P3D Re I will Give 100$ to know

[Peter Homer <P.J.Homer@xxxxxxxxxxxxx>]

Charlie Hotchkiss wrote

>based on some Edwin Land articles.  I  produced very nice color pictures
>from black and white transparancies shot through red and green filters.
>Two pictures, two filters, project the transparancies through their
>respective filters and, hey presto, full color.  There was a ttrick to
>it, but there were only two b\w filtered slides

This is the basis of Lands retinex theory of colour vision there was a
Scientific American article about it. Two coleagues of mine attempted to
reproduce it I was away on secondment at the time but they found they could
not get it to work. Then another coleague pointed out they were trying to
do it from black and white negatives not slides !. Later they had some
slides done but I did not know this and when I returned from secondment
tried to do it with a student . First of all I copied all the slides
thinking they were negatives in order to reverse them ! of course that did
not work but neither did the slides .
 Land actualy goes on to describe  projecting the images through just one
of the   colour filters leaving the other white. I have come across an
explanation /criticism of land work that this little more than a
quantitative version of Goethes coloured shadows . Where you cast two
shadows one with a coloured filter and the other white light one shadow is
in the colour you use as might be expected but the other is the
complimentary IE Red will also give a cyan shadow.
There is an explanation for this but I am just of home so I wont go into it
now.
                                     P.J.Homer



------------------------------