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#1 Latifian

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Posted 08 November 2005 - 02:16 PM

hi,friends[indent=1]

what is the necessity of progresive scan away field scan?

thank

Edited by latifian, 08 November 2005 - 02:18 PM.

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#2 David Mullen ASC

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Posted 08 November 2005 - 02:19 PM

hi,friends[indent=1]

what is the necessity of progresive scan away field scan

thank

I'm not sure I understand the question. Are you asking what progressive-scan capture is? Or what Sony's PsF format is (Progressive Segmented Frame)?
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#3 Latifian

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Posted 08 November 2005 - 03:26 PM

I know the picture in videography is maked by field & each field is scaned in diffrent time and any two field includ one frame(listening)so i heared in p mode all the frame is scaned in one moment.
Is this meaning one sec picture including 50/60 field or 25/30 p?
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#4 David Mullen ASC

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Posted 08 November 2005 - 09:12 PM

I know the picture in videography is maked by field & each field is scaned in diffrent time and any two field includ one frame(listening)so i heared in p mode all the frame is scaned in one moment.
Is this meaning one sec picture including 50/60 field or 25/30 p?


I still don't understand your question, especially that last sentence. But I'll try...

With interlaced-scan capture, each field is captured sequentially, and two fields are used to build one frame of video.

With progressive-scan capture, an entire frame is captured, although it will often THEN be broken up into fields for tape storage, sometimes with a 3:2 pulldown added (like when trying to store 24P capture as 60i video.)

Common interlaced-scan rates are 50i (PAL) and 60i (NTSC).

Common progressive-scan rates are 24P, 25P, 30P, although some cameras offer 60P and some offer many frame rates. In standard def cameras, progressive-scan capture is often stored in 50i or 60i, depending on if it is a PAL or NTSC camera. So 25P capture would be broken up would be stored as two fields per frame to create 50i.
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#5 Latifian

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Posted 09 November 2005 - 04:51 PM

Hi mr mullen

thank for your written

But my source question is this:
When the interlaced-scan is exist, why is the progresive-scan designed?what is the result of that?
I am very happy because to be able to use little from your knowledge. :rolleyes:
m-latifian[b]
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#6 David Mullen ASC

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Posted 09 November 2005 - 05:13 PM

Well, obviously progressive-scan exists for people who don't like the look of interlaced-scan.

When shooting at 60i, for example, you have motion sampled 60 times per second, usually at 1/60th of a second per field -- i.e. no shutter -- so there are no temporal gaps between the motion samples. So the high sampling rate and lack of gaps gives the motion a hyper-fluid "live" feeling, unlike the strobey look of 24P or film shot at 24 fps, where you have only 24 motion samples per second, usually with the shutter closed 50% of the time.

But interlaced-scan capture means that when the two fields are combined into one frame, you get a sawtooth edge to moving objects since half their scan lines exist from one field and the other half from the other field captured after the first. You also lose some vertical resolution with moving objects or shots because of this.

So hyper-smooth motion with no temporal gaps (unless a shorter shutter speed is used) combined with interlaced-scan artifacts give interlaced-scan a certain look that people associate with classic video.

Progressive scan shot at traditional film frame rates has more of a film look to its motion.
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