Archived posting to the Leica Users Group, 2000/07/22

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Subject: Re: [Leica] Diffraction limited; bo-ke
From: Dennis Painter <>
Date: Sat, 22 Jul 2000 17:09:07 -0700
References: <000101bff414$ad658ca0$983140c3@pbncomputer>

Erwin Puts wrote:
<snipping some stuff I don't believe to be needed for my question, but
apolgizing if it is> 

>It is
> always best to use the widest aperture that is feasible in a given
> situation. (when using modern leica lenses).

I am curious, why is this?  If I am using a modern leica lens that is
not diffraction limited then why not use it at f/16? 

<snip, again Erwin, tell me if I deleted the important stuff here> 

>Any out-of-focus plane has
> a higher aberration content than the plane of correct focus. 
>In fact, one
> could describe the effect of the sum of all optical aberrations on an image
> as a defocus effect. The out-of-focus plane then shows a higher level of
> aberrations than the true focus plane. 

So can the differences in aberrations between two lenses be compared by
comparing the OOF plane? Can we tell which lens has more aberration by
looking at the OOF plane? It sounds like it to me, and the OOF plane is
certainly visible in an actual photograph.  Gosh, what if I liked the
OOF plane rendered by the lens with more aberations? 

Really just wanting to know more about why not use the smallest aperture
of my leica lens if it's not diffraction limited.


In reply to: Message from "Erwin Puts" <> ([Leica] Diffraction limited; bo-ke)