brainiac
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So what about my suggestion in the old thread that it is really to do with polarisation of light? Look at the edge of this fellow's lower right cheek, where there is a brighter patch behind him, surrounded by darker. See the dark fringe along the surface of his cheek where his cheek is actually reflecting and refracting darkness from the darker areas almost immediately behind.
In my experience these edge effects are not confined to Zeiss lenses, and I have often noticed them on my 200 f1.8 which is also a superbly 3D lens. Viewed along the plane, most surfaces reflect/refract, and the light is often polarized by the surface. I have looked for this effect in my own vision, and surprisingly, I found lots of it. You can see it if you focus on the edge of a pencil which transit's a high contrast edge in the background, like the edge of a window. Light and shadow seem to bleed along the edge of the pencil, creating contrast against the background. The effect is a class of information which intensifies edges and gives you information about the 3D field. You can see this by holding up a finger horizontally and looking past it to the vertical edge of the window. Focus your eyes on the window edge and your attention on the 'bokeh' of your finger's edge. For me, there are two main things to notice: first, the bokeh of my eyes has hard edges, like Zeiss bokeh. The darkening of the sky through the window due to my unfocussed finger can have a very abrupt and sharply delineated edge, not a soft continuous tonal blend, and if you look carefully you can even see a lighter band above the darker. Yes - your finger actually lighten's the sky. This is positive interference - light is after all a set of waves. The smooth soft bokeh of Leica lenses seems to me to be an engineered fiction. Secondly, the corner of the bright sky appears to bite a little serif into my finger. If you turn your finger so that it is only 20 degrees or so from the vertical so that the bright sky is just a dagger, you see that the bright serif spreads further along the finger's edge. This is the same effect as the darkening on the edge of this fellow's cheek. The way light behaves around edges which are flush with the axis of propagation is quite complex, and I question the veracity of a lens which is designed to hide these effects.
Now look at philber's scultpure shot.
How is it that the sculpture looks strongly 3D against a very sharply focussed background? I think a lens that handles edge superposition correctly provides 3D clues all over the surfaces and edges of subjects. I think these 3D-inclined lenses show natural edge contrast that other lenses mess up. It doesn't require bokeh to show up, it is subtly and subliminally discernible in all edges of things in a 3D field, even when both foreground and background are hyperfocussed. Get edge contrast slightly wrong, and exit 3D look with a whimper.
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) I agree they have a popping 3Dish look to them. I've just seen that same look on almost every other lens capable of F1.2 and many many F1.4 lenses. I totally got that off my OM Zuiko 85mm F2 
