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Old May 10th, 2002, 06:12 PM   #1
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Converting between 16:9 and 4:3 info

Hello,

I put up a few tutorials about working with 16:9 and 4:3.

It is my approach to working with both formats, combining the two aspect ratios as well as howe to letterbox your 16:9 footage. It revolves around using Adobe Premiere 6.0.

Hope someone finds it useful. Just go to my tutorials section* at:

http://home.attbi.com/~DVfilmmaker/

*Please note that I am still having trouble with attbi servers. If you get an error, hit refresh.
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Old May 10th, 2002, 11:48 PM   #2
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Nice site, and very useful, practical information. Thanks!

I had one question/comment: in your 16:9 section, you say that shooting 4:3 and then letterboxing it loses pixels. This makes sense. But, you say that shooting in 16:9 mode gives higher image quality. Doesn't the XL1/XL1S just discard pixels at the top and bottom of the CCD array, and so is really "faking" 16:9 mode?
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Old May 11th, 2002, 02:10 AM   #3
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In my understanding, from conducting several tests, the 16:9 provides a crsiper image than matting 4:3. I have not run across any numbers. I would love to find out the real numbers on this.

I think the difference lies in the 1.2 to .9 Pixel Aspect Ratio. When you convert 16:9 to 4:3 you end up with the same image size, but when you enlarge the 4:3 to 16:9 you will get a softer picture. This I know to be true from my own experiments.

To my eye, the 16:9 image is sharper when I reduce then 4:3 matted. This my be purely subjective without hard evidence.

I also take advantage of the fact that I have a 57" Sony HDTV. This is where the differences really become visible.

Anybody with more technical info is encouraged to write me. I would like to post the most up to date info I can.
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Old May 11th, 2002, 12:50 PM   #4
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I've been trying to pin this down, too. The most cogent theory that I've read says that, when you use the XL1(s)'s 16:9 mode, it's compressing the image after doing the in-camera masking of the image to 16:9. So, you're using the entire 25Mbit/s bandwidth for those pixels. If you shoot in 4:3 and mask in post, the camera's compressing the entire image, thus using less bandwidth per pixel. That would, logically, result in a slightly better image if you use the camera's 16:9 mode.

A related question: I have Mitsubishi HDTVs: a 63" and a 55" (or thereabouts). Both have three viewing modes: normal (where the tv puts gray vertical bars on each side of a 4:3 image), expand (where it stretches a 4:3 image horizontally to fill the screen, and makes anamorphic 16:9 material look correct) and zoom (which make a letterboxed movie fill the screen).

Does your HDTV have the same modes?

I currently shoot in 4:3 mode and letterbox in post, and use zoom mode to play on my HDTVs. The material comes out letterboxed on a regular 4:3 tv. This definitely pushes the camera's quality to the limit, and, on the big tvs, it looks ok...about the same as satellite broadcast. I'd like better quality, and so your solution is intriguing. Unfortunately, shooting in the camera's 16:9 mode means that I have to live with the dreaded black bar across the bottom (see the very lengthy thread under General Topics for a discussion of this), and I can see this in your screen shots, too. The black bar is there in 4:3 mode, too, and slightly larger, but letterboxing the material eliminates it. Of course, it doesn't show up on a tv, as it's outside the tv safe area, but it does show up on a computer monitor.
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Old May 11th, 2002, 01:08 PM   #5
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"Does your HDTV have the same modes? "

My Sony has 4 modes.
Normal - 4:3 with gray bars down the side
Full - This is ideal for original footage shot in 16:9 w/ 1.2 PAR. This is where the televisions will eventually go.
Zoom - Enlarges the entire image, cropping the sides and tops
Wide Zoom - This is ideal for viewing letterboxed images. From my understanding, it expands the image to the edges and performs a compression at the top and bottom - approx. where the black bars are.

"The black bar is there in 4:3 mode, too, and slightly larger, but letterboxing the material eliminates it. Of course, it doesn't show up on a tv, as it's outside the tv safe area, but it does show up on a computer monitor."

When you lettebox a 16:9 to a 4:9 ratio, there is no way around the black bars. It is the only way to maintain the PAR. However, if you don't letterbox, you can view the full screen image on a 16:9 monitor. One day when all the televisions are 16:9 (I guess about 5-10 years) this will be the way to go.
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Old May 11th, 2002, 01:42 PM   #6
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Sorry, I wasn't clear. The "black bar" that I was referring to is a fault in the XL1S that puts a 4-5 pixel slightly fuzzy-edged horizontal bar at the bottom of the frame. It's about 3-4 pixels in 16:9 mode. There's a lengthy discussion of the fault in the General Topics forum...you'll see it under my name, near the top of the forum listing.

The black bar doesn't show up on a tv, because it's outside the tv safe area. It shows up on a computer monitor. I can see it, or something like it, at the bottom of the screenshots on your site. Apparently, the XL1 has a similar problem, with vertical bars on each side of the frame.
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Old May 11th, 2002, 01:54 PM   #7
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I shoot with a new XL1s, and yes this is an issue at times. I'm waiting for a fix like the rest of you. I will say this though, when you do the conversion as I have mentioned on my site, it goes away dramtaically, but it is still there.
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Old May 12th, 2002, 04:53 AM   #8
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I have been doing some testing of resolution achieved with my PAL XL-1 in various modes (frame, 16:9 etc). My goal was to get anamorphic material as a result because I present on a 16:9 screen, so that changes things a bit - i actually want the pictures to look squashed rather than letterbox it to get higher bandwidth available for the image.
Anyway. The final outcome was that in fact, in terms of sharpness, it was better to shoot 4:3, then crop and scale up in post. I also compared different software to achieve the up-scaling, and it turns out Virtualdub delivers a much sharper image than Premiere, but both beat the upscaling algorithm used in the XL-1.
The article with pictures will be posted in the Articles section sometime this week.

HTH

Kai.
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Old May 12th, 2002, 11:35 AM   #9
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So you are saying that you find enlarging a 4:3 to 16:9 image is sharper? If I understand this correctly, my experiments prove just the opposite. I wonder if it has to do ith the difference between PAL and NTSC.
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Old May 13th, 2002, 07:42 AM   #10
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Bottom line: the XL-1 does a passable job at 16:9 but it's not the best you can do.
Images to illustrate all this will be up later this week, somewhere on the Watchdog...

Kai.
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Old May 13th, 2002, 07:44 AM   #11
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End of the week thereabouts. Canon USA has always recommended shooting 4x3 and converting to 16x9 in post however I have heard about others who feel that shooting in 16x9 is better. Shows to go you. Thanks Kai,
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Old May 13th, 2002, 01:52 PM   #12
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I am just providing information on my site that covers my experiments. As I have written in my tutorial, this is an option for you to try, that I have not see anywhere else.

I think the XL1s does more than a "passable" job with 16:9. If you need to work with both 16:9 and 4:3 this is, IMHO, a good place to start.
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