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Thread: Help! Difference matte

  1. #1

    Default Help! Difference matte

    I'm struggling with the Difference Matte in Premiere Pro 2 and After Effects 6.5, and I'd really appreciate some help:

    In Premiere I can create a Difference Matte that works perfectly... except it only takes up the central 2/3 of the screen. My video is 16:9, but whenever I export and re-import the matte image it comes back smaller.

    So I tried in After Effects instead... and found that the help files dont match the software, and there's no Difference Matte in the Keying options.

    Help!!!! I'm going bonkers!

  2. #2


    Would I be right in assuming it comes back 2/3 of the screen size horizontally only? If so you need to tell Premiere what pixel aspect ratio it is. I can't remember exactly , but I think the menu wording changed since Pro 2.

    Right click on the clip in your project window and look for "Interpret footage" in the menu that appears. It's now under the sub heading "modify", but for some reason I seem to remember it wasn't in Pro 2. Anyway, if this is the problem you'll find you can tell the software your clip is 16:9 in there.


  3. #3


    Thanks David.

    Yes it does come back 2/3 of the screen horizontally only. I'm sure you're on the right track, but I still cant quite make it work!

    In the Project Window my video is described as '720x576 (1.422)'

    In the Interpret Footage settings it says by default 'Use Pixel Aspect ratio from file: 'd1/DV PAL Widescreen 16:9'

    It has an additional option to make the video conform to a series of settings. I set it to 'Conform to: D1/DV PAL Widescreen 16:9 (1.422)' (Belt and braces!)

    I place the video in the timeline and check its properties. It still says 720 x 576 (1.422)

    I select File/Export/Frame. The settings are already 'D1/DV Widescreen 16:9 (1.422)'. I save as frame.bmp.

    If I import frame.bmp it appears in the Project Window as 720x576 (1.067) Alpha

    In Interpret Footage I can reset this to (1.422).

    Trouble is, when I use the Matte, there's no option to re-interpret the footage, it always imports straight onto the video at (1.067).

    Any thoughts?


  4. #4


    You could try changing the PAR when creating your matte rather than after bringin it back in. I can't remember how pro2 dealt with exporting still frames but it has definately changed now.

    On exporting is there anywhere you can change settings, if so. Change the pixel aspect ratio to square pixels 1.0 and the frame aspect ratio to 1024 x 576.

    If you can change these settings on export, I'm pretty certain that would work.


  5. #5


    Wow! Thanks for the quick response!

    I changed the export settings PAR to square pixels 1.0 and 1024x576, and this has resulted in the frame image being the right ratio in the Project Window when its imported. But the the Matte still only applies to the central 2/3.

    The Matte is working perfectly in the centre section, without any drop-outs at all, so it looks to me like the effect is using the frame image at the correct aspect ratio, but for some reason it's cropping it down.


  6. #6


    Cant find it now, but I saw a help file for the Difference Matte from a later version of Premiere. The later version had an additional option in the Effect Controls which was something like 'Use Matte full width' (cant remember the exact wording). That option isn't in my version of the software, but is this a clue?

  7. #7


    It's been a while since I used this effect, I thought it would probably have been aorund the pro 2 time, in cs5 there is the option "if layer sizes differ" and you can chose "center" or stretch to fit". But I'm sure that was there before, but maybe it was cs3 when I used it last, I would have thought before as I was well into after effets by the time I was using cs3.

    You have me curious, I'm going to experiment and get back to you.


  8. #8


    I'm not really sure what's happening here. It does work as it should in Cs5, and almost exactly as I remember from before. The only difference being that you can use a video as the matte, I seem to remember that it needed to be a still image before.

    You could try using a video as the difference matte, if it works and if you specifically need a still frame for the matte, you can find a hold frame command in the menu when you right click on the clip.

    If not, and if you want to try after effects.

    1. You need to put the matte (either video or a still) on layer 1.
    2. Put the video you want to cut on layer 2.
    3. and what ever video you want to show through on layer 3.

    4. Put the difference Matte effect on your video layer 2.
    5. Turn off layer 1.
    6. Adjust the effect values to suit.

    If you have PAR issues in AE 6.5 you will have a lot more control over them than in Premiere Pro 2


  9. #9


    I just had a thought, did you try rendering the section of the timeline with the effect on it?


  10. #10


    I just realised something, sadly it's not going to help you but it does explain something. The last time I was using the difference matte in Premiere it would have been in Pro 2 right enough, but I would have been using 4:3 video at the time. So who knows it might have been an issue.


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