The Mysterious Case of the 'Scale Motion Effects Proportionally' Setting

[PaulMurphy]

Listen up, folks.

I've been prowling the dark alleyways of Premiere Pro for decades, dodging bugs and navigating the labyrinth of settings like a grizzled gumshoe. But today, I stumbled upon a real head-scratcher: 'Scale motion effects proportionally when changing frame size.' Never needed it in the past, but today, curiosity got the better of me.

Here's the skinny. I figured if I change the frame size of a sequence—let’s say from 1080p down to 720p—and this box is ticked, the Motion settings of each clip should adjust proportionally. Simple, right? But when I put it to the test, nada. No change in the Motion settings, whether this setting was on or off. That’s when I knew I had a real mystery on my hands.

I went snooping around Adobe’s Premiere Pro User Guide, and the Change Sequence Settings page seemed to throw some light on the matter, but not much:

"Allows the user to scale the motion effect while changing sequences. A standard film workflow involves black bars on the top and bottom sequences. These black bars display the project data like timecode or clip name. You can alter the sequence without damaging the clip when this information isn't required."

The first sentence seemed to back up my hunch. But then they start talking about black bars and project data. What's that got to do with Motion effects? And this bit about "damaging the clip"? Makes about as much sense as a screen door on a submarine.

I knew I'd have to dig deeper, so I traced this setting all the way back to its oh-so-glorious debut in version 13.1, April 2019. According to the new features announcement:

"Premiere Pro now scales sequences proportionally by default. This supports workflows where the sequence is resized but the format is not changed. If you need absolute frame positioning, you can select that option in Sequence Settings. Absolute scaling is useful for projects where sequences need to be reframed while maintaining image positioning."

So, sequences should scale proportionally when the frame size changes, right? And if you uncheck this option, it should revert to absolute scaling. But here’s the kicker: Premiere sticks to absolute scaling no matter what you do.

But then, the truth hit me like a freight train: this checkbox is not a sequence setting at all. After I poked around the XML code in the project file, I saw zero difference between sequences with this setting on or off. And if you have two sequences, tick one on, one off, next time you check, they’re both off. It's been hiding in the Sequence Settings all this time, masquerading as something unique to the selected sequence, but the truth is, this checkbox is really a system setting.

Yet, even after unmasking its true nature, I'm still left in the dark.

So, here I am, scratching my head and wondering:
1. What does this setting actually do?
2. Is anyone out there using it?

I’m all ears for any leads you can throw my way.

Stay sharp,
Paul

[R Neil Haugen]

Paul, that is extraordinary effort in sleuthing there. Never figured that out myself and will be curious about any additional information that comes up.

[Joost van der Hoeven]

@PaulMurphy , Sorry I do not have any answer or insite to your question. Just wanted to compliment you on the design of the image you use. It totally sets the mistery theme. Great job!

[Ann Bens]

When it was just released, I dived in but could not figure out what was happening or not. So left it as it was.

But then again, I hardly ever change sequence settings.

[karlsoule · Accepted solution]

I should probably wait to answer this until I've had my morning coffee, but here goes - be gentle if this is a little jumbled or too wordy. 

This gets into a lot of math and aspect ratio stuff, but the setting works when youre gowing from a lower resolution clip size and sequence size to a higher resolution clip size and sequence size. Its a conforming tool used when moving from a proxy to the original camera file, and youve done repositioning and scaling in the timeline.

Most films are shot at crazy high resolutions, like 6k, 8k, etc, and in the higher-end post-production facilities, the original camera files (OCFs) arent touched by the editor. A lab or a Digital Imaging Tech creates "offline" files or proxy files, at a lower raster size. So, the OCF may be huge in size, but the offline file might be half that - simple math, lets say the OCF is 6000 pixels by 3000 pixels, and the proxies are 3000x2000. The resolution of the editing sequence probably wont match the proxies exactly - often times, shots are framed for whats called a "center cut extraction", meaning that pixels along the edge of the frame arent typically used (except for stabilizing, or repositioning.) So, a starting editing sequence with 3000x2000 proxies might be 2500x1080, just showibg the center of the proxy frame, cutting off the edges. 

During editing, the director may want to move the clip up,down,left,right, to get the exact framing they want. Or they might choose to scale the clip up or down. The clips were typically shot with this in mind. 

At the end of editing, theres a point where an online editor wants to take the sequence and scale it proportionally up, and relink the clips to the OCFs, but wants to keep the same visible image. 

The default way that Motion works is based on a fixed number of pixels. If i cheat a proxy clip down 5 pixels, and then i start connecting the hires, and make the sequence bigger, the move down will be too small. The visible image in the frame wont match. 

This setting makes these moves and scales proportional, not a set number of pixels. So, when its time to conform the sequence at the end, all of this centering, repositioning, scaling, will still look the same with the original camera files attached. 

Does this make sense?

[Remote Index]

Karlsoule,

@karlsoule 

Thanks for the response here. You'll probably want to check the math on your proxies after coffee. Also you probably want to qualify that the proxy workflow you're descirbing is not Adobe's "built-in" proxy workflow, but the more traditonal (manual) model.

If I understand your explanation correctly, you seem to be saying that this function applies to changes in clip resolution but not to changes in sequence resolution.

I think if you intersect the original question with your answer, you'll still find a couple of things are unresolved.

The first is that "Scale Motion Effects Proportionally" does not respond to sequence settings changes even though it is described that way. I note here that changing sequence settings (specifically resolution) was revised in the recent past (2022?) so that you can change these settings even on a non-empty sequence. (You used to be able to change them only for empty sequences). Given this new (ish) functionality, a user would expect the "Scale Motion Effects Proportionally" checkbox to do just that. I suspect that this scaling function was never 'updated' in light of the new sequence settings functionality.

Failing that, a user would expect a good explanation that it applies to clip size changes not sequence size changes. Particularly when the official documentation says "Allows the user to scale the motion effect while changing sequences" .

I mean - why limit it to clip size changes? what's the design logic there? - but okay, if you're not having it apply to sequence size changes then at least explain that to users.

I'm going to emphasize here that Adobe has once again put users into the shadowy realm of noir thrillers here due to its extremely poor documentation. If a function is not documented properly, how is a user to know if the software is behaving properly? Should they report a bug? Is it behaving properly in a way that is not understood? What should a user do?

R.

[karlsoule]

This is how I'd test this to see if it does anything:

Create a single, standalone project. (don't use Productions - it works fine with Productions, but I don't want to list out the steps to generate new source clips here.) 
Load some original camera clips into Frame.io.
Download the proxies. (Frame makes proxy file proportional to your original camera resolution. No pillarboxing/letterboxing. This is important.) 
Create a custom sequence that is smaller in size than the proxy files. It doesn't have to be a lot smaller, just a little smaller, so when the clips are placed on the sequence, a little bit around at least 2 edges get cut off. 
Turn on the "scale effects proportionally" check box in Sequence Settings.
Do some repositioning of the clips using the Motion properties. Scale a clip down to fill the frame. move another clip up or down.
Duplicate your sequence.
Create a new Project, call it CONFORM.
Copy the duplicate into the CONFORM project. 
In the CONFORM project, duplicate the sequence again, but rename it "no scale proportional" or similar. You should have two sequences in the CONFORM project - the original, and a "No Scale" sequence.

On the No Scale sequence, go into sequence settings, and turn off the "Scale Motion Effects Proportionally check box." (leave it on in the original sequence.)
Make Media offline in the CONFORM project.
Relink the media to the original camera files. 
In both sequences, make the sequences proportionally higher resolution. 

What you should see is that the sequence with the box ticked will do a better job matching the positioning/scaling of the original edited sequence. 

[karlsoule]

It's been a few years since I had to use this in a project, so I'm hoping someone like @Ben Insler can chime in here. This was something I remember getting added during the movie "Only The Brave," when the director wanted to double-check some drone shots for focus - it gave the assistant editor an easy way to relink the OCFs and preserve the framing being done with the Motion effect. 

It's still used by folks like Scott Adderton in his role as conform/finishing - he does conform in Premiere Pro for movies like "American Sicario" and "Don't Suck." I apologize if my math is off - it is early on a Saturday as I type this. But that's what it's doing. Both the resolution  of the clips AND the resolution of the sequence need to change to see it do anything. 

[Remote Index]

Karlsoule,

... and after all that testing, how would a user know if this function is behaving as designed?

Further:

"Both the resolution of the clips AND the resolution of the sequence need to change to see it do anything. "

This is additional, new information, not covered in your first response post. It's also not mentioned anywhere in documentation.

Have you tested it?

R.

[PaulMurphy]

Karl,

Thanks for cracking the case wide open.

Just to clarify, here's a description of what this checkbox does:

Use this checkbox when you start editing with low-res media in a low-res sequence, but plan to replace it with hi-res media and increase the sequence size later. This ensures that all scaling and repositioning done with the low-res media will remain proportional and accurate when the hi-res media replaces it, maintaining the intended visual composition.

Here's an example of how it would be used:

1. You have some hi-res media shot at 3840 x 2160, and you plan to edit it in a sequence that is 1920 x 1080, where the hi-res media is scaled and repositioned using the Motion effect.
2. However, you start with low-res media that is half the resolution of the original (1920 x 1080), so you edit in a sequence that is half the resolution of your final sequence (960 x 540).
3. Once you receive the hi-res media, you replace the low-res media in your Project panel.
4. Now all your scaling and repositioning is out of whack.
5. But if you go to Sequence > Sequence Settings, change the Frame Size to 1920 x 1080, and check 'Scale motion effects proportionally when changing frame size,' everything will look as it did in your low-res sequence.

Finally understanding the purpose of this checkbox feels like finding that missing piece of a puzzle that brings the whole picture into focus.

However, I would say that the descriptions provided for this feature in both the User Guide and the release notes are really lacking. None of them mention anything about replacing low-res media with hi-res media.

Also, as I said in my previous message, this checkbox appears to be a system setting, not a sequence setting, and this means it can have some unexpected behavior for the user. For example, if you are copy/pasting from one sequence to another, and the sequences have different frame sizes, it will paste to a different position depending on whether this checkbox is ticked or not.

My theory is that this checkbox needs to be moved to System Settings and given a better name and description.

Looks like this case is closed, but my work is never done.

Paul

[R Neil Haugen]

Thanks for the further elucidation of this most ephemeral and nearly undecipherable issue!

[Remote Index]

Paul,

Thanks for your efforts here.

Sounds like there's two things going on here.

The first is that this should be investigated as a bug report.

The second is that this should be investigated for its poor (incomprehensible) documentation.

@Kevin-Monahan 

R.

[R Neil Haugen]

Only two commets ... 

@PaulMurphy thanks for such an awesome post, yes including the fascinating image! ... done in such a way to both illuminate and to encourage such as Karl to post.

@karlsoule Thanks for the information! And handling the questions that "Remote" and others may float here would be really, really sweet of you!