Archived posting to the Leica Users Group, 2000/08/08

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Subject: Re: [Leica] Performers and flare - DR. BLACKTAPE AWAKENS
From: "Henning J. Wulff" <henningw@archiphoto.com>
Date: Tue, 8 Aug 2000 16:20:17 -0700

At 6:01 PM -0400 8/8/00, Krechtz@aol.com wrote:
>In a message dated 8/8/00 4:50:33 PM Eastern Daylight Time,
>bdcolen@earthlink.net writes:
>
><< TIME TO CHANGE THE SUBJECT - PERHAPS TO FLARE SUPPRESSION?
>
>  >>
>Okay!  On a related matter, to what extent can use of contrastier or more
>saturated color print or transparency emulsions compensate effectively for
>lack of contrast in a lens, without introducing unwanted components or
>defects?  Similarly, in black & white, can conventional contrast enhancement
>techniques such as pushing be utilized, without unduly limiting scale or
>range?
>
>Joe Sobel

It can't. The problem is that flare suppresses detail. It's similar to a
lack of resolution. You can't ever get out more information than was there
in the first place. Once your detail is obscured by flare, it's gone. You
can use contrastier films, but they are the equivalent of sharpening
techniques, whether USM or other techniques. For some purposes the results
will be an improvement, but when you really get down to it, you haven't
restored the original contrast, you've just created a version of new
contrast that simulates the original contrast to an extent. Whether you
find this useful or not is a different issue. Often it is quite useful.

If you look at an MTF chart, you see that the graph is a report of the
contrast at various frequencies, with the comparison being of the original
(100%) against the result that the system being tested can reproduce. This
is never 100%, but gets close with the best lenses, emulsions etc. What you
are proposing is that we can shove the graph lines up closer to 100% by
choice of emulsion. Unfortunately, each portion of the photographic system
can only degrade what has gone before, ie, the lens cannot reproduce the
scene at 100% contrast at all frequencies, and the film cannot reproduce
what the lens sees absolutely perfectly (100% contrast transfer function
result at all frequencies).

We can get rid of some of the data, but we can't add data.

   *            Henning J. Wulff
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