T3D Pre-wheatstonian accidental stereopictures (was: from Euclid to Wheatstone)

[abram klooswyk <abram.klooswyk@xxxxxx>]

Peter Homer wrote (TECH-3D Digest 373, 2 Oct 1998):
>(...) it is just possible that Da Vinci produced some accidental stereo 
>pairs. This is because he drew a diagram of a kind of double camera 
>obscura with two pinholes in the same body (...)
>I dont know of any examples but if such pairs exist they could now be 
>viewed stereoscopicaly although almost certainly Da Vinci would never 
>have done so.

The French art historian and critic Pierre Descargues (member of the
Stereoclub Francais) has done some research on accidental stereo in old 
pictures, and he found quite a few examples. I don't think he had camera 
obscura pictures in his series. 
I have found a few examples myself, though mostly only a part of a 
picture shows the effect. Sometimes there are size differences which you 
could correct, if you wanted to do so.
The issue has some historical bearing, because Brewster said that the
Cimenti pictures were in stereo. This has been refuted.

A stereo effect in older pictures can also be seen when you fuse 
adjacent similar objects (crossed eyed).
Details of architecture, when carefully painted by an old master of
perspective, often show stereo effects locally.

Some years ago I have shown that in some of Fox Talbot's early 
photographs a local stereo effect can be seen by crossed-eyed fusion.
This might be the oldest existing photographs with an accidental
local stereo effect, although this can be discarded as a trick.
I have noticed the effect in pictures by Talbot of the cathedral
of York, Kings College in Cambridge, the Bridge of Sighs in Venice
and especially a photo of St. George's Chapel at Windsor Castle.
OK, this in the category of gimmicks.

Abram Klooswyk


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