Comments are often made as to
how such and such camera has a completely ineffective red-eye
reduction mode. Yet, the reality is that no on-camera system
is completely effective. Indeed, most are — at best — an
attempt at avoiding a phenomenon that only occurs if a flash
is used in a dim environment; quite often the problem is
almost unavoidable.
The
term "red-eye" is particularly appropriate for
people. The lighter the eye colour, the more pronounced the
effect can be. For people with darker coloured eyes, the
effect will depend on the quantity of pigment they have;
in some cases, the red-eye phenomenon will be significantly
attenuated.
The red-eye effect can be
quite different with animals. According to an article by
Veterinary ophthalmologist J. Phillip Pickett of the Virginia-Maryland
Regional College of Veterinary Medicine (writing in Scientific
American), domestic animals are even more prone to the
phenomenon. House pets have a reflective layer in the back
of their eyes — the tapetum — that enhances their
night vision. Apparently, the colour of the tapetal layer
varies to some extent with the animal's coat colour. For
example, a black dog will have a green tapetal layer, producing
a vivid green-eye effect.
While a buff-coloured dog's
tapetal layer will produce a pale blue-eye when it is struck
by the flash's light. Some
other animals, and a few dog and cat breeds, have no tapetal
pigment. These animals are therefore just as prone to red-eye
as humans. The rabbit on the right is an example of this.
Generally, with humans, the effect
turns up when the subject is photographed with flash in a
low-light environment, causing the pupils to dilate so as
to adjust to the ambient light. With animals, the effect
can occur even when the ambient light is sufficient to prevent
it in humans.
Red-eye reduction systems
Red-eye reduction systems come in different flavours, but all share the
same basic idea: force the pupils to contract, thereby lessening the possibility
of the flash's light reflecting off the back of the eye.
Two different systems are used to lessen red-eye. One turns on a bright
light pointed in the same direction as the lens. The other pre-fires the
flash, or uses short flash bursts, immediately prior to actually taking
the photo.
The success of either system is not completely dependent on the technology;
a number of other factors intervene which are beyond the capabilities of
the camera.
Luck is one factor. Should
your subject happen to look in the general direction of a
source of light just prior to looking at the camera, the
odds are the photo will show no red-eye effect, even without
red-eye reduction.
The same "green-eyed" dog shown above is captured at right in
a well-lit room, with one of the lights next to the photographer. The result
is that the dog's brown eyes are captured correctly.
Should your subject happen
to be glancing elsewhere while the red-eye reduction system
is active, it will most likely be useless. Put simply: no
red-eye reduction system is 100% effective. The image on
the left shows the problem. Red-eye reduction is used, but
the subject happens to be looking up at the ceiling during
the pre-flash, and at the time when the photo is captured.
The pupils haven't reacted to the red-eye reduction system,
and red-eye has resulted.
While no red-eye reduction system
is completely effective, some systems are more distracting
(or disturbing) than others. Systems that employ a series
of fast pre-flashes tend to be the most disruptive, while
systems that turn on a bright and steady bright light prior
to capture are the least troubling. Whatever the system,
they have one thing in common: they make the subject wait
for the photo, and can affect the spontaneity of the image.
A few tips
A few things should be considered when taking flash photos. Whether or
not a red-eye reduction system is used, the likelihood of the red-eye can
be reduced using the following tactics:
Position yourself so that there is a source of light near you. When
you take the photo, your subjects will be looking toward the camera,
with the nearby light making their pupils contract.
If possible, avoid taking flash photos in very dimly lit surroundings.
If this is impossible, then use the red-eye reduction system of the
camera and make sure everyone is looking at the camera.
Turn on a few more lights. The brighter the room, the more people's
pupils will contract.
Creating a proper lighting environment, or recognizing how to best use
the available light, is one of the most difficult things to learn in photography.
It is also one of the most rewarding, and can be the difference between
a plain photo and a good one. This is one case where practice helps, and
experimentation can easily lead to better photos.
When nothing worked.
The mere fact that the image is digital can help. Fixing a red-eye problem,
even using some simple software, is done by reducing the colour saturation of
the image at that precise spot.
1
If the software you use allows
it, select the precise area where the eye is red. Otherwise,
select a brush size (or tool size) slightly smaller than
the area to be desaturated. Be careful not to desaturate
the colours in the surrounding area.
2
Using the appropriate tool (or
menu option), desaturate the selected zone. If the program
offers a choice of colour to desaturate, then some experimentation
will be required. With a subject that normally has brown
or black eyes, desaturate all uniformly so that all 3 primary
colours are are brought to near zero and the red colour is
gone. With a subject with blue or green eyes, reduce the
red colour saturation to zero and adjust the other 2 until
the colour is correct, but subdued.
3
Last, using the selected area
or a tool with a size roughly the circumference of the pupil,
darken the eye slightly. If the change can be done selectively,
increase the contrast and lower the brightness just a touch.
With some software the process is referred to as burning
(the opposite of dodging), and a special tool is provided.
In all cases, the process must be done very gradually otherwise
the result will look unnatural.
Fixing a red-eye problem is within
the reach of many of the better image editing programs supplied
with cameras, such as Adobe Photoshop Elements, Adobe PhotoDeluxe,
and Arcsoft Photoimpression. Software that applies changes
in brightness, contrast and saturation to the entire image
cannot be used for this purpose.
The
term "red-eye" is particularly appropriate for
people. The lighter the eye colour, the more pronounced the
effect can be. For people with darker coloured eyes, the
effect will depend on the quantity of pigment they have;
in some cases, the red-eye phenomenon will be significantly
attenuated.
Some
other animals, and a few dog and cat breeds, have no tapetal
pigment. These animals are therefore just as prone to red-eye
as humans. The rabbit on the right is an example of this.
