How can I make transparency act as expected with the internal renderer? Seems like a z-buffer issue.

Everything seems fine in the material preview, but in the render the sky (or transparency, if no sky) "bleeds" a pixel or two between the intersecting part (intersecting in the 2d render, not 3d) transparent textured geometry and any geometry behind it. Hope this makes some sense:



Material/texture settings are as follows:




Changing transparency mode of the Texture from Straight to Premultiplied doesn't fix it.

blend can be found here: https://drive.google.com/open?id=0B8pm58kHwzU3M3hUZmdFdUhTdDg

The texture file separately can be found here: http://i.imgur.com/bRBRdX8.png
Tried a different texture file from cgtextures with no difference.
The main problem is anti-aliasing the alpha borders of the leaves. You should enable Full Sample in the Render options for best quality. This will render correctly:



Other problem for best quality might be the transparent texture itself. There is no color bleed over the transparent edge. There is black background over the transparent pixels.
On the leafs texture sampling and filtering happens. And the transparent border get's blurred and the black leaks into the leafs. The image without alpha channel should look like the right one:



Make sure when you are exporting the whole rgb channels are exported and not clipped with the alpha channel.