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One of the most common aspects of a 3D effect is typically a narrow DOF to isolate the subject from background - the foreground separates itself from background. The Canon 85mm L F1.2 (Mark I & II) and the Canon 135mm L F2 both do this very well, but the images seldom look 3D. In a recent conversation with Son Min Pham I asked his opinion why the Contax 100mm F2 Planar achieves the 3D look so often. Son said the there are two key lens characteristics needed excellent micro contrast and excellent chromatic aberration (CA) control.

Micro contrast is the subtle tonality apparent in gradients. It is these nuances in the shading which create richness and depth in the color tones. These shadings give objects a roundness and sense of depth. What Son added (which I never thought about before) is that the micro contrast must be excellent across the entire frame. Some lenses like the Canon 135mm L F2 have excellent micro contrast in then center region, but not at the edges. On a tightly cropped portrait, the 135L will have a nice look, but on broader compositions, it will not maintain the “pop” across the frame.

The second characteristic is excellent CA control. Any fringing around the outline of subject diminishes the edge sharpness. The loss of sharpness around the edge reduces the perceived separation from the background, thus the 3D effect is lessened - or simply lost. The Canon 85mm L F1.2 is notorious for its CA at the wider apertures, the CA compromises the Canon 85mm L’s 3D abilities. Also, the Canon 85mm L F1.2 does not match the Contax 100mm Planar’s micro contrast levels.