Thanks Rance01.

Yes, that's it... although, in fact I'd initially expected, because my magnifying glass, in my scene, is a reasonable distance from the camera... and what is behind the glass is a reasonable distance away, behind the lens... to get the effect detailed in that physics blog link I'd posted above...

Basically the scene behind is actually shrunk, effectively, and also flipped upside down.

Least it looks like that could well happen in the real world, in the scenario I'm depicting.

What I've done so far today is now based on the shader from BionicRooster's Sherlock Holmes set, in Free Stuff here... which I discovered had a working magnifying glass shader on it already! So I've applied that to the magnifying glass prop I'm using (wanted a less ornate style of handle basically).

I need to get some reflection on it now I guess... so I expect a fresnel_blend node controlling the mix of reflection and refraction is in order... in Poser Pro 2012.

Apparently the IOR of Crown Glass (which I think is used in most reasonable grade magnifying glasses) is 1.523.

But not sure how that translates into Poser... I think I read previously that some heuristics are required?