How does a PAL Sony camera get 576 lines? at DVinfo.net

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Sony VX2100 / PD170 / PDX10 Companion
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Old September 13th, 2005, 11:01 AM   #1
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How does a PAL Sony camera get 576 lines?

How does a PAL Sony camera get 576 lines when the specs say it only does 530, which is the same as the NTSC version. It seems to me like at least 46 of these lines must be interpolated.
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Old September 13th, 2005, 11:36 AM   #2
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be assured that all lines are here, but depends how you count.
real video signal include some lines usually not visible on screen.
NTSC is said 525 but most of programs are just using 480.
PAL is said 576 but 540 is closer to reality.
As we live in a computer era where power of 2 is the king, it is easier to build a device that works with 480 than 525 or 540 instead 576.
If you still works in an analog world, you can probably capture with the old format 768x576 while most of digital system rely on 720x576 or 720x540 for the optimized ones.
your remark about the number of lines applies to nunmber of point per lines too.
since we do not live anymore in a square world, the pixel count per line becomes very variable, since the same old screen we know can use 768, 720 or any number you like, just use a pixel ratio you like.
that way, Mr Sony can sell you an HDV camera that claims a resolution of 1920 pixel with a CCD that count only 960.
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Old September 13th, 2005, 12:32 PM   #3
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The quick answer is that the 530 line spec is the horizontal resolution of the VX2100/PD170. The 576 line spec refers to the vertical resolution. So it's sort of like asking "how can a 6 foot tall man fit through a 3' doorway".... in that case the 3' measurement refers to the width of the door :-)
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Old September 13th, 2005, 12:47 PM   #4
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530 points/line resolution is a really good DV camera.
I doubt you can really get this (except with HDV) in normal condition.
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Old September 13th, 2005, 01:21 PM   #5
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PAL most certainly is 576 lines Giroud. Just as Boyd says - this is the vertical resolution that ALL PAL camcorders - even that 1984 VHS(c) nasty, outputs.

PAL pictures are 576 x 720 and NTSC are 480 x 720. Those extra 96 lines are nice to have over here.

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Old September 13th, 2005, 01:50 PM   #6
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As i said, yes PAL is 576 like NTSC is 480.
but if you are not going full digital (from camera to display), there is chance that the 12% overscan eats the borders on a regular CRT TV.
Since most of us are more or less going digital up to the final tape (or DVD), we consider that all these lines are ours. (but are you still placing your title using the safe margin in your NLE isn't it?)
And the proof is that vertical resolution for digital format for NTSC is 480 while analog NTSC always been 525, so why should it be different for PAL ?
Real analog PAL is 625, capturable is 576, but i doubt you can count on more than 540. (ok it is still better than 480)
For NTSC people , PAL is better , because it gives more pixels and is closer to 24p there is no discussion here.
for the 530 points/line of DV, i doubt that a regular DV camera (that most of us are using) can firmly claim for this.
Probably a VX2000 , undoubtfully a Panny AGDVX100 or Canon Xl2, but these are high end prosumer.
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Old September 13th, 2005, 01:54 PM   #7
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Quote:
Originally Posted by Boyd Ostroff
The quick answer is that the 530 line spec is the horizontal resolution of the VX2100/PD170. The 576 line spec refers to the vertical resolution. So it's sort of like asking "how can a 6 foot tall man fit through a 3' doorway".... in that case the 3' measurement refers to the width of the door :-)
Are you sure? That would be even worse as 530 is even more short of 720 than it is of 576!
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Old September 13th, 2005, 02:13 PM   #8
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it looks bad but VHS was about 350 , s-vhs/hi8 was about 420 and DV is over 500.
a mathematical law says that to reproduce a signal a specific resolution (lets say 530) you need to sample at least twice higher (in that case 1060).
So 530 from 720 is a pretty good score.
see http://www.dataforth.com/catalog/pdf/an115.pdf
basically if you take a chart made only of vertical lines (one black-one white)
a shoot it in a way it fills your screen, you can say the resolution of the camera is reached when you start to see the black lines and not only a grey surface.

Logic would be that 720 pixel should show you 360 black lines alternating with 360 white line, thus a 720 point per line resolution.
we are far from this and this is for black and white video only, since DV is 4:2:0 (NTSC is 4:1:1 but it is almost the same) so your color image as only a 360x240 matrix of virtual pixel due to the way DV signal is compressed.

not so far from here you will find the following:
http://www.dvinfo.net/sony/reports/vx2k-db.htm
Picture Resolution - Playback tests conducted at DV.com showed the XL1 was able to reproduce 460 lines of horizontal resolution. The PD150 played back 500 lines of resolution

Last edited by Giroud Francois; September 13th, 2005 at 03:02 PM.
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Old September 13th, 2005, 02:14 PM   #9
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PAL is a 625 line format, of which 576 are used to store picture information. NTSC uses 486 of it's 525 lines for picture. (horizontal lines = vertical resolution)

Both are sampled at 720 pixels horizontally. Resolution, however, is declared as lines per picture height, so given that TV is a 4:3 aspect ratio, gives 540 lines (720 x 3/4 = 540). (vertical lines = horizontal resolution)

Ignore issues of overscan, as they just confuse matters :-) and overscan is typically the same, in percentage terms, for NTSC and PAL.

Graeme
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Old September 13th, 2005, 02:47 PM   #10
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Using the set-up codes in my Sony TV's remote I've dialled out all the overscan. You don't need it these days, and now I have all the expensive wide-angle coverage I've paid for. I see all 576 picture lines.

tom.
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Old September 13th, 2005, 02:58 PM   #11
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hey , give us the trick !
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Old September 13th, 2005, 03:46 PM   #12
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I suspect this is what Tom is refering to. It's really amazing what hidden abilities your remote control can access. But read and heed all the warnings on this web page. You could permanently damage your TV, so caveat emptor!

http://myweb.accessus.net/~090/how2adj.html#5

I've tried this on my Sony WEGA 4:3 TV's and you can adjust many things. However, on those sets I wasn't able to completely eliminate the overscan no matter what I did. I suppose this will vary with model.
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Old September 13th, 2005, 03:49 PM   #13
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Also, if you're really interested in these questions of resolutions, the following site goes into an incredible amount of detail. You'll need to set aside the better part of an evening to read and comprehend it though! ;-)

http://www.uwasa.fi/~f76998/video/conversion/
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Old September 13th, 2005, 03:56 PM   #14
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this one pretty good too
http://www.lafcpug.org/Tutorials/bas...ma_sample.html
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Old September 13th, 2005, 09:29 PM   #15
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OK, now I'm starting to understand. Boy was I under some misconceptions. Let's see if I've got this right:

NTSC is always 580 lines of vertical resolution. PAL is always 576 lines of vertical resolution. What varies from camera to camera within a format are the number of horizontal lines of resolution. There is a theoretical 720 lines of horizontal resolution in both NTSC and PAL. In actuality however, the ideal of 720 horizontal lines of resolution is never reached. The 530 that a Sony DV camera is supposed to get is high compared to other cameras. The DV format itself is limited to 500 lines.

Color resolution is a whole other story I understand, but PAL is superior there too.

Now I'm still curious, do standard DVDs made from film transfers use the full 720 x 480 lines of resolution or are there similar resolution compromises made with film transfer equipment?
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