@ bagginsbill,

Thanks for all your research, and for the very detailed explanation of this issue. Re your last post however; the previous two images I posted were rendered with the "Render Over: Black" option in the Render Settings, and still produced the fringe.

Just to be absolutely sure I tried this again. The background colour was bright green, "Render Over: Black" was used in the render settings. I moved the main infinite light to make sure the top of the arms was well lit, and did a FireFly render in P6, and exported as PNG.

I loaded the PNG in PSP 7 (trying a later version of PSP just in case). Then loaded clouds-002.jpg, Copied, and pasted as a new layer over the PNG. Loaded the alpha mask, inverted the mask. I am still getting a pronounced dark fringe. The image of the figure seems to be anti-aliased (or is it "pre-multiplied") with the black background.

What's got me stumped is that in the image by ghonma, it seems to be working for him, and it seems to be working for you, so why is it not working for me? The last image I posted is straihght out of Poser, and if you click to view at full size you can see that the fringe already exists at this point, so it is not a problem with PSP.

Thanks again for your help, but I guess I will just have to keep rendering over a background image.