Archived posting to the Leica Users Group, 2001/06/26

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Subject: Re: [Leica] Re: M Purity/B&W
From: Christer Almqvist <>
Date: Tue, 26 Jun 2001 18:24:20 +0200
References: <> <> <f05010411b75de85a2f9d@[]> <>

Somebody previously said:
"I know that much of the Leica glass is wasted on a film like Tri-X"
which resulted in the following exchange

>  > What is your knowledge based on?
>The fact that Tri-X Pan 400 is a very grainy film of fairly low resolution.

Resolution is one thing. Sharpness is another.
The basic difference between the two  is illustrated on page 1 of the 
Developing Cookbook.
You do not need resolution for sharpness.
Also, a grainy picture does not  need to look unsharp.

Looking at pictues of real life, I think sharpness, and even more so 
apparent sharpness, is much more relevant than resolution for getting 
what I simply call A CLEAR PICTURE

But then I also  prefer prints showing apparent sharpness, a.k.a. 
edge effect, to grainless prints. That's why I shoot HP5, in the same 
grain class as Tri-X,  at 800 and develop in Rodinal, a developer not 
famous for giving fine grain, but with nice edge effects. Street 
scences at night can look dead sharp with this combo even though 
resolution is low and grain is large

If you like resolution, Leica glass may be of particular importance 
to you if you shoot Tri-X. I assume that you shoot at low light and 
use you lens stopped down just a stop or two. This is very Leica 
glass excells. The resolution on you final picture depends on the 
resolution of several links in the photographic chain. But it is not 
like a normal chain which is as weak as its weakest part. For yor 
picture the resolution depends on the accumulated loss of resolution 
from each step of the chain. (See the formula to calulate this 
below.) If Tri-X gives you low resolution, then it may be 
particularly interesting for you not to lose any more. To achieve 
this, use Leica glass.

Fuji give the following formula in their Fact Book, but Erwin Puts 
say that the forgot to include the square root sign on both sides of 
the equation. R stands for overall resolution and r(one, two etc) 
stands for individual reslution, e.g. camera lens resolution, film 
resolution, enlarger lens resolution etc.

1/r = 1/r(one) + 1/r(two) + 1/r(three)......
- -- 
Christer Almqvist
D-20255 Hamburg, Germany and/or
F-50590 Regnéville-sur-Mer, France

Replies: Reply from "Mxsmanic" <> (Re: [Leica] Re: M Purity/B&W)
In reply to: Message from "Steve LeHuray" <> ([Leica] Re: M Purity/B&W)
Message from "Mxsmanic" <> (Re: [Leica] Re: M Purity/B&W)
Message from Christer Almqvist <> (Re: [Leica] Re: M Purity/B&W)
Message from "Mxsmanic" <> (Re: [Leica] Re: M Purity/B&W)