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Old May 3rd, 2002, 03:44 PM   #1
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Fields (not the one in the country!!!)

I hear a lot about 'fields' on these boards but have no idea what they are or what they do?

Whats the difference between Upper and Lower fields?

What does it mean?

How are they used?

What are they used to do?

etc, etc, etc

Any Info would be appreciated.

All the best,

Ed Smith
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Old May 3rd, 2002, 04:33 PM   #2
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fields are a interlacing method used for motion, at least in my work
3d, DV, ect.

In my opinion it doesnt really matter wiether or not the upper or lower fields
start the render, as long as your working from scratch.

when rendering in fields it does what video cameras do when they capture footage, one frame will be the upper field (which will consist of only half the picture, percentage wise) and the next frame will have a lower field (with the other half of the picture.) thus gives you 60i NTSC 50i PAL, per second.

say you have shot footage on the XL1 in frame. now you bring that in to a
NLE program and do you magic, when done you have the option, to render fields or not. In this situation, it will take you 30p (progressive) frames from the XL1 and convert it to 60i (interlace). This usually works well with text motion, panning scenes, running scened, ect.

hope this helps!
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Old May 3rd, 2002, 04:54 PM   #3
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Its kanda like Interlaced and Deinterlaced?

I guess this might have solved my problem of jerky/ judder footage.

I recorded with out frame movie put into the computer interlaced so when I played back (through camera and viewed on TV) I got a judder/ jerky footage as the camera moved. I guess I need to deinterlace the footage, how is that done with in Premiere 6? or is there another way to do this?

So if I shot in Frame movie mode this would not happen if the footage is captured interlaced?

Cheers for the info redone,

All the best Ed
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Old May 3rd, 2002, 04:55 PM   #4
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I have a question. What about videogames that run at 60 images per second, but don't interlace? They just use one field updated 60 times a second. That wouldn't be 60i, so what would it be?
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Old May 3rd, 2002, 06:44 PM   #5
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well, if you want to deinterlace you can go to you r general settings>keyframe and rendering> and then turn on the fields,
select upper or lower first.

but i dont think thats you problem. are you dubbing back from the timeline
or outputting.???you might be dropping frames too, check up on thaty when you output.

as far as video games go, i think they send a signal of interlaced frame rate,
but not sure what rate...though i know when played on a monitor, it can be measured by refresh rate as well 60 or 75mz.
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Old May 3rd, 2002, 07:10 PM   #6
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What is interesting about videogames of old (new systems interlace) is that if you looked closely you could see the gaps where the other field would go (as thin black lines). There was no flicker, and you could record this onto videotape and it would retain the single field scan rate. Must be built into all TVs.
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Old May 5th, 2002, 11:30 AM   #7
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Just playing back from the timeline through the DV cable, through XL1 and then, onto the TV, that is when it jerks. So I thought that it might have something to do with interlaced/ deinterlaced - you are supposed to deinterlace when you use the slow-mo function - so I thought it I might have to do something like that to sort out the footage. So I deinterlaced the fottage, this time I lost the jerky footage but got blank screens for a couple of frames instead of the jerky effect.
I also exported the movie as an uncompressed AVI file and then converted that to MPEG, and I had no jerky effect (no frames were lost during this).
I guess that its got something to do with fields/ interlaced/ deinterlaced, then again I might be wrong?

All the best,

Ed
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Old May 11th, 2002, 07:25 PM   #8
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You can read up about fields at:

www.adamwilt.com

A great info site, I might add. NTSC contains a tad under 30 FPS, thats 60, 1/2 frames or 60 fields (odd and even, alternating).
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Old May 11th, 2002, 08:03 PM   #9
 
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On the contrary, the correct field order is VERY important when the images are decoded/reconstructed. If the wrong field is first, and if there is motion in the image, there will be a mis-registration of the fields, resulting in a blurry image. For NTSC and PAL, the standard is lower field first, AKA Field B. Inverted field order that results from starting with the wrong field first will also result in a jittery motion.

As a general rule of thumb....always interlace for TV display, always deinterlace (progressive) for computer monitor display. MPEG2 will run either interlaced or progressive. TV circuitry will always interlace progressive source, unless you're running an HDTV.
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Old May 12th, 2002, 09:31 PM   #10
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right,

say if you have video thats interlaced, in which has already been edited
and imported for re-editing, you should fallow the field order according to that video footage, usually in Premiere it would reveal the field order for each file. As for interlacing video from scratch then the defualt setting will suffice.

in general settings you can make sure your frame rate is 29.97 for timline playback, which can sometimes differ from output framerate. I had the jitter problem my harddrive wasnt supported by ultra DMA, this however became a
problem when capturing and outputting. Ed, maybe thats something you can check up on, thats what fixed my problem, i got a newer motherboard.
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Old May 13th, 2002, 11:04 AM   #11
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I finally overcame the Jerky problem and came across this solution, cheers to you guys:

Captured footage with normal movie mode needs to be de-interlaced to 'No fields', in order for the footage not to jerk when the camera has the slightest of moves on play back via fire wire.

This does not matter if you have captured in Movie Mode.

All the best,

Ed Smith
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