OAR, Original Aspect Ratio - Black Bars and Burn-in

Richard · Post by **Richard** » Tue Apr 27, 2004 10:24 am

This is from the TIPS list for subscribers only.

Note that all HDTV delivery except Showtime and possibly Pay per View are formatting the movie to fit your screen at this time. This only effects movies wider than 1.85 such as the Star Wars series at 2.35. Nearly half of the movies made use 2.35.

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There was a post stating that HDTV is always 16:9.

16:9 is a 1.79 ratio and this ratio doesn't exist in the catalog of available formats. It is only due to HDTV that this will become an actual format. How they came up with 16:9 was by averaging all available formats.

OAR means original aspect ratio. When displaying the various formats correctly on a 1.79 screen you will get black bars somewhere, black bars on the top and bottom varying in size or black bars on the left and right varying in size. That is why it would still be HDTV even though there are black bars. The only formats that "appear" compatible with no black bars is 1.85 and 1.75.

OAR over the years:
1.33=4:3
1.37
1.5
1.66
1.75
1.85
2.21
2.35
2.39
2.52
2.55
2.59
2.66
2.76

I would hope that we can educate users that filling out the screen is to the detriment of the artist and our experience of their work. Black bars somewhere will be a part of our lives for many years to come. Thanks and kudos to showtime for their support of OAR presentation. Scowls and disappointment to HBO for being a whimp and filling out the screen for ALL movies instead of providing a quick 2 minute educational commercial about OAR. I have found if people are shown and educated they will accept this.

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:38 pm

This is an excellent education in aspect ratios. Enjoy.

Thanks to Bobby C, one of our posters here at the Forum and the TIPS List.

http://www.thedigitalbits.com/articles/ ... orama.html

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:38 pm

And some more from a TIPS List poster

http://www.jeremymoore.com/AdobePremiere/PAR_Displays/

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:40 pm

What does it mean when a DVD states it is Enhanced for Widescreen TVs? Is it OAR or not? If the aspect ratio on the DVD says 1:85:1, is it stretched to fit on a 16:9 TV which is actually 1:78:1. Or are there bars on the top and bottom that are so small they can not be noticed?

DM145

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:40 pm

What does it mean when a DVD states it is Enhanced for Widescreen TVs?

It should mean that the signal has been encoded to provide higher bandwidth for OAR movies.

LETTERBOX or WIDESCREEN on any display

In a 4:3 world a film mastered for OAR presentation will have black bars on the top and bottom and is normally called "widescreen" and "letterbox". If it is 1.85 then there are small ones. If it is 2.35 there are large ones and the actual picture ends up being a small strip in the middle of the display. Some movies for DVD are still mastered this way and they should not say "enhanced" on the box. If you have setup the DVD player for the correct display these movies will appear correct on 4:3 display but will appear squeezed on a 16:9 display forcing you to use the format control to expand the picture vertically only (stretch and expand are common terms). This kind of mastering represents the worst way to experience a movie because you are using the bit-stream bandwidth to also encode the black bars or put another way you are applying the bandwidth to the full 4:3 picture area. The picture quality of these movies is fairly equal regardless of the display.

ENHANCED

Due to HDTV and the 16:9 ratio, which is 1.79, 4:3 mastering is a waste so most movies are mastered using a process called "enhanced for 16:9 displays" and that means they have applied all that bandwidth to just a 1.79 area which improves picture quality dramatically if you have a HDTV or 16:9 display.

ENHANCED on a 4:3 analog display

While it would make sense that an enhanced DVD looks better no matter what display you use the reality is if you have a 4:3 NTSC display you will not get the full benefits unless you set the player for 16:9 which will geometrically distort the picture due to the stretching effect of this mastering process. So for these folks enhanced just doesn't mean a whole lot. I will speculate that the reason it looks worse is because the signal must be scaled for a 4:3 display.

ENHANCED on 4:3 HDTV display

If you have setup the DVD player for a 16:9 display these movies will appear stretched forcing you to use the format control to compress the picture vertically only (compress and squeeze are common terms). In most cases this will create grey bars in the area that is beyond 16:9 just like an HD 1080I signal does. With a 1.85 movie all you will have is the grey bars. With a 2.35 movie you will also have small black bars next to the grey bars. This is normal for 4:3 displays.

ENHANCED on 16:9 HDTV display

If you have setup the DVD player for a 16:9 display these movies will appear correct at all times provided you are using the correct format. With a 1.85 the screen will be filled out because the difference between 1.85 and 1.79 is too small to show black bars on the top and bottom due to overscan. With a 2.35 movie you will have small black bars on the top and bottom.

>>Is it OAR or not?

It usually is what the director intended and that is what OAR is all about. For the nit-picky, T2 was filmed with a 1.85 ratio but has always been released as 1.33 (4:3) or 2.35 so no matter which version you watch something is being cropped.

>If the aspect ratio on the DVD says 1:85:1, is it stretched to fit on a 16:9 TV which is actually 1:78:1. Or are there bars on the top and bottom that are so small they can not be noticed?

Only those people with a 0-2% overscan would notice a small sliver of black on the top and bottom if they were looking for it. It is rare that one would have such a display.

Richard F. Fisher

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:41 pm

How many hours of a consistant picture does it take before burn in takes place?

Andy

HDTV Forum · Post by **HDTV Forum** » Wed May 19, 2004 10:52 pm

Only CRT and plasma based displays are susceptible to burn-in.

Burn in is caused when a specific area of the picture contains an image which either never goes away such as station logos or different in content such as stock market tickers or black/gray bars. No matter what your source is you are susceptible. There are ways to reduce this.

The short explanation of this problem is that your TV adjustments were setup by the manufacturer to make you buy the TV not supply you with a reference picture. You HAVE to adjust the controls to make it look normal. Purchase the Avia DVD and learn all about TV pictures while setting the controls for the best performance.

The back of most owners manuals now have disclaimers that phosphor aging, burn-in, will not be covered by the warranty. This is due mostly to the black or grey bars but it also happens with regular TV content. Station logos that are not see through or opaque can burn-in. News programs with their static graphics can burn-in. Stock tickers constantly running across the bottom will cause burn-in. Anything that does not evenly use the different parts of the display picture can burn-in. Most manuals express this by telling you to evenly mix 2.35 DVD

HDTV Forum · Post by **HDTV Forum** » Tue May 25, 2004 11:21 pm

Grey bars vs Black bars

When I watch widescreen material-(HDTV or DVD) on my 4:3 direct T.V. I can choose compression mode-Black bars or letterbox mode-Grey bars. I understand that grey bars are less damaging on the picture tube then black bars because the grey bars constitute lines of resolution that are suppose to use the tube more evenly. This would diminish the burn-in effect. Do the grey bars really diminish the burn-in effect and if so how much in term of percentage in comparision to the black bars.

Ronny70

HDTV Forum · Post by **HDTV Forum** » Tue May 25, 2004 11:22 pm

In what I have read about 'burn in' there is no difference having gray or black bars. Even if there was an option of having white bars 'burn in' would still be a factor on your screen. This is so because the color really has nothing to do with it. Burn in occurs when there is uneven wear to the lenses...whenever a still image is plastered on the lenses instead of constantly changing images. Think of a rubbing a pencil against paper while never rotating...you will eventually get a nice round side and a flat one that rubs on the paper...very simplistic example.

Anonymous

HDTV Forum · Post by **HDTV Forum** » Tue May 25, 2004 11:23 pm

Burn-in is uneven wear of the phosphors and you can get it from lots of things besides gray/black bars and it has been around for decades. Whether gray or black the first sign will be a defined line where the picture and bars meet. Some manufactures use orbitting or side to side shifting to prevent the line. Even then, eventually the bar areas will drop or increase in brightness compared to the 4:3 area. Direct view CRT is somewhat susceptible while plasma and projection CRT are very susceptible. Light engine products such as DLP, LCoS and LCD do not suffer from this.

Mix your images and you will be just fine.

Richard F. Fisher