Archived posting to the Leica Users Group, 1998/02/09

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Subject: Re: [Leica] Re: Film vs Lens Resolutuon - facts wanted
From: Erwin Puts <imxputs@knoware.nl>
Date: Mon, 9 Feb 1998 21:29:04 +0100

> I have heard it said that with the exception of the special purpose films
> like Kodachrome 25 - no ASA 200 or more film can resolve  (lines/mm)
> as much as the average (not special purpose) lens can.
>
> Does anyone have any hard facts on this?  I am speaking of resolution
> not contrast or edge sharpness or aberation correction - just ordinary
> lines per millimeter. If no facts are available, then opinions will suffice.
>
> Marvin Moss

This is a very difficult question.
First some facts from the sheets.
			1:1000 contrast		1: 1,6 contrast
Fuji Superia 200    	125 l/mm		50 l/mm
Fuji Superia 100    	125			63
Fuji Superia Reala	125			63
Fuji Superia 800	100			50
Fuji Velvia		160			80
Fuji Astia		135			55
Kodak tech Pan		320			125
Agfa APX 25		200
Agfa APX 100		150
Kodak TMax 100		200			63
Kodak Ektar 25		200

These figures in itself are meaningless.
If we look at the Velvia these 160l/mm are recorded with a contrast factor
of 30%, which is very low. If we go for a 100% contrast (no image
degardation) the same film can handle only 40l/mm.

The recent add by Zeiss in PopPhoto claims a resolution of 300 l/mm for its
MacroPlanar 2,8/60. This claim I find on the high side. Leica lenses easily
handle 150 - 250 l/mm (areal resolution!!!!). But that is not the question.
Looked at the MTF curves the important figure is the contrast transfer at
80 l/mm. Most lenses have really trouble getting this relatively low value
on the film with a good contrast.
So here you have it; on the face value most modern films will 'handle'
around 125 - 150 l/mm. Most lenses can on one count easily top these
figures and chalk up values of 150 and 300 l/m, depending on the
measurement method. This comparison gives the plus to lenses.

But lenses also are really in trouble to get 80 l/mm. In this comaprison
the film easily wins. If you go for high contrast transfer for both system
components (film and lens); the film can handle 40 to 80 l/mm and the lens
can handle 20 to 40 lines (or to be a bit tolerant 80 l/mm). In this
comparison both components are about equal. The best lenses just outperform
most films and the best films just outperform most lenses.
Are we lucky that with Leica lenses we can have the best of both worlds.

Erwin