[Leica] 35mm normal vs. ASPH or Spherical...Some nonsense

[buzz.hausner at verizon.net (Buzz Hausner)]

Thank you Henning, you have clarified something about which I have long
wondered but been too lazy to investigate.

        Buzz

-----Original Message-----
From: lug-bounces+buzz.hausner=verizon.net@leica-users.org
[mailto:lug-bounces+buzz.hausner=verizon.net@leica-users.org] On Behalf
Of Henning Wulff
Sent: Friday, November 19, 2004 4:35 PM
To: Leica Users Group
Subject: Re: [Leica] 35mm normal vs. ASPH or Spherical...Some nonsense


The main ingredient that results in 'good' bokeh is controlled, 
undercorrected spherical aberration. The number and shape of 
diaphragm blades controls the shape of out of focus specular 
highlights, and rays (diffraction rays) coming off in focus or out of 
focus specular highlights, and, in case of seriously adverse 
lighting, the shape of flare spots reflecting the shape of the 
diaphragm.

Double line bokeh, 'nisen', is the result of overcorrected spherical 
aberration, and is something I've seen in many Nikon lenses. Then 
there is the 'doughnut bokeh', which is a whole 'nuther flavour......

The ASPH Leica lenses have gotten spherical aberration under control 
so well that the bokeh benefits of it are largely gone. And of 
course, the resolution and contrast go up.

Note that the amount and type of spherical aberration can and does 
change to a certain degree with focussing distance as well as 
aperture. That's why a lens can exhibit somewhat different OOF 
rendition under different conditions.

My 4th gen Summicron 35, with 10 not-making-a-very-round-hole blades, 
has exceptional bokeh, only matched IMO by the 75/1.4. Both are 
superb. The 35/1.4 ASPH and 90AA are definitely 'sharper' wide open, 
but are also not as smooth.

So I generally use the 35/1.4 ASPH and 75/1.4, because the lenses are 
all good, and these are 1.4.

-- 
    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com
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