Photo Stuff

Is a hard to describe pleasing ‘roundness’ and depth to the image created by a very smooth, creamy transition between in-focus and out of focus parts of the image. 

The Rolleiflex people used to refer to this quality as ‘plasticity’. Bokah refers to the quality of out of focus parts of the image, plasticity has to do with the transition between sharp and blurry. I used to think this was a result of uncorrected aberrations– the effect of which is that a sharp edge will be rounded off - just a bit. Maybe its that smoothing that creates plasticity, at a small cost in ultimate resolution.

But then, I found an old Modern Photography article on lens performance, “Think you get sharper pictures by stopping down?” Looks like 1971 lens designers carefully balanced corrections for the center, middle zone and edge of the lens to maximize resolution 2 stops down from wide open. Wide open, the light rays from the edge sometimes created an effect as if a slightly soft image was overlaid on the sharp one from the center and middle zone. This effect probably created plasticity. It explains why lenses like the 135 2.8 ‘Q’ have such a creamy, vintage look wide open.

With a modern, better corrected high speed lens the in focus subject appears to ‘pop’ in high contrast and brilliant color, from a diffuse, beautifully blurred background. The look of the 135 ‘Q’ is very different, but just as pleasing in its own way.

Of the classic Nikon lenses I have used, the 85 f1.8 H and 135 f2.8 Q come closest to exhibiting the plasticity of a classic era Leitz Summicron or Zeiss Tessar. That’s one reason I prefer the old ‘Q’ to the more modern small 135s.