For those interested here is a link to Jack Pettigrew's comments as
published on BirdingAus in 1997:
http://bioacoustics.cse.unsw.edu.au/birding-aus/1997-04/msg00006.html
Note that Jack makes no reference to the use of camera flash and his
comments appear to be based on personal observations and not any
scientifically based tests.
I don't say that to in any way denigrate what Jack has written or to
denigrate his knowledge and expertise but simply to point out that his is
not a statement of fact. Just as my comments below are not statements of
fact either but rather an opinion.
It is interesting to me that no one has bothered to investigate this at a
clinical level considering the continuing interest in this topic and the
continuing dissemination of very subjective statements about how spotlights
and camera flash cause or do not cause damage to birds eyes.
Maybe a prospective PhD student who is struggling to find something worthy
to study which hasn't been done before could take up the challenge.
But that would mean at least another 3 years would pass before we would have
the (possibly) definitive answer to this perennial question.
Perhaps in the meantime one of the many actually appropriately qualified
academics who inhabit the periphery of this group** could point us mere
mortals in the direction of some resource which explains in understandable
detail the construction of the eyes of birds and how they work in comparison
to the eyes of mammals.
As an additional contribution to the subjective comments already made (over
a number of years) about this topic I can give my opinion based on my field
experiences with spotlights and camera flash.
Before reading my comments it would be worthwhile reading Lawrie Conole's
contribution here:
http://bioacoustics.cse.unsw.edu.au/birding-aus/2002-01/msg00504.html
Although I don't necessarily agree with Lawrie on every aspect of his
comments I do think his posting is one of the best I have seen on this
topic.
My comments: (note: the opinions expressed below are mine and mine alone. If
they concur with or differ from those of other group members then that is
purely coincidental.)
- Bird eyes are similar in construction to but not exactly the same as the
eyes of mammals. From that point of view it is fair to believe that light,
especially light intensity, may affect the eyes of birds and mammals
differently;
- As has been stated by Jack Pettigrew (and other authorities) birds (even
birds of the night) are able to look directly at the sun and put the image
of the sun onto their retina without immediately causing any obvious
detriment to the eye. But it would be foolish to imagine that if a bird was
to look directly at the sun continuously for an hour or two that no
long-term damage would be done;
- No handheld spotlight that I have seen has had a light beam the power of
which approached to any degree that of the sun. Perhaps there are military
class spotlights which are as powerful as the sun but I don't classify a
spotlight mounted on a wheeled/tracked battle-wagon or a naval vessel or a
Hercules aircraft as a handheld device;
- The power of the light-output of a camera flash is probably greater than
that of any handheld spotlight but the duration of the flash is extremely
short often in the realm of thousandths of a second (more on flash below);
- Birds are often also able to filter out different colours thus making
their vision more capable than that of mammals. Perhaps this may also help
birds to cope with the intensity of some light sources - that is a personal
thought and I have no evidence to back that up;
- The power of the light-output of a spotlight is more critical with mammals
than with birds therefore spotlighting mammals should probably be done with
greater care using the lowest powered light as is practical. The ideal would
be to have two spotlights, one for the birds and one for the mammals but
that would not generally be practical when spotlighting alone;
- There is a revolution in torches taking place right now in that
semi-conductor replacements for the conventional light bulb are appearing on
the market which are a reasonable replacement for 'conventional' spotlight
bulbs in many cases. These devices are described as Super-bright LEDs. That
is, they are Light Emitting Diodes (LED) which emit an extremely bright
light. This light is not yet as powerful as the more powerful 'conventional'
spotlights but some models of spotlights and torches fitted with these
super-bright LEDs are quite useful and effective. They also have the
advantages of lighter weight (they only need 'D' or 'AAA' size rechargeable
cells) and the batteries last a lot longer on a single charge than the
average wet-cell battery spotlight. I recently spotlighted with a 3 cell
Maglite fitted with a Maglite super-bright LED conversion unit and 3
rechargeable AAA cells (in AAA to D size adapters) on my trip to North
Queensland and I am totally sold on the concept. Now I plan to convert my
various handheld spotlights to super-bright LED technology using conversion
kits available over the WWW. These conversion units are simple devices that
look like the bulb they replace and the conversion process usually consists
of simply removing the existing bulb and inserting the new LED unit;
Many of the bird photos in my new photo gallery at
http://ptiloris.smugmug.com/Bird-Photography-Trips were taken using flash. I
have been using flash in bird photography for many years and have formed
some definite opinions about the effect on the bird subjects:
- I don't believe that photographic flash has any immediate detrimental
effect on birds. I am not sure about the long term effect of continuous use
of flash on the same bird but I would think that the bird would have to be
subjected to an inordinate number of flash cycles before any long term
damage was done. I would be delighted to be enlightened by any genuine
contrary conclusions obtained by genuine repeatable research;
- None of the birds I have photographed using flash has appeared to blink or
look away as a result of the flash going off and I have never managed to get
a photo of a bird blinking at the moment the flash went off. Birds that have
looked away while I was photographing them with flash did so slowly and in a
manner which could be interpreted as lacking concern if not mild annoyance.
Some subjects have 'bounced' a few centimetres from their perch in reaction
to the flash but they have always returned immediately to the perch without
loss of balance or any appearance of disorientation. My interpretation of
this reaction has been that something happened which the bird did not
anticipate and thus the reaction was involuntary and a simple response to a
sudden change in the scene. In all cases the birds quickly settled down and
continued on with their activities, including foraging, without further
reaction to the subsequent flash cycles. That being said, I do not advocate
the use of 'flash extenders' in combination with the latest high-power flash
units simply because these latest flash units are quite powerful enough and
extenders tend to 'over-flash' the recorded image - in my opinion;
- The Sooty Owl in the above mentioned photo gallery actually flew into the
area lit-up by my spotlight (red cellophane filter equipped) and stared
unblinkingly at me while I took several flash assisted photos. After a few
minutes the bird flew off into the darkness confidently and without
appearing to bump into anything;
- One difficulty in photographing birds at night is being able to focus on
the subject in the low light so a fairly high-powered spotlight is a great
aid. I now use a spotlight with a red filter and the birds seem un-phased
while the camera seems to auto-focus even quicker than when using "white"
light.
This can be an emotion-inducing and divisive topic but I hope that everyone
reads what I have written above with an open mind. I genuinely believe that
birds are not adversely affected by the use of powerful spotlights but
mammals are a different proposition. In my experience it is obvious that
many mammals are uncomfortable in the beams of high-powered spotlights
especially if the light is unfiltered. Spotlights with red filters seem to
have only a minor effect on mammals, in my experience, and sometimes the
creatures seem to take advantage of that sort of light to assist them with
their foraging.
I don't believe that any of the birds I have photographed while using
spotlights and flash have been harmed by that activity. However, I would be
reluctant to participate in a group photography session where multiple
spotlights and flash units were to be used for a prolonged period of time,
that is, several minutes at a time.
Last of all, perhaps "Chris" could provide more details about the paper
he/she mentioned in his/her posting titled LED of Sun, 20 Sep 2009
13:38:01 -0700 (PDT).
** I can fully understand why some people are reluctant to enter into public
discussion of some of the topics presented on BirdingAus so I would be quite
prepared to act as a go-between for any "actually appropriately qualified
academic" who has worthwhile information on this topic. I will pass on the
info to the BirdingAus group while maintaining that person's anonymity if
they so desire.
Cheers
Bob Inglis
Sandstone Point
Qld
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