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. 

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

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

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