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WizCraker
02-25-2005, 03:40 AM
A college instructor was trying to convince our class that NTSC was broadcasted at 320 x 240, maybe in the B/W days in 1953.

I said it was around 720 x 486 and this is the reply I got.


D1 is NOT NTSC broadcast you can not take a 720X480 video strean and have it broadcast correctly. D1 is the the modern NTSC video format, used in DV decks and eventually DVD's and players. You don't usually have a 720x480 VCR (unless you have some high end equipment from JVC and such

I think he is getting from this:


Although VCD2.0 only supports video clips at a resolution of 352x240 (NTSC) or 352x288 (PAL),

This can't be right as every where I search it says it is 640x480 or greater depending if it is perception, square pixel, non square pixel, D1, D2. In all the docs from Lightwave, Digital Fusion, Ae, they all say 720 x 486 is standard.

Last time I sent my demo reel out I rendered 720x486 and it worked fine on my el cheapo VCR deck from walmart. I don't know what this guy is speaking about "High End Equipment."

Can anybody enlighten me on the correct format?

BeeVee
02-25-2005, 05:03 AM
The resolution he's quoting is a VGA one, and wasn't in existence before confusers, sorry, I mean computers. Indeed, no-one thought in pixel sizes then... There are some details on pixel sizes here (where you see line, you can pretty much susbtitute a vertical pixel count): http://www.williamson-labs.com/ntsc-fink.htm but it should be borne in mind that in its monochrome infancy, TV was a lot more wil and woolly than it became once standardised on a single colour standard (for NTSC).

B
PS. Another reason why NTSC couldn't possibly have been broadcast in 320x240 is pixel aspect ratio compared to frame aspect ratio. NTSC pixels have always been taller than they are wide, so an image at this resolution would go off the screen - 320x200 would fit better on an NTSC TV screen.

TSpyrison
02-25-2005, 05:27 AM
D1 is NOT NTSC broadcast you can not take a 720X480 video strean and have it broadcast correctly

Wow..

I guess the TV station that I work for has been doing it all wrong the 8 years I've been here. What is this guy an instructor of?

spec24
02-25-2005, 07:01 AM
that's college instructors for you. One of my instructors is convinced that a computer screen is only capable of displaying 72 DPI. Of course the term itself has no meaning on a computer screen really - it's a physical print size. He was actually trying to convince my poor naive class that a picture with a resolution of 800 x 600 at "72 dpi" displayed on a 10" screen at 1280x1024 would appear exactly the same size PHYSICALLY as it would on a 60" screen at 1280x1024!

marble_sheep
02-25-2005, 03:31 PM
Yeah, your instructor is a moron.... and you can tell him I said so! :p I have worked in broadcast for more than six years, and the only thing he is kind of right about is that T.V.'s aren't capable of showing 720x486 pixels. Depending on the T.V., it's closer to 640x480. That's why there are title-safe area and stuff. BUt.... he is completely whack if he thinks a T.V. can only show 320x240. But you most definitely can broadcast 720x480.

wulfie
02-25-2005, 10:24 PM
I am getting ready to do a lot of compositing with Mini DV which is 720 by 480. So should I be not using the D1 720x486 setting that LW uses? My camera man said I maybe I should use the custom settings and create 720 by 480 I will need to be tracking the camera movements etc. I need to get this right and you guys sound like you know what you are doing. Thanks very much.

Bev

SplineGod
02-26-2005, 12:18 AM
If you ask a computer guy what the resolution of his computer screen is he could give you a variety of answers but it would be in pixels.

As the same question to a TV engineer and he will give you the answer in nanoseconds.

Theres only approximate comparisions between computer and TV displays.
I would read this:
http://members.aol.com/ajaynejr/vidres.htm

VHS and SVHS are formats. VHS is limited to approximately 320 x 480 (interlaced video). SVHS is around 640 x 480 (interlaced). In reality the vertical resolution of a TV is locked to 525 scan lines. Horizontally it can vary. Again were talking apples and oranges - Digital vs Analog.

faulknermano
02-26-2005, 04:00 AM
excellent link and post, larry. thank you. :)

SplineGod
02-26-2005, 04:06 AM
Hey Lernie!
Well I remember years ago when the first video toaster came out. I did a lot of tech support for those things and I remember asking a TV engineer what the resolution of a particular monitor was and when he replied "oh its got 35 nanosecond pixels" I just KNEW I wasnt in Kansas anymore :)

marble_sheep
02-26-2005, 09:07 AM
VHS and SVHS are formats. VHS is limited to approximately 320 x 480 (interlaced video). SVHS is around 640 x 480 (interlaced). In reality the vertical resolution of a TV is locked to 525 scan lines. Horizontally it can vary. Again were talking apples and oranges - Digital vs Analog.

You are right about it being apples to oranges. But... since we are all digital artists, we have to approach things from the (relatively) limited and straightforward world of pixels.

If you want to be technical, the number you quoted (320) is actually closer to the mid-200's in most real-world situations. I think the number you arrived at was probably figured using the Kell Factor, which is an equation used to try and relate the analog world of video to the digital. There are many factors that can cause that number (320) to vary... since analog by definition is ever changing. Depending on synchronization of equipment, etc, that number can actually be as low as 200-something. If you were to print out a page that "showed" every pixel, i.e. a black-white checkerboard pattern with each square representing a pixel on a computer, then if you shot video of that page, the number of pixels you could see would depend mainly on whether the pixels were in sync with the scan lines of the camera. Other factors such as the format you are recording to, the type of cable you send the image across, even the dirtiness of the lens, can all cause that number to fluctuate. And actually... analog resolution us usually measured in MHz... the amount of cycles a given analog format is capable of producing, along with all the other factors (such as scan rate synchronization) work together (or against each other!) in regards to final perceived pixel output.

But... the original poster was asking about broadcast standards... not VHS. Broadcast equipment is very capable of taking a 720x480 image and making it analog. Trust me on this. A T.V. is very capable of accepting a 720x480 image... you just won't see all of it. What changes is the perceived resolution when it finally gets viewed again.... and this fluctuates constantly! So... if you are creating images for broadcast you want them to be a higher quality than they will probably be seen. So... that is why I said his instructor was wrong... he was trying to say what could be broadcast, not viewed... and 720x480 can most definitely be broadcast... the average viewer just won't be able to see all of those pixels at once. The information is still there, just not viewable all at the same time.

So, I stand by my original assertion that his prof is whack! :p

SplineGod
02-26-2005, 03:34 PM
Oh very true!
Broadcast standards really dont deal with resolutions or even image quality in general. They deal with electrical specifications which is why various TV shows can broadcast bad looking VHS tapes.

Studio cameras can send out a singnal thats higher resolution then 720x480 but as the signal is processed the resolution is decreased until its pretty low.

I remember someone saying that broadcast quality is whatever the engineer puts on the air :)

faulknermano
02-26-2005, 07:26 PM
I remember someone saying that broadcast quality is whatever the engineer puts on the air :)

we say the same thing over here. :D

MikeMD
02-27-2005, 02:47 AM
Actually professor is right ( off by a little bit ).

A broadcast signal displayed on TV can only show up to 330 horizontal lines, no matter what the tv is actually capable of, or what kind of signal you broadcast.

330 lines is max for broadcast tv display.

marble_sheep
02-27-2005, 10:59 AM
Hi Mike,

I agree with you that a typical broadcast signal is limited to approximately 330 due to the analog bandwidth limit of a traditional broadcast. And actually, that number can get reduced even further along the way. However... you are talking about lines of analog resolution based on an analog wavelength. Go back and read the original post... the prof is obviously confused because he is equating lines of resolution to pixel dimensions. True, a standard broadcast signal will drop resolution as lines or dots (or other details) fall between the cycles of the wavelength. However, you can most certainly broadcast a 720x480 pixel image. Pixels to analog lines... two completely different things... he is flat out wrong to say that you can't broadcast an image of that pixel resolution. It just won't look as detailed when it is finally viewed, and as it is converted into an analog waveform some information will be dropped.

SplineGod
02-27-2005, 04:44 PM
All very true. It can be pretty confusing. If anyone remembers those black and white test pattens that use to show up on TV early in the morning years ago it was to help adjust things. To figure out the resolution of TV screens a multburst pattern was generated that were vertical lines getting closer and closer together. The lines of resolution were how many of those lines could be resolved as individual lines before they mushed up determined that. So between the quality of the TV signal and the quality of the equipment creating the signal there was a lot of leeway.

It reminds me of a story I heard about the early days of lasers. There was not equipment to measure laser power at the time and so laser power was measure in 'Gillettes". So a 5 Gillette laser was one whos beam could burn thru 5 Gillette razers and so forth. :)

ChrisS
03-01-2005, 08:27 AM
All that wasted render time - I coulda been rendering at 320x240! ;)


I am getting ready to do a lot of compositing with Mini DV which is 720 by 480. So should I be not using the D1 720x486 setting that LW uses? My camera man said I maybe I should use the custom settings and create 720 by 480 I will need to be tracking the camera movements etc. I need to get this right and you guys sound like you know what you are doing. Thanks very much.

Bev

Yep, just use a custom setting of 720x480. The pixel aspect for a 1.33 frame aspect becomes .88-something, but I digress... the D1 .9 is just fine.