The recent thread on glass amethyst going to blue under
fluorescents reminded me of a mystery I’ve never been able to
solve. I thought perhaps someone on the list might have an idea.
Several years ago, I was sent some pink CZ (you remember the
“pink ice” craze?) to photograph. I’d asked for photos, but got
the comment “they kept coming out blue.” Pooh, I thought. They
probably hired a photographer who didn’t know how to properly
light
Well, I sent them on to one of the gem photographers I worked
with regularly. A week later she calls me up and say, “It’s the
darndest thing: every photo we shot came out blue! Bright blue!
We tried again, with another light source, and it’s still blue!
It looks pink under the lights, but on film its blue.”
She called another well-known gem photographer, and he basically
said, “yup, pink CZ turns blue on film.” I gather that in the ads
you see for pink CZ, the photos been scanned and the color
digitally altered.
What I don’t understand is why it happens. Anybody have any
ideas?
Suzanne, I will do a little digging on this problem later this
afternoon. I will assume that the photographers used the correct
film (daylight/Tungsten) for the light source. I have a hunch
that the type of film used does not record certain wavelengths
produced by the CZ and the film only “saw” blue. Another
possibility might be that the camera lens might absorb certain
warm bands and again the film only records the blue waves that
pass through the lens. I will have to dig through my collection
for pink CZ and try this one out. I think the color center for
lavender and pink CZ is either cobalt or neodymium, which can
result in some complicated optical physics. Will Estavillo, www.natureshop-gallery.com
Hi, Suzanne! I cannot tell you the technical reason because I
do not know what pink ice (CZ) uses as a dopant (coloring agent)
to make it pink. Manganese might be it.
Trace elements in various stones, coupled with the lights you
use to photogtaph them, and the film you use --can cause unusual
variations. For example, chromium colored emeralds are
notoriously un-cooperative on film. But other chromium-colored
stones (rubies, for instance,) photograph better than they
actually look! They’re butter. Pure butter! The red range is
better captured on conventional film than greens are.
Alexandrites are the other challenge-stones. They photograph
delightfully in incandescent light, showing off their delicious
ruddy colors. Greens? Fuggedaboutit! (Daylight alexandrites – or
even alexandrites under fluorescence… cannot be effectively
photographed.) Yes, they are retouched.
One example of another natural BLUE stone that never cooperates
is cobalt spinel. Shot in incandescent it always appears purple.
Why? Only mother nature and a few scientists at Kodak who aren’t
telling – know.
Suzanne: There are two possible ways I can think of to explain
this. The first is the less likely one. It is that some light
sources are not continuous spectrum. In other word, they do not
put out all the wavelengths of light. They put out some
wavelengths of red light, some wavelenghts of blue light, etc.
This is true of florescent and flach lighting in particular,
although newer bulbs are less prone to this problem and closer
to “full spectrum” lighting.
If the pink of the CZ is not produced by a wavelength produced
by the light you use, you won’t be able to see it and will be
left with whatever other color is being shown by the light you
have. In other words, your light source doesn’t have the pink
wavelengths necessary to show the pink in the CZ, but it does
have wavelengths that show the blue that is there but usually
overpiwered by the pink.
The second possiblity is more likely. Color film has layers
sensitive to different colors. Just as the lights might not be
sensitive to all the reds (pink is a light red), the color layer
for red in the film might not be sensitive to the pink of the
CZ. However, some blue is produced by the CZ and the film is
sensitive to this. To produce the pink you would need a film
which has dyes which are sensitized differently.
I have oversimplified a little, as sometimes the color is
produced by combinations of different layers (remember yellow
paint and blue paint giving green in kindergarten, kinda like
magic??). However, the basic idea is the same. This problem
makes sense to me, as it often used to be said that violet
flowers turned blue under Ektachrome. Kodak worked on this
problem, and I guess it is much better now that ten years ago,
but I guess no one has solved the CZ problem yet.
That’s an intriguing observation that you and your photographer
friends made. I don’t know the answer for sure but it’s probably
related to the various dyes that manufacturers use to sensitize
the red, green and blue layers of emulsion in color film.
Actually, the blue layer doesn’t have to be sensitized because
silver halide particles are naturally sensitive to blue light.
However, the red and green layers MUST be activated by dyes that
are sensitive to certain wavelengths of red and green light. If
the particular Pink color of CZs doesn’t contain the right
wavelengths of red and green light, those layers will NOT be
activated and the slide or negative will not contain enough red
and green dye to offset the blue dye formed in the blue layer.
Therefore, the gem will look overly or completely blue. The eye
doesn’t depend on these same dye sensitizers to perceive colors,
so we may see things a bit differently than color film “sees” it.
Incidentally, neither does the color-sensitive receptor (CCD) in
a digital camera depend on these exotic dye sensitizers, to
produce color images. So, it would be very interesting to
photograph a pink CZ with color negative and color slide film as
well as with a digital camera and compare results. I’d guess that
the digital image would not have the “BLUES” like film does. If
you can do this I would LOVE to know the results. Fascinating
problem. Bob Williams
PS. Different film manufacturers use different proprietary
sensitizers to get the color palettes they desire. Even the same
manufacturer will use different sensitizers for different
families of film eg., Kodak almost surely uses different
sensitizers in Kodachrome and Ektachrome. That is why their
images look different. If you’re a natural born experimentalist,
you might try films from different manufacturers and compare results .BW
I have recently purchased the nikon 950 coolpix and it seems to
have no problem photographing any colored stones… perhaps
the color change that some people are having problems with may
be due to the development process… This does not seem to
happen with high end digital camera’s.So far, I have
Photographed Blue saphire, dark green emerald ,yellow Topaz,
Clear cz,Amethyst and Peridot and have not yet had a problem.
Hope this may be helpful.Check out our new whitemetal casting
page as well as our lost wax casting page on our “Workshop” at
our website. Daniel Grandi http://www.racecarjewelry.com
Suanne -As far as fluorescent lights are concerned, you have to
remember that while at least some fluorescents give off light
that is white to out eye, this white is not a continuous
spectrum! It is composed of discrete wavelengths that when
combined look white to us. But since it does not include all
wavelengths, and since the amethyst probably does, insofar as the
wavelengths that it passes, and since some of those wavelengths
are apparently missing in the fluorescent light, it therefore
results in a different appearance than continuous-spectrum white
light does.
Another factor to consider, also considering light sources that
may be a continuous spectrum, is the dyes used in various color
films. There is a blue penstemon that I have often photographed
in Zion N. P. (P. laevis), which usually photographs pink! This
is a result of the fact that the sensitization of the film is not
100% perfect. It would be great if it could have perfect
square-wave responses in all 3 colors, but unfortunately
sensitizing with such perfect responses just don’t exist, as far
as we know (and believe me, Kodak – and Fuji too, i’m sure) has
looked at a lot of dyes!!!). So sometimes colors of certain
wavelengths just do not reproduce perfectly.
I realize this is pretty technical, but there is just no other
way I know of explaining it short of a treatise too long to go
here!
Thank you to all who suggested solutions to the “Blue CZ”
mystery! I suspect you must be correct, and it must be a quirk of
the film’s dye process. The photographers I worked with were
experienced gem photographers, and were aware of the lighting
issues several of you mentioned, including the question of
fluorescent lighting.
If the opportunity presents itself, I shall have to experiment a
little with different films. But if the situtuation ever arises
again, I think I shall simply suggest using a digital camera!