|
 A
superior mirage displaces images upward and includes at
least one portion that is inverted. On a superior day in
May in southwest Finland, a warm land breeze flows over
the cold sea surface while a freighter tends to business
as usual, and a viewer from the shore sees its hull
replicated upside down. Equipment: 400 mm lens with a
2.0 extender; cropped from the original. Pekka
Parviainen
The mirage is a true
thing:
a distorted image of real objects caused by light
refracting through the air. At times, when the vertical
temperature profile of the air near the surface (and
therefore its density) develops sharp differences over
short distances, light may bend significantly along its
pathway to our eyes, distorting what we see.
Compared to the expanse of the sky, mirages are tiny.
They are normally seen near the horizon, and show image
displacements of less than one-half a one degree (which
is about the same angular widths of both the Sun and
Moon in the sky.) For more information on locating
mirages, click on the Observing Primer link to the left.
Equipment.
SLR 35 mm camera, tripod, shutter cable release, 200 or
400 ISO film. For best results, a telephoto lens of
500mm or longer helps to isolate the mirage, and a
polarizing filter reduces haze and increases the
contrast. Digital cameras with digital zoom extend the
power of the telephoto position of the mechanical
optical zoom, but do so by interpolating the image with
an overall loss of quality, and may not result in the
quality you’re hoping for.
Composure.
Try to fill as much of the frame as possible with the
mirage itself. Avoid including extra scenery that merely
minimizes and distracts from the dramatic imagery.
Experiment with different camera heights, especially
with low angles just above the ground, as changes in
elevation as little as a few feet can make a great
difference in the curving pathways of the light to the
lens.
 Technique.
Keep exposures short, and according to your light meter,
since any camera motion—as well as shimmering from any
air turbulence—is magnified through the telephoto lens
along with the view. © Tim Herd
While mirages can appear
anywhere in the world, a motor convoy is engulfed by the
overwhelming sky in the Great Selma Sand Sheet, a flat
sandy plain of some 15,000 square miles spanning the
Egypt-Sudan border. Strong heating of the sand grills a
layer of hot air at the surface that cools rapidly with
height, creating inverted images of the land Cruisers
beneath them and bending skylight downward in an
inferior mirage in the desert in March 2003. Abed Wael |
