grover larkins
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 p.1 #1 · Flash Photography - Use in Wildlife and Bird Photography | |
This topic comes up amongst wildlife photographers in the field a couple of times a decade: "Is flash photography harmful to....?" I'll provide some answers to that on a scientific and a practical level in the following paragraphs.
Consider what an exposure under full sun at noon is - "Sunny 16" - or f16 @ a shutter time of 1/(film ISO). For ISO 400 film/sensor setting this then is f16 at 1/400 sec. This is a tolerated amount of light for species that are not strictly nocturnal/cave dwelling etc. (more on this later).
Next let's consider the output of a large, shoe mounted, flash unit with an advertised Guide Number of ~ 200 feet at ISO 100. The real, measured, GN is almost always between 50 to 70% of the advertised value when used outdoors (I've measured quite a few of them over the years). At ISO 400 the Guide Number is doubled so our flash unit has a real, outdoor, measured, Guide Number of about 200 feet. That flash unit, at full power output has a duration of ~ 1/400 sec.
Ok, now we have our numbers, here's what they actually mean in an example:
The animal/bird etc. would have to be at about 13 feet @ f16 for a full power, manual 1:1 flash (as described above) to equal the sunny 16 rule at ISO 400. If TTL is used and the aperture is set to anything wider than f16 the flash will be putting out less light than a full Sunny 16 exposure. If f8 was used at the same 13 feet in TTL mode the flash would be putting out the same light as on a Hazy-bright day - 2 f stops lower than Sunny 16. This is 1/4 of the illumination (power per unit area) of a Sunny 16 exposure. Clearly there is zero hazard to the animal's health if the flash unit is further away than the 13 feet needed for the Sunny 16 exposure OR if TTL is used with an aperture wider than f16 as less light is incident upon the animal.
The next question comes about with - "Doesn't it disturb the animal?" This is often put as a positive statement of fact despite the lack of evidence. Here are the facts: If an animal looks at the flash but doesn't move away then it isn't being "disturbed" any more than it was by the average bumbling photographer being there in the first place. As an example, in Costa Rica when photographing a Resplendent Quetzal I found that the male bird found my wiggling the fingers on my left hand whilst triggering the camera with my right to be absolutely fascinating even though I was 200 feet away.... I have photographed ducks using a flash for an hour without any issue at all but when another photographer whipped out a tripod they vanished in a cloud of water and in a panic. Clearly the presence of a three barreled gun (tripod) was "disturbing" but a hand held lens and flash on a extension bracket was just fine. Ducks are hunted and they know good and well that nothing good happens when a human shows up with a long stick like thing. Generally, unless you are using a flash unit on a nest or during a hunt, it isn't going to be a disturbance. Birds can, and do, vote to leave when they are bothered. It is up to US, the photographer, to think before approaching ANY animal - just being there can be unacceptable to some of them - if they fly off, walk away etc. DO NOT PURSUE THEM! They voted and want you "Off their island".
Nesting Birds and Flash: Here the rule is pretty simple - avoid bringing any attention to the nest if at all possible. The chick cannot go anywhere and, if "outed" becomes a tasty snack for a predator. You may cause the parent to either attack you or expend energy (and time away from the nest) trying to entice you away from the nest. Both are bad for the chick and really, really, wrong. Flash can be used, for example on an Eagle nest or openly visible Hawk or Owl nest. It isn't "hidden" and generally will have little effect on the chick UNLESS you discover the following situation is YOU.
The Flash Pitfall: You have a nice flash unit but it just isn't going to work to get a photo of the subject at a respectful, non-disturbing distance because your lens has a maximum aperture of f8 and you would need to be within 26 feet to get a properly exposed photo using the flash I described earlier (top of the line Nikon/Canon). Unfortunately you notice that the birds become agitated when you get within 50 feet of the nest (or you don't because you are oblivious) but you "Have got to get that photo, it is only one..." Here is where YOU (not the flash unit) become THE problem; you have allowed your desire to jeopardize the survival of the chick. The more anemic the flash unit, the closer folks try to push in to the nest... this never ends well.....
Finally, nocturnal and/or cave dwelling species: flash is largely a bad idea on these - bats flying through the night sky is fine, flash away, they are not using their eyes.... Bats roosting in a cave is an invitation to be the guest of honor at a guano shower - a real sh*t show from what I've heard from an idiot who inadvertently did it trying to photograph a cave cricket.... Using a flash to photograph a pit viper can likewise be somewhat dicey - they can strike at the residual heat from the tube discharge... used to fill two balloons with water, one cold and the other warm and dangle them in front of a rattlesnake (Eastern Diamondback) - it would ignore the cold one but, as soon as the warm one came into view, it hit it HARD!
Moral of the story, flash isn't bad or good. Those valuations are reserved for the users - follow the guidelines above and you will have minimal impact.
All the Best,
Grover Larkins
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