David Dyer-Bennet & anyone interested in RGB photos:
I found a fascinating link on the Russian photographer Prokudin-Gorsky -
www.utoronto.ca/tolstoy/colorportrait.htm
It contains a photo he took of Leo Tolstoy as well as other RGB photos
and much info on how he accomplished such amazing photos so early.
Elsewhere I learned that Dr. Adolf Miethe worked with a cabinet maker,
Wilhelm Bermpohl, to build what Prokudin-Gorsky copied and called his
"large camera." Later he also used a smaller camera that had partially
silvered mirrors and RGB filters to take all three photos in one
exposure. I also learned that in 1901 Dr. Adolf Miethe used Ethyle Red
to sensitize orthochromatic film to red light thus making panchromatic
film and making separation RGB negatives possible, so Prokudin-Gorsky
probably used that technique and this is why his RGB separation negative
look so good. Dr. Adolf Miethe also invented flash powder. I am somewhat
amazed that it took Americans so long to develop our own version of
panchromatic film as the motion picture industry was powdering faces
white long after 1901. (Then again considering that over half of America
thinks Global Warming is not occurring or not man made and Erik Prince,
head of Blackwater, is leading together with his former boss, General
McCrystal, what he calls a "crusade" in Afghanistan and Pakistan ...)
Prokudin-Gorsky claims he could shoot the large camera that had the
"cassette" at the rear (which undoubtedly performed the RGB exposures)
in 3 seconds! When the weather did not cooperate his exposure lengthened
to 6 seconds. On ISO 320 with 29-61-47B tricolor set my exposures are
around 1/25 at f-16. Film must have been in the ISO 10 to 20 range in
the early 1900s so just the three RGB exposures must have consumed a
good bit of 3 seconds and that RGB back must have been a marvel of
innovation. I would love to know the details of that glass plate
"cassette." With a view camera it takes me about 2 minutes to shoot 3
RGB negs and even with the Hasselblad it takes almost a minute. What
amazingly clever fellows and skillful craftsmen those early
experimenters in photography were. As an engineer who worked several
decades in digital imaging it amazes me to imagine that in the very
early 1900s there were photographers creating color images of higher
color quality than any of the latest digital sensors available to us today.
Ed Scott
