[Leica] RE: I've seen the BOKEH!!!

[Simon Pulman-Jones <spulmanjones@lbs.ac.uk>]

I have been comparing pictures shot (wide open) with 35 Summicron (7 
element pre-asph.), 35 Summilux (1960 vintage), 35 Summilux Asph. (second 
version) and Noctilux.  All the pictures are from an ongoing project 
covering the work of a large psychotherapeutic mental health clinic in 
London and are of high contrast, low-light interiors.  More often than not 
the people who are the subjects of the pictures are dimly lit and 
surrounded by bright highlights in the background - typical Leica available 
light stuff. At first I thought I could detect the unpleasant 
'double-image' out of focus areas that some people have attributed to the 
35 Summilux Asph. - but then I started to notice that the other lenses 
sometimes showed this characteristic too. Having gone over and over the 
comparisons I am no longer sure that I can detect any difference between 
the out of focus renditions - each lens seems capable of producing smooth 
or double-image out of focus areas. The real difference seems to come from 
the fact that the double image type of out of focus effect seems to occur 
mostly on back-lit objects in more brightly-lit areas of the picture. The 
35 Summilux and the Noctilux seem to turn these highlight areas into smooth 
washes - the Leica glow - presumably because of the high aberration content 
of these lenses when wide open.  At the opposite extreme,  the 35 Summilux 
Asph. seems to present an odd, sometimes distracting and unpleasant, 
pattern of out of focus highlights - presumably because it is showing the 
highlight artefacts of the lens  in all their complexity rather than 
generalising them into a glow. My hunch is that the differences are not so 
much of 'bokeh' but of the handling of out of focus highlights. Another 
thing that is very noticeable is that the transition between in focus and 
out of focus areas is smoother with the old Summilux than with the Asph. - 
but only because the in-focus areas with the old Summilux are so nearly out 
of focus (soft) when compared with the Asph.  So the differences that I can 
see between these lenses are not so much to do with 'bokeh' (as I 
understand it) but with other aspects of the optical fingerprint.  My 
conclusion is that you are not automatically going to get the sought-after 
'pleasing bokeh' with any particular lens - all of the above lenses have 
sometimes given 'ideal' out of focus areas and sometimes not.  The 
difference in the way that lenses handle contrast and highlights in 
high-contrast, low-light situations is likely to have a far greater effect 
on the look of the picture than any differences in bokeh.  At least that's 
what now seems to me to be the most important factor...

Simon.