Nature Notes

August 29, 2008

Phototrap: Infrared Camera Trigger

Filed under: Birds,Photography Tips — Tags: , , — Harold Stiver @ 7:50 am

Mourning Dove

I have visualized the above image for quite a while, a Mourning Dove coming in to land with it’s long tail feathers spread, the white diamonds flashing. When I picked up a Phototrap Infrared Triggering system from Arizona Inventor Bill Forbes, my first project was to try to get┬áthis shot. The device works by sending out an infrared signal which is detected by a sensor. This triggers the camera, and it can be set to fire when the┬ásignal is joined or interrupted. Since I had plenty of Mourning Doves coming to my backyard feeders, I could work on it right away. Setting up the equipment turned out to be easy but working out the details of getting good images turned out to be a lot of trial and error but a very enjoyable experience.

Some of the problems that needed to be solved where as follows:

1. Where to set the sensor and in what triggering mode? I set up the sensor about 1.3 m. (45″) in front of the feeder and about 0.5 m. (18″) below it. It was set with the source and detector together facing up, and would trigger when the sensor received the signal reflected when the subject intervened. In this way, it was completely clear of the camera framing. The black rubber tub inverted under the sensor is to stop the squirrels from using it as a springboard into the feeder.

2. How to corral the subjects in to a more or less predictable flight path to the feeder? The feeder was closed off on three sides. I watched which way the birds approached the open side and placed the sensor on the most common path. This was certainly hit or miss, but even a low level of “hits” was fine for this project.

3. How far away to set the camera? This turned out to be one of the more important items. At first I set up much to close, but finally settled on about 6m. (20′). This allowed a greater depth of field compared to a close shot, and therefore gave me room for a greater shutter speed.

4. What camera settings to use? It became clear right away that a high shutter speed was critical,and was in the region of 1/2000-2500 sec. minimum. This was because there was no ability to pan a moving subject and also the subjects would make a very fast wing movement as they came in to land. You can see in the image below, that even at 1/2000 sec, there is some wing blur on the tips. I therefore set the camera in TV mode with a shutter speed of 1/2000 sec. ( or rarely faster if it was bright enough). Most lighting conditions available allowed for f/7.1 at ISO400.

Mourning Dove

5. What lens and flash settings to use? I ended up using a 200mm lens on my Canon 40d, which of course was pre-focused manually. The 550e flash was set at High-sync ETTL at -2/3 and a Better Beamer was used. This provided reasonable fill light.

6. Where to frame the shot in relation to the sensor and feeder, where to focus on, and how far to lead the subject? I wanted to obtain a full frame shot and expected that a great number of shots would be wasted by clipped parts. I set the framing so that it bottom was slightly below the floor of the feeder (Based on my observation of how this species flew in) and one side of the frame just about where the sensor would trigger. Of course there are many ways of working out a problem like this but this is what I came up with. After fine tuning, I can leave this set up for the morning of about 4 hours and expect to get 5-10 good images of various species. This is a very low percent of the number taken, perhaps 5%, but its all digital.

Mourning Dove


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