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HD telecine: 25p vs 50i


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#1 Maurizio Zappettini

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Posted 04 March 2010 - 02:58 PM

Hello

I've just finished to shoot a Super16 music video. Yesterday we telecined the whole footage to HDcam SR with a Spirit HD telecine. The footage will then be ingested for editing, vfx etc.

When we were ready to layoff the footage to HDcam SR once the grade was completed, I have been asked by the operator whether to layoff it in 50i or 25p (I'm in Europe). I was not sure about what to do, so I asked him which format he was suggesting and he said 50i. So we did 50i.

Today I started to think whether the 50i layoff could make the camera pans and general motion feeling more video, but I really don't want this to happen. Unfortunately I haven't had the chance to watch the footage on HDcam SR yet.

Does anyone know whether laying off at 50i could have taken away that beautiful film feeling in the motion and camera movements?

Many thanks

Maurizio
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#2 Alex Zustra

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Posted 04 March 2010 - 03:45 PM

Generally the progressive formats imitate film more closely since film obviously isn't interlaced. I'm thinking though, My television only does interlaced and it doesn't seem to have a noticeable effect on films, but maybe that's just because that's all I see. Also someone correct me if I'm wrong, but interlacing leads to a reduction in apparent contrast because the brain has to composite the interlaced lines.
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#3 John Sprung

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Posted 04 March 2010 - 04:10 PM

Since you're coming from 25 fps film, the only difference between 25p and 50i is that 50i is filtered to prevent interline flicker. You can still reconstruct the original film frames, they're just softened a tiny bit to get under the lower Nyquist limit of interlace.




-- J.S.
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#4 Eugene Lehnert

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Posted 13 May 2010 - 11:17 AM

What is the "Nyquist limit of interlace?"

I get 50i tapes with a 2:2 cadence that I slow to 23.98 via the deck all the time.

Thanks.
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#5 John Sprung

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Posted 14 May 2010 - 11:55 PM

What is the "Nyquist limit of interlace?"


In PAL, the equivalent of about 374 lines. The commonly accepted cheat is to soften interlaced material to about 65% of the equivalent progressive resolution. 576 x 0.65 = 374.4. To absolutely prevent any flicker, it would have to be 50%, which would have gained us nothing back it the analog days.



-- J.S.
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