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Author Topic: alpha channel  (Read 1389 times)

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« on: September 20, 2017, 05:17 »
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Hi!

In after effects I usually have a white background for the composition, (but not as a layer). Would it be better to render it with an alpha channel? Is this more useful to a buyer?

I'm not totally sure about alpha channel. I presume this means the buyer has a transparent background? If so do I mention it in the title?

Thanks is advance!
Suzie :)


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« Reply #1 on: September 20, 2017, 05:29 »
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I presume this means the buyer has a transparent background? If so do I mention it in the title?

Yes and yes. It's important info that will help the buyer choose the right file. As for the white background... that's just used when working to better see what's going on, and will only be present in the rendered file if you don't use transparency (render with an alpha channel). You can change that colour to anything that you want in the comp settings. But whatever you change it to, it won't be in the final output if you render without an alpha channel. If you render a video with no background (with transparency), the 'background' colour will be transparent. If you render a video with no background (without transparency) then the 'background' will be whatever colour it's set to in your comp settings.

What colour you choose to render the background, on clips without transparency, will be dictated by what it is you're rendering. A white background behind white text might not look very good. A pure green background behind non-green content might be handy if people want to key the image. It really does depend on what you're making... but the background content of a motion graphics clips is an important consideration, just as it would be when filming or photographing something. 

« Reply #2 on: September 20, 2017, 05:36 »
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Yes, it's very useful to have an alpha channel. However, if it's just a simple object in the middle, and a pure color in the background it's very easy for anyone to remove that background. But for more complex graphics with semi-transparent edges etc., a perfect alpha channel comes in handy.

« Reply #3 on: September 22, 2017, 06:31 »
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Hello!

I think I understand it a bit better thanks to your help.

If I want to render with an alpha channel then Quicktime with Photojpeg doesn't allow RGB+alpha.

So this would mean using a different format and codec? I'm not sure which one. Took me a while to understand and get the right ones to be accepted by the sites I upload to. (I think you suggested them SpaceStock)

Do you submit one video with alpha channel and one without? Or is that pointless.

Would it be an advantage sales wise to have an alpha channel? I have got fairly simple animations, but a few have drop shadows and perhaps in the future.

Thanks for letting me pick your brains!
suzie :)



« Reply #4 on: September 22, 2017, 06:48 »
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Hello!

I think I understand it a bit better thanks to your help.

If I want to render with an alpha channel then Quicktime with Photojpeg doesn't allow RGB+alpha.

So this would mean using a different format and codec?


Yes. Most people use PNG, but I like to provide higher quality 10-bit files which means Apple ProRes 4444 that also allows an alpha channel.

Do you submit one video with alpha channel and one without? Or is that pointless.

That is pointless if you have an alpha channel. Some people submit a file with their regular encoding (h264, PJPEG, ProRes or whatever) and put the alpha channel afterwards. So the clip is twice as long.

Would it be an advantage sales wise to have an alpha channel? I have got fairly simple animations, but a few have drop shadows and perhaps in the future.

If you're selling stuff that is meant, or likely, to be used as an element, and not just a background, then absolutely. An alpha channel can save lots of time and headaches.

« Reply #5 on: September 24, 2017, 09:35 »
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Thanks for that, all a lot clearer.

So Apple ProRes 444 is accepted by most agencies?

And people that aren't after a transparent (alpha channel) can still use the video in the same way I imagine. If I have a white background on the composition it will appear white on the rendered video.

Thanks again, I really appreciate you passing on your knowledge.

Suzie :D

« Reply #6 on: November 08, 2017, 03:26 »
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All you need to do is provide an "Black and White Alpha Map" of your clip. This will  double the length of your clip without increasing the size too much but it will give your customer an option to remove the background if he/she wants to. And you can render the clip in any format that you normally use without caring about alpha channel or transparency.

« Reply #7 on: November 14, 2017, 08:04 »
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Ahhh, sounds like a good alternative.

I'll look at doing that. As I'm learning might take a while to figure it out but could make them more sellable.

Thanks for your reply, much appreciated

Suz  :)

« Reply #8 on: November 14, 2017, 08:34 »
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Ahhh, sounds like a good alternative.

I'll look at doing that. As I'm learning might take a while to figure it out but could make them more sellable.

Thanks for your reply, much appreciated

Suz  :)

Just make sure you test the alpha channel carefully. I have found that a separate black and white alpha channel output sometimes doesn't produce the same results (i.e. worse) as a true alpha channel, especially with more advanced edges.

Do 10-bit if you can.


 

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