Quote - It's not a bad method, it works quite well, but because the Poser image  of a figure was rendered over a background colour (mid grey for example) the edges are unlikely, in my opinion, to ever blend in quite as well as if it were rendered over a background image, where the anti-aliasing would merge the edges of a figure with the background.

Which is why you export to a format like .png that has a proper pre-multiplied alpha. The image you get this way is already antialiased correctly to merge with a background with no border or fringe.

Quote - In any case I don't see this as being in any way easier than adding a background image in Poser.

There are several drawbacks to doing backgrounds in render:

1. Everytime you change your mind about your background, you have to do a (potentially long) render. With a comp, you just switch out the layer to another image. You can also move/scale/rotate/color correct the background till you have exactly what you need.

2. You have no way of modifying the background blur without also screwing up foreground elements. With a comp since the background is wholly independent, you can just take a large soft blur brush and run it over various parts to make them match your render. But if you've already baked the background into your render you will have to do complex masking to get anywhere near the same level of control.

3. Poser AA does some very nasty things to textures. By pasting the background texture to a square which is then gonna be filtered to hell by poser, you're only reducing the quality of your work.

4. Cant be used in any sort of camera animation. If you really must use an 'in render' background, use a skydome instead. That looks better, can be used for reflections and follows camera motion properly.