[Rockhounds] colour perception, organic fluorescence, etc

[Horst Windisch]

Hi all,

Many years ago, some botanists ap[proached me to lend them a portable long
wave UV lamp. They were going to check for insects on orange trees, which
were affecting the orange trees. Cannot remember the results. Anybody heard
of this before?

Regards,

Horst

----- Original Message ----- 
From: "J. R. Hodel" <jr50wv at yahoo.com>
To: <rockhounds at lists.drizzle.com>
Sent: Saturday, December 13, 2008 4:11 AM
Subject: [Rockhounds] colour perception, organic fluorescence, etc


HI Axel, Kitty, et al:

Someone remarked about color perception, and this not only varies between
people but between eyes. Now I'll date myself . . . Back in the day when I
spent a lot of time in a darkroom and comparing color results from film
batch to batch, and from video camera to video camera despite the best job
the color engineers could do, I noticed that my eyes had slightly different
color responses. Partly this was noticable because back then you aimed a
film camera with one eye at the viewfinder.

One eye was closer to Ektachrome and one was closer to Kodachrome - go
figure. It's less noticable now, but still there. So comparing colors of
phosphorescence and fluorescence with the naked eye and discussing it via
email may be futile. Surely the color business has sensors that make this
all objective nowadays?

Axel, here in the North American forests we have several woods that
fluoresce under the right stimulation. Locust (I think the black locust
variety native to the WV forest) glows, as does the shrub sumac. This isn't
the poison sumac which I think is a western shrub, this is a shrub which
bears bright red fruit clusters with which you can make a pleasent
non-intoxicating beverage. It glows best in long-wave "black light". I don't
remember which spectrum locust responds to best.

Do we know what mechanism might cause the fluorescent reaction in organic
materials?

Just wondering, sorry if we're off topic, but it is related to black light,
etc.

Merry Christmas, everyone!

JR





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