV.

[Gary Gonsalves]

Great information Chris and Boyd...thanks

[Mike Teutsch]

Thanks to all, great informative post!

Mike

[Kevin Shaw]

Originally Posted by Boyd Ostroff

Have a look at John Miller's post #3 on the first page. This is what happens on perhaps 98% of the 4:3 television sets in the US. Only the very newest ones are capable of letterboxing a 16:9 image. Generally speaking, a 4:3 set just fills its screen with whatever you send it.

Most people with 4:3 televisions should have figured out by now to adjust their DVD player for proper widescreen playback, unless they've never watched a widescreen movie. It wouldn't normally be up to the TV to make this adjustment, it's controlled by the player.

Just in case anyone isn't clear yet about anamorphic video, the key is that the recorded pixels contain a non-square portion of the image. That's confusing because we tend to think of pixels as being square, but in this case they're just not. As previously mentioned all DV (NTSC) video contains 720x480 recorded pixels, while basic math tells us that a 16:9 image should have 853.33 x 480 pixels (if the recorded pixels were square). So if you want 16:9 output on a square-pixel display using 720 x 480 recorded pixels, then each recorded pixel has to represent ~1.185 pixels on the horizontal axis of the display. That's the "pixel aspect ratio," which in this case would be 1.185.

Or to put it another way, if you took widescreen DV video of a wall 853 feet wide by 480 feet tall, each pixel in the recorded image would represent an area of the wall about 1.185 feet wide by 1 foot tall. If you then played that image directly on a square-pixel monitor without adjusting the aspect ratio, it would make the wall look like it was only 720 feet wide, which we know is not correct. But if your video player knows the pixels aren't square it can process them to show correctly on a square-pixel display, making the wall look like it's 853 feet wide again. Again, the key to this is understanding that the recorded pixels do not represent a square portion of the image.

This all applies whether you get the result by using an anamorphic lens to bend incoming light onto a 4:3 sensor, or using a camera like the XL2 which can interpret the data from its widescreen sensor to cram the results onto DV tape. Either way the end result is 720x480 recorded pixels with an anamorphic pixel aspect ratio of 1.185 (for NTSC). The benefit of having a camera like the XL2 is that you don't have to put a special adapter on your lens to get anamorphic widescreen recording, but it's still anamorphic widescreen recording. With the XL2 the "anamorphising" is done electronically after the light hits the sensor, rather than optically before the light hits the sensor.

Also see what Wikipedia has to say about all this: http://en.wikipedia.org/wiki/Anamorphic

[John Miller]

Don't forget, though, that 720 x 480 NTSC doesn't use square pixels for 4:3, either!

For square pixels, the dimensions would be 640 x 480 (just like VGA resolution).

Likewise, for PAL, square pixels would relate to a 768 x 576 image.

But, since DV samples at 720 pixels per line, you end up with slightly skinny pixels for NTSC (for 4:3) and slightly fat ones for PAL....


....anyhoo, I always thought a simple solution for watching squished material on a standard 4:3 display would be some inexpensive, anamorphic glasses!

[Mike Teutsch]

Great post too Kevin! This turned out one very informative thread and thanks to all who contributed. A little coaxing got out the big guns with the best of info.

The sticking point for some, me included, is that we generally never play anything back straight from the camera, or raw, to the old 4:3 TV, it is always burned to a DVD and the player makes life easier for us, and thank God for that! Even my 12 year old little 4:3 TV knows what to do then! I'm sure that the TV stations have no problem with it either.

This post is worth reading several times, and that is what I will do for sure. With all the excellent posts and great links, it almost at sticky level.

Mike

[Ken Hodson]

I have a question along the same lines as whats being discussed but with the difference being the resolution not compressed to DV. For example a native 16:9 SD cam that records component out to an uncompressed codec. Would it be 960x480 NTSC, being that it doesn't have to conform to DV spec? Always wondered about this.

[Jonathan Kirsch]

Just to throw one more chink into all this:

Many of the HDTVs (widescreen) out there have a button or feature that allows you to choose the aspect ration to view: 4:3, 16:9 (letterboxes), 4:3 expanded (scales and fills up the screen...crops pic, looses resolution), and 16:9 fullscreen.

I'm using FCP and DVDSP. I shoot in 16x9, capture to a 16x9 anamorphic timeline and export for 16x9. DVDSP is marked for 16x9. My question is...will that give me the 16:9 letterboxed or 16:9 fullscreen? I just want to use up the whole screen and not have this smaller version with letterboxes.

By the way, very informative thread!

Jonathan

[Boyd Ostroff]

That will depend on the user's DVD player and TV. If they have the player correctly setup, an anamorphic DVD will fill a widescreen TV at the highest possible resolution. If they have a 4:3 TV then the player will provide the letterbox.

But those different modes for widescreen TV's are only selectable by the person with the TV. You can't force the TV into the correct mode with standard definition footage unfortunately. So the user could set a widescreen TV to 4:3 mode and your anamorphic DVD would appear squashed in a small recatangle with a black bar to the left and right for example. Or if they set the TV to zoom mode the video would fill the width of the screen with a squashed image while chopping off the top and bottom.

[Jonathan Kirsch]

Thanks, Boyd. I know it's a user option, I just wanted some reassurance that if I selected the zoom (or fullscreen) 16:9 mode that I will get my original picture I shot, no resolution loss (scaled up) or cropping.

Jonathan

[Boyd Ostroff]

If a user selects the zoom option then it definitely will scale the image, as well as distorting and cropping it. The 4:3 option won't lose any resolution, but it will be distorted (everything will be too tall and thin). But there really isn't anything you can do about this when authoring a DVD.