Sequence Editor Alpha layer import problem

I am having a problem with alpha layers in the sequence editor.

I am combining several layers with alpha together.

I have one image sequence that was rendered in blender blender .tga files
with alpha and set to alpha under.
This displays OK no problems

I have other elements that I made in Photoshop and wish to combine over and
under the sequence.
No matter what I do I cannot get the alpha layers to work in blender.
The Images are also .tga files with an alpha layer set to alpha under in the Seq editor.

I have tried all the possible permutations of settings when saving out from photoshop but to no avail.

It is rather perplexing since both files are .tga one works and the other doesn’t.
Does anyone know what I am doing wrong?

Many thanks.

Okay I found out what was wrong. I needed to check premultiply. and then scrub until it updates.
Why The images produced in blender should automatically display correctly and images made made by other means should be different I don’t know… But anyway I’ve got it working now. Perhaps premultiply should be on as default?