Motion 5's project-level alpha compositing wrong?

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Motion 5's project-level alpha compositing wrong?

Hi all,

I'm a very new Motion 5 user, and I am somewhat surprised by the color/alpha rendering and really aggressive antialiasing I am seeing in Motion. (I'm using the latest version: 5.0.6.)

Anyhow, to illustrate the issues I've been seeing, I made a simple test PDF in Illustrator and then exported it in a series of ways, which are illustrated below. (Though things look the same if I make the rectangles directly in Motion with the same colors...)

(1) PDF exported via Illustrator it to a PNG on a solid white background.

(2) I then imported this PDF into Motion and then exported a single frame as a PNG over a transparent background, which I then composited onto a solid white background in Photoshop.

(3) Then, I changed the background in the project properties to "Solid" and exported the a frame that way, thus letting Motion do the compositing onto the white background.

(4) Finally, I tried selecting the "Use Background Color" checkbox in the properties of the PDF media which causes the PDF to be composited onto a white background before any further processing happens in motion.

Note first that the text rendering is VERY VERY fuzzy from Motion vs. Illustrator (or Photoshop, where I added the white overlay text). Is there a way to tell Motion to antialias less aggressively?

Next, note that the alpha-compositing is VERY different when Motion composits the PDF against a white project background (case 3) versus all the other cases. The transparence is much more transparent looking!! This is versus how Photoshop or Illustrator composits 60% opacity against white (cases 1 and 2), or even how Motion does it on a media-specific case (rather than when compositing onto a solid project background), which is case 4. Has anyone else noticed this??

Finally, note how the color rendering intent changes depending on how the compositing was done, which is also pretty surprising.

Is there any way to control any of this? Is this some kind of bug? Or am I not understanding what to expect here? In particular, the fact that Motion seems to to do alpha-compositing wrong on the project background seems really problematic. Color rendering is an iffy thing to expect perfection from, and the soft antialiasing might be a design/aesthetic choice, but the compositing differences don't seem right.

Anyone have any thoughts?

Posted on Dec 21, 2012 4:23 PM

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Answer 1

fox_m

Level 6

12,208 points

Dec 21, 2012 10:52 PM in response to zpincus

Sorry if I come across like an idiot — I didn't actually read your message in its entirety — just recognize the complaint.

Exporting from Motion is *different* than creating an FCPX template. All templates are always treated as if they are rendered with "Best" settings. When you export: you need to manually set all that.

There are two ways.

1) Setting the Canvas Render settings (from the Render menu -- but depending on your project, Best can drag performance more often than not)

or

2) when you export, select the Render option in the export dialog.

These are the default settings...

If you left your canvas settings at Normal, then you can override those settings here. (Normal is always going to be a little "soft" when exporting.)

Personally, I think it's better to uncheck Premuliply alpha (I have NO idea why this is on by default!) What that does is take whatever your project background color setting is for the canvas (even though it's all alpha!) and blends it with the color/alpha of pixels being "blended"... it's designed to "aid" anti-aliasing as long as you know what kind of (similar) background you will be matching the graphic/video with elsewhere. The premultiply affected your export with a white project background creating that washed out look.

Set the Render quality to Best or Custom (there are extra text controls in the Custom dialog that pops up). I think the "fully optioned" custom setting is the same as Best anyway, so ...

[Fields is useless for anything other than interlaced video... do not know why they are checked by default (check the canvas setting for the defaults) -- but I don't think it makes any difference for stills -- same with Motion Blur and Frame Blending.]

These settings should sharpen up your exports considerably (and correct the coloring).

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Answer 2

zpincus Author

Level 1

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Dec 22, 2012 9:37 PM in response to fox_m

Thanks, fox_m, for your response.

Unfortunately, the problem I'm seeing is a bit opposite of the issue you described with the premultiplied alpha (etc). In my case, the of the output from Motion is correct when Motion exports with an alpha channel and I then composite onto a white background after the fact. However, the output from Motion is incorrect when the project background is set to "Solid", which causes Motion to composite onto the background itself and output a movie/image without an alpha channel. (Neither of these are affected by checking or unchecking premultiply alpha, I fear.)

Indeed, and regardless of the above settings, on the preview canvas the compositing always has a washed-out look where semi-transparent objects are more transparent then they should be. (Which matches the incorrect output from exporting with a "Solid" project background.) This seems to suggest that something is wrong entirely with Motion's alpha compositing.

As to the outrageously soft anti-aliasing, turning off motion blur and frame blending did nothing, I fear. It's frustrating, because when I go to the media pane and double-click on my PDF media, everything in the preview window looks sharp and correctly colored/alpha-composited. But on the preview canvas (and in the output), it's blurry, wrong-colored, and incorreclty composited. (See image...) I really hope I'm doing something wrong because this is very frustrating!

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Answer 3

zpincus Author

Level 1

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Dec 23, 2012 11:01 AM in response to zpincus

I made a simpler test case that I think demonstrates this to be a real bug in Motion. But I may be wrong... anyway, here's a demonstration project and examples of output versus what would be expected:

https://dl.dropbox.com/u/22248317/alpha.motn

https://dl.dropbox.com/u/22248317/AlphaProblem.pdf

Essentially, I would expect that a white rectangle (RGB 1.0, 1.0, 1.0) with 50% opacity composited against a black background would produce a 50%-grey rectangle (RGB 0.5, 0.5, 0.5). This is the result of, for example, Illustrator and Photoshop's compositing algorithms, or the built-in compositing in OS X. However, when Motion 5.0.6 composites such a rectangle, the result is RGB: 0.74, 0.74, 0.74.

This seems like a very serious departure from the usual Porter-Duff compositing rule!

If video (or a single frame) is exported using a transparent background, and then is composited onto a black background in Illustrator/Photoshop/Keynote, all is as expected and the color is rendered as 50% grey. However, on the Motion preview canvas against a black background, or if video/frames are exported with a solid project background, the color is rendered wrong.

Am I missing something here?

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Answer 4

fox_m

Level 6

12,208 points

Dec 23, 2012 2:56 PM in response to zpincus

You're absolutely right -- Motion is getting it wrong... with Motion objects. Motion seems to be importing and displaying Photoshop generated semi-transparent PNGs *more* properly (detectable alpha range in a test gradient was from 10.6% to about 85%). I tested a gradient in Motion, and it's pretty much opaque for about 20-24% of the object, then goes down to -- what you said -- about 74/75% opacity *through* the mid section, then tapers off rather quickly, so that about 15% of the object is totally transparent. The photoshop gradient is "evenly gradient" throughout the range...

I don't think Motion is as concerned about the "rules" as getting by "optically" or "visually" and quickly -- as quickly as possible (an optimization -- I'll bet if you ask a Motion engineer, they would say it was a "feature"). For most things "in motion" (moving), most people aren't really going to notice that critically.

If it is terribly important (and I'm not questioning that it is), you can adjust the opacity values in an object to more correctly reflect your intention.

Add a Filters > Color Correction > Levels to the object. In the inspector, turn down the disclosure triangle next to the RGB Histogram. Then turn down the Opacity disclosure triangle.

There are two properties you will want to adjust: White In and White Out. I find if you set the White In to about 0.8 (~ 80%) and the White Out to 0.74 - 0.78 (~ 75%), you can adjust the transparency (alpha channel) down to the values you want (if you are using a gradient or multiple semi-transparent objects within a group.) I thought about using just the Gamma (for solids -- this won't work for gradients) but I don't know how that would affect any exports for use in an application like Photoshop (simply did not test it.) Since I stated that the gradient created in Motion basically "falls off" at around 15%, you may wish to adjust the Black In and Out parameters as well. Truth is: you can fiddle with all the Opacity parameters to adjust the "spread" of opacity throughout the range (including Mix, which is global, if you need "smoothing"); for most objects, the White In and Out will be the shortest cut.

HTH

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Answer 5

zpincus Author

Level 1

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Dec 27, 2012 3:12 PM in response to fox_m

Thanks, Fox.

While I don't imagine that setting an object to 50% opacity (or importing media with such opacity) and getting 74% opacity could in any world count as a "feature" -- especially if the output produced differs depending on whether the project background is set to "transparent" and then the compositing is done after the fact, or the project background in "solid" and Motion does the compositing -- but I do appreaciate the help in knowing where to go to do color and opacity correction. I didn't realize the filters could do that, and I'm very obliged for your help with that.

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