[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: UV photography



Silvio Renesto inquired about ultraviolet photography.  I haven't done it
myself, but I offer the following tidbits from an article in _The 8th Here's
How: Techniques For Outstanding Pictures_, Kodak Photo Information Book AE-94,
copyright 1972.  (Yes, I hang on to things).

Use a BLB lamp (NOT a BL lamp).  The author, Dr. Albert L. Sieg, used two
15-watt fluorescent BLB lamps.  These 15-watt lamps were identified by the code
"F15T8-BLB."

Use aluminum foil to control the light (keeping the bulb glare off the camera
lens and out of your eyes).

You may instead use a flash tube from an electronic flash unit to light your
subject.  If you do, remove the transparent plastic cover (which is a filter)
from the unit if you can.  Place a KODAK WRATTEN Ultraviolet Filter, No. 18A,
over the flash unit.  The flash technique is particularly useful if you want to
use a high shutter speed (such as 1/1000 second) to capture sharp action shots
(though for fossils this is probably unimportant).

You also must use an ultraviolet filter on the camera lens.  Any No. 2 series
filter will do: 2A, 2B, 2C, 2D, or 2E.  2A is probably most readily available.

Daylight films -- Kodachrome II, Kodachrome-X, or Kodak High Speed Ektachrome
films (Sieg uses KODAK EKTACHROME-X film) -- give strong warm colors.

Artificial light films -- Kodachrome II Professional Film (Type A) and Kodak
High Speed Ektachrome Film (Tungsten) -- accent greens and blues best.

With two 15-watt fluorescent bulbs 12 to 18 inches from the subject, and a lens
opening at f/16 and Kodak Ektachrome-X Film, the best exposure would typically
be about 5 seconds long, but bracketing is recommended (shooting at f/11 and
f/22 as well, for instance).  Exposure specifications depend largely on the
unique characteristics of the fluorescent material.

You should be able to get a good approximate exposure with a built in meter in
an SLR camera by reading the exposure up very close on the fluorescing subject
prior to zooming out or pulling back the camera for a wider shot.  Even so,
especially when shooting in color, exposure bracketing is highly recommended,
especially since long time exposures (1 second or longer) may actually require
twice the time exposure as the meter indicates (reciprocity effect).

A long time exposure will permit you to use a relatively small shutter opening
(high f-stop), which makes for superior depth of field.  This way, the focus
will be less critical, and more of the subject will be in focus.

As you probably know, transparency film (slide film) is preferable for magazine
print applications.

For an example of successful ultraviolet photography, see the exceedingly
controversial article, "Pulmonary Function and Metabolic Physiology of Theropod
Dinosaurs" by Ruben et al. at:
<http://cas.bellarmine.edu/tietjen/Ecology/pulmonary_function_and_metabolic.htm>.
The "references and notes" at the end describe the light source used in making
the photos.  You could contact John A. Ruben if you need additional assistance.

Hope this helps!

-------Ralph W. Miller III
           ralph.miller@alumni.usc.edu