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Fields per second vs. Frames per second

 
 
Radium
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      10-21-2006, 10:43 PM
Hi:

PAL video system uses 50 fields per second and 25 frames per second.
Whats the difference between "field" and "frame"?


Thanks,

Radium

 
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Henry J Cobb
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      10-21-2006, 10:57 PM
Radium wrote:
> Hi:
>
> PAL video system uses 50 fields per second and 25 frames per second.
> Whats the difference between "field" and "frame"?


A field is where the electron gun sweeps all the way from the top to the
bottom of the screen.

A frame is a complete picture of scan lines from the top to the bottom
of the screen.

The difference is that PAL (and NTSC), take two fields to draw one frame
because each field shows alternating scanlines on the screen.

You can see this by slow stepping video that has rapid side to side motion.

The alternative is to draw the entire picture with each field (at one
field per frame), which is called progressive scan.

http://en.wikipedia.org/wiki/Progressive_scan

-HJC
 
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Richard Crowley
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      10-21-2006, 11:28 PM
"Radium" wrote ...
> PAL video system uses 50 fields per second and 25 frames per second.
> Whats the difference between "field" and "frame"?


The traditional popular TV standards (NTSC, PAL)
are interlaced and use 2 fields per frame. Each field
is composed of every-OTHER line. For example
one field has all the odd-numbered lines, and the next
has all the even-numbered lines. Curiously enough
they are commonly refered to as the "Even Field"
and the "Odd Field".
 
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Jukka Aho
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      10-22-2006, 06:32 PM
Radium wrote:

> PAL video system uses 50 fields per second and 25 frames per second.
> Whats the difference between "field" and "frame"?


See <http://lurkertech.com/lg/fields/fields.html> and then the sample
pictures here:
<http://www.100fps.com/>. (Examine especially the three pictures below
the words "Here is an example of what your digital camcorder does".)

--
znark

 
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John Popelish
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      10-22-2006, 06:46 PM
Jukka Aho wrote:
> Radium wrote:
>
>> PAL video system uses 50 fields per second and 25 frames per second.
>> Whats the difference between "field" and "frame"?

>
>
> See <http://lurkertech.com/lg/fields/fields.html> and then the sample
> pictures here:
> <http://www.100fps.com/>. (Examine especially the three pictures below
> the words "Here is an example of what your digital camcorder does".)
>

One field delivers the odd lines and the other delivers the
even lines of the same frame.
 
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Richard Crowley
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      10-22-2006, 07:28 PM
"Jamie" wrote...
> sounds like the Robot Color modes used for Slow scan TV.


Even/Odd field interlace has been the way it was done
for NTSC/PAL/SECAM since day one here on our planet.
Nice to know you have more advanced technology on your
planet. Where are you writing from?
 
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Michael A. Terrell
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      10-22-2006, 07:49 PM
Richard Crowley wrote:
>
> "Jamie" wrote...
> > sounds like the Robot Color modes used for Slow scan TV.

>
> Even/Odd field interlace has been the way it was done
> for NTSC/PAL/SECAM since day one here on our planet.
> Nice to know you have more advanced technology on your
> planet. Where are you writing from?



One where they can't set their clocks.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
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Jukka Aho
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      10-22-2006, 08:09 PM
John Popelish wrote:

> One field delivers the odd lines and the other delivers the
> even lines of the same frame.


That description may lead one astray, since in interlaced video, the
fields are not only displayed but also acquired at different instants in
time. A "video frame" is not a frame in the same sense as a film frame
is.

--
znark

 
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Michael A. Terrell
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      10-22-2006, 09:37 PM
Jukka Aho wrote:
>
> John Popelish wrote:
>
> > One field delivers the odd lines and the other delivers the
> > even lines of the same frame.

>
> That description may lead one astray, since in interlaced video, the
> fields are not only displayed but also acquired at different instants in
> time. A "video frame" is not a frame in the same sense as a film frame
> is.
>
> --
> znark



That is why they are called fields, not frames. If you can't
understand the difference, its time to crack the books, or find another
job.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
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Michael A. Terrell
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      10-22-2006, 09:40 PM
Jamie wrote:
>
> Michael A. Terrell wrote:
>
> > Richard Crowley wrote:
> >
> >>"Jamie" wrote...
> >>
> >>> sounds like the Robot Color modes used for Slow scan TV.
> >>
> >>Even/Odd field interlace has been the way it was done
> >>for NTSC/PAL/SECAM since day one here on our planet.
> >>Nice to know you have more advanced technology on your
> >>planet. Where are you writing from?

> >
> >
> >
> > One where they can't set their clocks.
> >
> >

> and what is wrong with my clock?, i just checked
> www.time.org, its with in 30 secs..



It must be set for the wrong tinme zone. Look at your posting
times. People reply to your messages BEFORE you post them.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
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