CS5 - Interpret alpha as premultiplied

I have some QT files with premultiplied/matted with color alpha:
mjp2 - Motion JPEG 2000 32bit
1920 x 1080
30.000 fps
61397 kbps
AE imports these files with premultiplied alpha as default, but PR interprets alpha as straight.
Documentation says:
"Premiere Pro and After Effects recognize both straight and premultiplied channels,
but only the first alpha channel they encounter in a file containing multiple alpha channels."
http://help.adobe.com/en_US/premierepro/cs/using/WS1c9bc5c2e465a58a91cf0b1038518aef7-7c6fa .html
It does appear that these files contain both premultiplied and straight alpha channels.
If I import to AE then change the default alpha interpretation to "Straight - Unmatted",
I get the straight alpha key that PR is using by default.
Why would AE encounter premultiplied, and PR encounter straight?
Is there a way to force PR to interpret alpha as premultiplied without sending the comp to AE?
thanks

As you have determined, TGA is not one of the formats for which the importer provides this functionality.
AE imports .tif. and mjp2 files with premultiplied alpha as default, but PR interprets alpha as straight...
so you can add those two file formats to the unsupported list.
...so you must be using a third-party codec---and that codec isn't providing the functionality to Premiere Pro, either.
Did you have a chance to download and import the Motion JPEG 2000 32bit premultiplied alpha file I posted (be25.mov)?
I did not install any third party codec to import this media to PR or AE. I would be interested to know if you have to.
Is there a reason that you don't want to work with straight channels anyway?
For elements I create myself and want to be able to comp in the PR timeline, no.
It is simple for me to render using straight alpha instead of premultiplied... and I will remember to do that.
The mjp2 - Motion JPEG 2000 32bit QT files are precomposed elements with embedded premultiplied alpha
and I will use AE for any comps that use these elements.
Documentation says:
"Premiere Pro and After Effects recognize both straight and premultiplied channels,
but only the first alpha channel they encounter in a file containing multiple alpha channels."
Why would AE encounter premultiplied, and PR encounter straight?
Is there a different importer for each or is it a shared importer for both?
At this point, I will assume that PR does not support premultiplied alpha and plan accordingly.
I appreciate your time and effort tracking this issue.

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How come AE cannot interpret Alpha Channel from ProRes4444 ?

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I have tested his alpha channel works & it works in FInal Cut Pro X when I import it back to Final Cut Pro X to test it.
However, when I bring this file to After Effects CS5, it cannot recognize the alpha channel because the transparent part are all in solid black.
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Rick Gerard wrote:
ryan_khoo wrote:
Q1. But how do I check the file interpretation in AE ?
Q2. I am using AE CS5. Is it bcos you are using AE CS5.5 that you never have problem with ProRes4444 ?
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Q2. Nope... It's always worked. There were some gamma problems for a while, and a few other bugs here and there with ProRez, but if you're Mac is up to date you should have no problems with the alpha channel.
Thanks Rick for your help, I really appreciate it as I am not quite familiar with AE.
Q1. I did the steps you taught me & a new screen pop out. But under the "Main Options" tab, the section under Alpha, there are 4 choices (Ignore, Straight-Unmatted, Premutliplied-Matted with color, Invert Alpha). But all these was all greyed out. Any idea why ?
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Saving TGA with straight alpha (not premultiplied) and other weird stuff

Is there a way to save the alpha channel not premultiplied in a tga as I need straight alpha ... ?
While testing I got strange behaviour.... I have 5 bar from white to black with RGB value of 255,191,128,64,0
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cheers

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Hi,
Thanks for responding and getting back to me guys
@ Fuzzy...Trust me... I didn't think it would work...it didn't make sense to me either but I misunderstood Gerry...he doesn't know that I am operating exclusively on a PC using only PC based software...I don't have a MAC.
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Is there no way to interpret alphas as straight versus premultiplied in Premiere? Why do my transparent layers and clips with alpha channels display differently with a Black Video layer below them?
Background info:
I'm exporting my film to files with codecs that support alpha channels, not because I want an alpha in the result but because I need full RGB / 444 color coding for digital cinema theaters. I'm using ProRes444, Targa and PNG Image sequences to preserve as much quality as possible in my master exports.
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The result with the black video layer applied at the bottom is similar to the way QuickTime 7 displays straight alphas incorrectly. This problem occurs with both straight and premultiplied renders. The rendered text is from after effects and is stored using the animation codec.
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In my understanding, the reason 444 is indicated is because they are not RGB codecs. They simply sample the same amount of color as is possible in true RGB codecs. They still require a conversion from RGB to YUV for coding to a file, which almost always introduces a very slight shift in values, though usually imperceptible or acceptable. If the codec is truly RGB there is no need to indicate luminance vs color sampling.
...I think.
Again thank you for your awesome input! You've been a huge help here on my day off. :)

The lowdown on black vs straight alpha

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I use motion and livetype a lot, so I'm very familiar with the strange and interesting visual effects you get when you forget to switch alpha from straight to black (why does FCP not do this for .motn and livetype files anyway??)
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From page 372 of the FCP manual…
A_ Straight: Typically generated by a 3D animation or compositing program, straight
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Background Alpha export is arbitrary

It's been some time, so I'm starting over on the Apple boards. (Must have lost my profile)
I've read with interest the many posts regarding this topic before posting. Since I'm a Motion novice, this is the 1st place I look. Here's what's going on...
Using Motion to make those nice supers for my Avid (Mac 2.7) projects. Spent the last week exporting supers, all very nice. Yesterday, the lower thirds only exported with a black background. While I'm certain that there's a setting somewhere I fooled with, I can't get an alpha channel to save my sanity.
Previous to this seemingly arbitrary occurance there was no change in this hardware/software setup. It just stopped exporting w/alpha.
I checked the likely suspects...
Project background color slider set to 0%.
Channel in Canvas set to 'alpha'.
Each file exported using Animation (Millions of Colors +)
I avoid the "current project settings" export checkbox to avoid just such a case, instead I'd rather control the whole export process upon export. FWIW, there is no black background in the Motion project in question
For some reason, I'm unable to export a QT w/alpha channel. Perhaps when I try again, it will. This is a bizarre experience. I've been using alpha channels for decades, usually in 3-d apps and AE. A software codec selection should be honored by the app. Very curious.
Any thoughts?
G5 Dual 2gig - 8 g RAM Mac OS X (10.4.9)

Thank you for your thoughtful replies, but all the settings suggestions that have been mentioned are already appropriately selected, namely:
Canvas view channel to 'transparent'. (verifies that there is no background color in the composition)
Background Color selection in Project Properties reduced to 0%.
Exporting as Quicktime Movie. Export Options set under Video/Audio... Quality=100%. In Advanced Settings, Compression type is selected 'Animation'. Compressor Depth set to 'Millions of Colors+'. Quality 'Best'.
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The review pane on the right of this dialog verifies my Motion export settings as correct to obtain a Quicktime file with included alpha channel for compositing.
Upon import into Avid, file shows appropriate import processes for both graphic fill and alpha matte. However, imported Motion clip does not exhibit key properties. I employed a workaround, exporting Motion files as Animation Millions of Colors only, and using luma key to make the clip key. I've used several Avid codecs as tests from DV50 to 1:1 uncompressed, with no change in the outcome.
As the beginning of this thread indicates, I already successfully created a number of perfectly fine files using the above carefully-described methodology, which follows the documented procedures to obtain the desired result.
I appreciate the responses thus far. I wish I were just missing a silly button or selection somewhere. I understand that this is usually the case. For now, I hold to the thread title as an accurate description of this situation.
G5 Dual 2gig - 8 g RAM Mac OS X (10.4.9)

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I've posted screen grabs here: <http://www.flickr.com/photos/isabel95/7009088577/in/photostream> Click on "newer" to see the following two error messages.

you should not do that.
isabel95 wrote:
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TWAIN plug-in | Photoshop CS4, CS5
OpenEXR Alpha plug-in | Photoshop CS5 Extended
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Use the manufacturer's plug-in installer to install their plug-ins
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Hi,
There is a big bug in the CS6 , tiff file format have change, and when i generate a tiff file ( flaterned image with alpha layer) in photoshop CS6 or after effect CS6,
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If i open the image generate by CS6 ( photoshop or after) in photoshop (any version) or indesign CS6 alpha layer is working fine, but not in the previous version of indesign ....
If someone have an idea, a solution or a patch, it's can be a good help .....
Thanks
Mr

Yes, but photoshop CS5 and indesign CS5 work perfectly together ... Tiff create with PS CS5 was good for use in ID CS5 with alpha channel and was working fines... so it's was not really a big bug because it was working
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When I import the the images into photoshop even those areas which were transparent in Motion are black in Photoshop which makes it almost impossible to do any retouching (the subject in questions wears black).
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Thanx for your quick reply!
But actually it helped and created another problem:
I switched on the alpha layer in photoshop so I could see what was transparent in Motion, did some retouching and saved the image...
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CS5 - Interpret alpha as premultiplied

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