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Assembly and Operating Instructions for Kits


Photography of Birds in Flight using a Crossed-Beam Sensor



Click on any image for a larger version


  The photo of a tufted titmouse above was captured with a Crossed-Beam Sensor. The device has two intersecting beams. Both beams must be broken simultaneously in order to trip the camera. This means that the camera won't take a photo unless the region of intersection of the beams is blocked. This allows the camera to be prefocused on the area where the action will occur.  

  Set up and equipment  
The equipment--other than camera, flash, and supports--needed to take photos such as the one above includes a control box (left) and photogate frame (right). The two beams intersect at the center of the frame. The latter is connected to the input of the control box, and the camera is connected to the output. The sensitivity is adjusted according to the ambient light level.

A set up to photograph hummingbirds is shown to the left. The frame is mounted so that the center is along a typical flight path to and from the feeder. A camera with short shutter lag is used, as a hummingbird can travel far outside of the DOF region in the time it takes the shutter to open. The camera is set for full manual operation, aperture of f/22, shutter speed between 60 and 250, depending on ambient light. The two flash units, which are controlled wirelessly by the camera, are set at a low power of 1/32 to limit wing blur. Flash position and ISO are adjusted to get good exposure (ISO 800 in this case). The camera is prefocused a few inches in front of the center of the frame. This spot is chosen, because the hummingbirds tend to pull up in flight at about this spot before alighting on the feeder.


A photo of a rufous hummingbird taken shortly after passing through the intersection of the beams is shown to the right. Note that the bird is off center, because it flew a short distance with the camera shutter was opening.

  A typical shoot  

These are representative photos from a 1-hour shoot of broad-tailed hummingbirds. There are always many more throw-aways than keepers. The photos are uncropped unless indicated otherwise.

Left: Nice wing spread but the head is out of focus. Note that the tail is in focus; DOF is very shallow.


Right: The bird is moving away and was far from the plane of focus by the time the shutter opened and the flash units fired.

Left: Completely in the frame this time, but the head is out of focus and the tail in focus.


Right: Sharply focused head to tail and with a good wing spread. This one just barely made it in the frame. With cropping this is a keeper.

Left: Cropped version of the photo at middle right


Right: Keeper photo of the female (cropped)

  Keepers from other shoots  
Tufted Titmouse Carolina Chickadee Ruby-throated hummingbird (female)



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