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TUTORIAL: Chromanator Misc: Using split fields for slow-mo

Posted: Thu, 22nd Jul 2004, 3:32pm

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Simon K Jones

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Chromanator Tutorials: Chromanator Misc

Using split fields for slow-motion

Most DV cameras capture interlaced footage. This means that each frame actually consists of two separate fields, each of which is half the resolution of the full frame. Interlacing was originally introduced because early television sets were not powerful enough to display an entire frame at once, so instead would show one field, then the next.

This can cause problems when editing on a computer, as both fields are displayed simultaneously, which can result in the tell-tale interlace banding:

Normally when working with interlaced footage in Chromanator, you would set up the project correctly (by ensuring that ‘progressive' is not ticked in the new project dialog), and the program would automatically split the fields into separate frames, enabling you to work on the footage without the banding problems:

The fields are then reinterlaced upon rendering.

Interlacing can also be put to good use when you want to use slow-motion. PAL runs at 25fps, but each frame has two fields. If these fields are separated it doubles the number of frames, halving the speed of the clip, as each field is shown as an individual frame.

A clip's fields can be permanently separated in Chromanator.

  • First start a new project but ensure that it is a progressive project setup.

Now import your interlaced footage. From the media browser, select the clip and choose ‘Properties' from its menu.

  • Change the Scan Method to ‘Split Field (Even)' and click OK.
  • Note that some cameras interlace footage differently, in which case you may need to select ‘ Split Field (Odd)' to avoid strange playback.

Each field will now be treated as a separate frame. However, as you are working in a progressive project setup, the fields will not be reinterlaced when you render.

This means you can render the clip as a half-speed version of the original, which can then be adjusted as required, either in Chromanator or your editing program.

Download an example clip.

Posted: Thu, 22nd Jul 2004, 3:41pm

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CoolKabe

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Whoa! Dang, that's awesome! I'm going to try that right now... MUAHAHAHAHAHAHA! razz

biggrin

-Adam twisted

EDIT: I just tried it, it works quite nicely, thanks Tarn!
Posted: Fri, 23rd Jul 2004, 7:02am

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Redhawksrymmer

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Thx Tarn, well written as always. And it sure does work.
Posted: Fri, 23rd Jul 2004, 4:57pm

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Ryan

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Wow, that's great.

Oh, and congradulations on having over 4000 force points.
Posted: Mon, 26th Jul 2004, 1:43am

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Evman

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isn't this more easily acceived by just adjusting the speed of a clip in your NLE?
Posted: Wed, 28th Jul 2004, 2:29am

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Ryan

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It wont be smooth if you do that.
Posted: Wed, 28th Jul 2004, 2:30pm

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padawanNick

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Depends on your NLE.
Setting speed to 50% on some NLE's will just "double-up" frames (display the same frame twice) or show a single, deinterlaced field for two frames before moving onto the same field from the next frame.

I know Media Studio Pro produces the same result as this tutorial just by setting speed to 50%. I think Final Cut Pro & Vegas do as well, but I don't know about Premiere since AE has all kinds of features for doing this and Adobe would much rather see people spend money on both AE and Premiere. razz

Cool tutorial, though.

Have fun.
Posted: Wed, 28th Jul 2004, 3:09pm

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TheRenegade

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Thats Sweet.










The Renegade
Posted: Mon, 2nd Aug 2004, 10:23am

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Simon K Jones

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Some NLEs do this effectively, while others can give unpredictable results. The main benefit is that you can use this to easily split the fields permanently, and you'll know exactly what is happening.