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Old April 12th, 2011, 07:53 PM   #16
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Join Date: Dec 2005
Posts: 877
Re: Going Batty...Need help with HD IR Video

The IR flash I referenced was just an easy to find example that looked like it might work for stills since its design purpose appeared to be traffic management. Some thoughts on how I might approach this not knowing much about the scale and logistics - First, I would assume I could take shots orthogonal to the direction of flight, e.g from the side or top. I would use a known speed for bats flying to determine the time it would take a bat to traverse the field of view of the lens being used. That would give me the shortest recycle time I might want. If I'm gathering statistics perhaps I don't need to get the maximum number of bat images, so really short recycle times might not be an issue. If it is, then I'd try to find a strobe with the needed sustained recycle time/flash rate. I would check to see if there are any gases other than xenon that might produce more IR, just in case I might get more benefit from a custom flash tube. If so, find a source for that (maybe the college physics department). Short recycle rates durations are generally inversely proportional to power, so focussing the beam with a fresnel like a Better Beamer or a page magnifier might help with keeping the required power per cycle lower. I'd find a cutoff filter at the highest frequency possible without disturbing the bats, placed over the flash tubes. Then depending on objectives, look at either triggering at single or burst frame rates using your sensors. One problem I forsee is the range of distances of bats to strobes so the exposure would tend to vary quite a bit, e.g. a bat at 8 feet would receive approximately twice the exposure of a bat at 11 feet.
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Old April 13th, 2011, 06:13 PM   #17
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Join Date: Nov 2008
Location: Melbourne Australia
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Re: Going Batty...Need help with HD IR Video

Hi Shea,

I have been using infrared to record the activities of some our smaller nocturnal animals (gliders, phascogales). As I could not find a camcorder that gave me control of shutter speed, aperture and gain I used cheap surveillance cameras and multiple lights. If carefully placed the multiple lights give some form and texture to the subject and a much more satisfactory image.

I have more recently acquired a JAI CV-M300 that has a 2/3” chip and shutter speeds to 1/10,000 sec. The CV300 permits full manual control. I have not done much with this camera yet because I work at close distances and as it is such a large chip I have to use longer focal length lenses to cover the same angle of view as my cheap ¼” chips. This means a serious loss of depth of field. I need more IR to enable me to use smaller apertures and so regain the depth of field that I was used to. More intense lights are coming.

The cameras I am referring to only have composite out and to record the images one needs a separate recorder. In my case I fed the signal from the IR camera to the line in on a PD150 which also served as a viewfinder. This gave me about an hour’s recording.

Good luck.
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