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General discussion

Understanding Aspect Ratios and Screen Resolutions...

Jul 18, 2005 7:54AM PDT

Hello Everyone,

I thought I might make a quick post as this question has come up a few times and thought if might be worth its own discussion.

Aspect ratios and screen resolutions are very confusing and most people have not even taken the time to really understand them. There are so many different screen resolutions and aspect ratios out there it is hard to go through every one but for sake of simplicity I will show you what they basically mean and what you really need to be concerned with.

I actually just finished researching this topic in depth and am still a little dazed because these two topics actually crossover between the computer world and home electronics, with different meanings.

Here goes.

4:3 (pernounced 4 by 3) has been the standard for CRT TV's for over 50 years. 4:3 stands for 3 units high by 4 units wide when you look at your screen. Now if you divide 4 by three you get a integer of 1.33 to 1. So you can describe the aspect ratio of old CRTs in two ways 4:3 (ratio) or 1.33 (integer).

16:9 is the standard for HDTV. Again, if you divide 16 by 9 you will have an aspect ratio of 1.78.

The standard for WideScreen is 1.85 16.70:9
The standard for Anamorphic WideScreen (also know as CinemaScope)is 2.35. I was never able to locate the exact ratio for this screen shape. My assumption is that it is 21.19:9.

That said, how does the screen resolution fit into the above aspect ratios above?
When speaking of screen resolutions, a standard computer screen equivilent to the standard 4:3 CRT TV has a resolutions of 640x480.

Most displays use a square pixel size which means the display has more vertical columns than horizontal rows to complete a 4:3 or 16:9 image. Using a square pixel we can calculate how many vertical columns must be used for every horizontal line to create the proper image size:

4:3 display = 1.33 pixels high for every 1 pixel wide
16:9 display = 1.77 pixels high for every 1 pixel wide

Not all displays use a square pixel. Most newer displays use a slightly rectangular pixel and use interpolation, aliasing, or scaling to provide the illusion of a higher resolution square pixel display. Some of the 16:9 displays have a physical resolution of 1024 columns by 1024 rows because they use a 1.77mm horizontal x 1mm vertical pixel size.

The actual screen resolutions for your different displays are as follows:

480i - The picture is 704x480 - (60/2 interlaced frames per second)= 30 complete frames per second.

480p - The picture is 704x480 - 60 complete frames per second.

720p - The picture is 1280x720 - 60 complete frames per second.

1080i - The picture is 1920x1080 - (60/2 interlaced frames per second)= 30 complete frames per second.

# 1080p - The picture is 1920x1080 - 60 complete frames per second.

So in order for Sony and others to create a display with a resolution of 1024 x 1024 to be capable of displaying a 1080i (interlaced) image would require scaling and altering the image to fit the screen.

Until I am able to contact Sony and a few other manfacturers tech support dept for a more definitive answer (if they will give it) on how these displays are outputting 1080i, I hope this helps you with your questions.

Take Care,

Shawn Mosqueda
WireSmart LLC

If you would like to contact me, click on the profile link below.

Discussion is locked

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Great Post...Thanks Very Much
Jul 18, 2005 9:30AM PDT

I suspect there are more than a few here who appreciate your clear, lucid explanation of this whole thing.

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thanks!
Jul 19, 2005 9:08AM PDT

this has always frustrated me...why, why, why didn't they just make HDTVs standard widescreen instead of 16:9? but, thanks for the info.

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Nah....
Jul 19, 2005 9:12AM PDT

...As 16:9 much more closely aproximates the normal range of human vision (and has been used for moves from day one), the better question is what were they thinking when they first made the "regular" 4:3 sets.

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round tubes !
Jul 19, 2005 9:20AM PDT

some of the first crt tubes had a round face and a square picture appeared on the front with the edges masked of with paint. Why ? Mainly due to the fact that a vacuum is inside a crt and the rounded off tube was less likely to implode.

this is why a curved face picture tube set is lighter than a flat screen crt.

great answer re aspect ratios Shawn.

grim

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Look Again
Jul 19, 2005 12:22PM PDT

Before Cinemascope, most movies were shot in a 4:3 aspect ratio. That is why when TV was invented in 1929 and then demonstrated at the 1936 Worlds Fair, it had an aspect ratio to match what was then used in the movies.

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(NT) (NT) cool...more insight into why its that way!
Jul 19, 2005 1:50PM PDT
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Understanding Aspect Ratios and Screen Resolutions
Jul 20, 2005 7:30AM PDT

You did a very good on job the digital specs !!!!!

"When speaking of screen resolutions, a standard computer screen equivilent to the standard 4:3 CRT TV has a resolutions of 640x480."

There is one area that gets does get confusing when we talk about analog TV, since this is analog and every thing else is digital it is sometimes hard to compare the two. (apples to oranges)
If we were to put NTSC 525 interlaced lines in to computer terms it would be 320x240. What??? Sad, but true!! In computers this was called EGA, Commodore 64 anyone? Remember this was desinged back in the late 30s.
This is why DVDs look SO MUCH better on a computer or a DHTV monitor.
The way analog TVs are rated for picture quality is hard to translate over to digital also.
Anybody remember the term "lines of horizontal resolution" for rating the picture quality of analog cameras, TVs and VCRs??? This system of rating caused a lot of confusion back in the early 1980s when VCRs became popular. John

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: Understanding Aspect Ratios and Screen Resolutions..
Jul 20, 2005 7:45AM PDT

4:3 display = 1.33 pixels high for every 1 pixel wide
16:9 display = 1.77 pixels high for every 1 pixel wide

One little question here?? Maybe you meant this??
4:3 display= 1.33 pixels wide for every 1 pixel high
16:9 display= 1.77 pixele wide for every 1 pixel high

This tech stuff is sooo much fun keeping it all straight.
Sometimes I think about getting job where I only have to remember one thing. Like laying sod, just keep the green side up. John

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Thank you....
Jul 20, 2005 8:56AM PDT

John,

Good catch. These ratios vs screen resolutions are everywhere and it seems everyone has something different. It took along time to sift through everything and find the recurring numbers to finally find something one could feel good about giving as an absolute!!

When I was done my brain felt like mush!! LOL. Even now I have to refer back to my notes for clarification. IT'S NUTS!

I haven't been on the forums long, but I thought this was a question that has been repeated. I think we may need to bring it back to the top once in awhile. Your other link on CNET was very helpful too.

It seems alot of "experts" confuse SDTV with EDTV. I tell you, having this here sure saves some poor sap a ton of research, confusion and brain freeze (not as in cold, as in I can no longer process thoughts!).

Take Care,

Happy

Shawn Mosqueda

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It seems alot of "experts" confuse SDTV with EDTV
Jul 22, 2005 12:42AM PDT

This is true, SDTV label makes it sound like it is a digital format of some kind when it's not. So I call it standard NTSC analog TV, takes a few more words to say but but clears up a lot of confusion.
Going back to VHS/Beta wars there was similar confusion over tech terms and there wasn'e as many as there is now.
The problem is most store sales men are trained on how to sell monster cable, not on what the tech terams mean. The Sears Tv Guy is the excption. John

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welcome to my world
Jul 21, 2005 10:20AM PDT

keeping everything straight is a hard job to do. Trying to finishing my senior year in college and stay on top of the DTV world is difficult. Esp when every other place in town has idiots that confuse everyone and I have to work backwards just to get people in the right direction again and then explain some of the finer details. More power to ya for keeping up with all the harder details of hdtv

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We need more people like you...
Jul 21, 2005 3:04PM PDT

Hello,

I am in whole hearted agreement with you. There is more than enough confusion in this Tech world without salespeople with enough knowledge to make them dangerous giving ill advise. Drives Me NUTS!

The other one that drives me nuts are the builders out there that are still wiring homes the same way they have for 50 years! They just don't get it. We live in a technology age. Wiring new homes needs to be ready for networking computers, audio/video distribution (not daisy chained but actually home run to one or two media panel boxes), surround sound and video monitoring!

Anyway, nuff said. Keep up the good work.

Take Care,

Shawn Mosqueda
WireSmart LLC

If you would like to contact me, click on the profile link below.

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(NT) (NT) Thought I might bring this to the top for new readers.
Aug 3, 2005 3:09PM PDT