Converting odd framerates

[Walter Soyka]

By default, Premiere Pro duplicates (or skips) frames to match framerates. You can set a clip to frame blend [link] instead (right-click it and choose “Frame Blend”). This will create new intermediate frames by blending (I think via averaging, or a weighted dissolve) one frame over the other.

To figure out how the frames are duplicated, we can do a little math.

Output is 24 fps, Regular 8 is 16 fps. 24 – 16 = 8, so we have to make up 8 frames over 16, or 8/16 = 1/2. Every other clip is duplicated.

Output is 24 fps, Super 8 is 18 fps. 24 – 18 = 6, so we have to make up 6 frames over 18, or 6/18 = 1/3. Every third frame is duplicated.

If you step through your footage frame by frame in Premiere, you should see this is true.

Leaving frame blending off will give a sharper image with more stuttery motion. Turning frame blending on will give a softer image with smoother motion.

You can get a little fancier with 1080i60 output and custom pulldowns via a free tool called Avisynth. 18p to 60i is a 4:3:3 pulldown. 16p to 60i is usually reconformed down to 15p and then simply frame-doubled.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events

[Scott Allen]

So, it sounds like if I’m more concerned about sharpness of the frames, I go with the default frame-duplicating (in this case) – but if I’m more concerned about the “flow” of motion, I go with the frame-blending.

[Walter Soyka] “You can get a little fancier with 1080i60 output and custom pulldowns via a free tool called Avisynth. 18p to 60i is a 4:3:3 pulldown. 16p to 60i is usually reconformed down to 15p and then simply frame-doubled.”

How does that tend to affect the look of it as opposed to the less-fancy ways?

Thanks for the quick response,
Scott Allen
sallen@mailbox.sc.edu
University of South Carolina
Moving Image Research Collections

[Walter Soyka]

[Scott Allen] “So, it sounds like if I’m more concerned about sharpness of the frames, I go with the default frame-duplicating (in this case) – but if I’m more concerned about the “flow” of motion, I go with the frame-blending.”

I’d think people would tolerate a little bit of stutter really well with old home movies: it doens’t look like a technical flaw, it looks like nostalgia.

I’d be inclined to stay away from frame blending myself. Having it off by default is a good thing.

[Scott Allen] “How does that tend to affect the look of it as opposed to the less-fancy ways?”

Comparable to 3:2 pulldown for 24p to 60i.

Wikipedia has good background information on telecine pulldown [link], including information on other pulldown patterns.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events

[Robert Bracken]

How do I learn more about pull down? Where can I see some examples?

[Walter Soyka]

[Robert Bracken] “How do I learn more about pull down?”

The Wikipedia’s article on telecine has a great explanation of pulldown [link] — the process by which progressive frames from one frame rate are converted to interlaced fields of a different frame rate.

If you have specific questions, I’d be happy to try to answer.

[Robert Bracken] “Where can I see some examples?”

Nearly every film you’ve ever watched on a standard definition television had 3:2 pulldown applied.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events