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Alphas and strobes
Hi
Hope someone can help…. I have been given some footage of pretty visuals on black backgrounds which are to be used as projections for a band.
They have alpha channels (and i am on unknown ground) The band want me to put stobes on to them at certain parts of the music (the track is provided its all computer stuff).
Except i cant do it. They just want the black to turn white without loosing the forground visuals…. Itried exporting the movies with RGB + Alpha which seems to make the black ‘solid’.. well at least keyoutable but that looks rubbish as theres many fine gradients in the visual. Blending layers dont seem to help, either loosing the whole thing to white (no forground color) or no strobe effect. I have tried with lights but that only lights on the foreground color not the black …
What do i need to knowAny help much appreciated
cheers
cris -
8 Replies
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Yes it is, Quicktime animation..Any ideas??
Cheers
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Ok Cris,
If that’s the case it should be quite simple. By strobe I’m guessing you mean a flash of white for 1 frame or similar?
If it truly has alpha, you should be able to check that by creating a new composition. Drag the QTMOV file into the comp. Now click the little checkerboard icon under your composition monitor. It’s just right of the 4 little colour channel buttons, the resolution selector etc.
Just like in Photoshop it turns on checkerboarding anywhere there is transparency (alpha). So you SHOULD see little checkers all over the footage IF there is correct alpha.
Assuming there is you can turn it off again.
Now a simple way of strobing only the background is by creating a new layer. Make it white. Now to make it pop on for only 1 frame at a time you can just a) either drag it so it’s only 1 frame in length and then position it, or b) keyframe the opacity from 0% to 100% and back to 0% again in the space of 3 frames which will make it flash on.
You repeat this for each strobe you want. That’s the simple way.
You could also create a layer and start playing with the STROBE LIGHT effect which can do the above with timing intervals and other little things.
And as I said, if alpha is actually present in the MOV, then the white strobe should just be BEHIND the stuff that is in the MOV assuming you put the strobe layer under the QT MOV layer.
Give that a go.
Alex
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Thanks for your detailed answers Alex, but i am afraid.. still no joy.
When i click the checker box everything disapears and i have just a checker box screen.
I have tried interpreting the footage as premultiplies which turns everyhting black and by ignoring alpha
which gives ablank screen.
Any ideas
the format information with the quick time says: Animation 720×480, millions+ integer(bigendian, stereo, 44100hz, 16 bitsAny lights you can shed on this most appreciated
cheers
chris -
Hmmmm,
without seeing it I’m starting to think that the alpha channel on that is borked. Could be that the person exporting it stuffed up somewhere. I imported a QT just like yours, Millions+ as well as audio…same deal…as soon as I click on the transparency icon I get the squares where the alpha let’s transparency shine though but not on the actual GFX that are not supposed to be transparent.
Scratching my head thinking if there is possibly a setting somewhere that is preventing you from seeing the alpha correctly or whether the MOV is truly stuffed.
Have you tried importing a QTANIM MOV that you created with an alpha? Seeing if that’s ok?
Alex
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Well i tried making and exporting a quick time animation from AE and the alpha works fine (when i export rgb+alpha)..Which makes us have to consider the footage..
Well its made in something called artmatic3 which thay have given me a copy of and i am exporting a test as we speak. The only setting for export are what sort of compression , size and length.. there is no reference to alhpas anywhere…
Any ideas ??
If i was to reexport a qt anmation from AE with rgb+aplhas would that help ??
cheers for the effert you have put in so far
it is really appreciated
thanks
cris -
Yeah that’s not sounding promising at all. I don’t think they are outputting proper alphas or even have the function to do that. Because there is no transparency information (alpha), even bringing it into ae and outputting it with alpha won’t create that for you. You would need to “key” it out like you often see with green/blue screens. But as you said earlier, that is bloody difficult to do properly when there is a lot of gradients and soft colours and all you have as the key colour is black 🙁
Going back to the original problem, you may have to compromise and simulate a strobe. You could always use the ADJUST effects like levels, hue/sat colourizing and others in that category to simulate the screen flaring out to white whilst still retaining some foreground information. As a strobe it would be really fast anyway so most people wouldn’t see the detail of the strobe.
I would try playing with that and maybe even stick a GLOW effect onto it. Or if you’re really game re-create the footage from scratch in AE with REAL alpha 😉
Alex
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Again,thanks for all your effrt with such detailed replys.. Recreating the footage in AE isnt really a goer , there is so much and its all generated mathematically from this artmatic thing, which while very pretty would seem somewhat limited……..
I like the idea of doing it with hues.. I has got me thinking about a filter i often see used in editing where the footage seems to burn to white .. Something like that or changing hue and saturation should do it i guess… I’ll give it a go and let you know how i get on.
Again big thanks and if youre ever in southern england theres a drink with your name on it….I checked out your site.. We had the same idea about the doing the family home movie thing how is it going is there much interest/any money in it ??
cheers
chris
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