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Old May 25th, 2004, 05:31 AM   #1
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Night Vision Imaging Methodology.

This is a speculative enquiry to see if anyone here works with intensified passive night vision into PD150 or similar camcorders and to learn and develop innovative and effective methods of using these and other devices such as IR Extend security cameras in news and nature documentary work.

The industry standard seems to be the US manufactured Electrophysics Corporation Astroscope system. The night vision news footage from the more recent world trouble spots has been apparently originated on their systems.

For non-US people, the costs of the system are a bit severe and un-gifted amateurs are unlikely to have the means of buying the system. It is a specialist service with a limited likelyhood of consistently earning the operator a living.

I have modified a less expensive UK built Pyser device to the PD150.

Despite not purchasing an Electrophysics Corp product, their people have nevertheless been generous in response to technical enquiries I have made with regard NV and the AGUS35 project.

There are one or two things I have discovered with night vision, one such being including ability to "see" reasonably well lit moving objects through light vegetation by a combination of panning and post-production frame blending (layer stacking).

So, any other ideas and operating methods will be greatly appreciated.
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Old May 27th, 2004, 08:18 AM   #2
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Here's a bit more which comes to mind for the PD150P-PYSER PNP via SW5042 lens set combination. This info may not be valid for the Electrophysics Corp Astroscope products.

Camcorder settings for moderate to bright intensifier image, appear to be best at 50fps shutter, 0 to 3db video gain, aperture auto. Auto-focus appears to work quite well through the SW5042 but I prefer manual setting.

For dull intensifier image, up to 6db video gain can be used but beyond that the intensifier display scintillation "video noise" or video noise from the camcorder itself can become too predominant for acceptable TV documentary production standard.

Setting the camcorder exposure dark, then brightening and contrasting the image in post appears to confer a slight improvement in image sharpness and contrast on a test pattern as does a 4x layer stack (frame blend). Layer stacking helps with real-world images. Underexposure has not been tested in real world situations.

Try not to equally mix IR and visible light in artificial illumination. One light type or the other must predominate otherwise it is next to impossible to get sharp focus. It does confer a cool if weird pullfocus effect if one light type is switched to another on the fly.

And that is about as much as I have learned.
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Old May 28th, 2004, 01:57 AM   #3
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Shooting with an image intensifier is really shooting the back of the intensifier tube, usually a micro channel plate, and that rear part is just a small phosphor screen, like on a b&w TV tube. The camera just focuses on the little tubes rear part ( macro ) . There is no changing focus happening at that point. You do have to focus the front lens that is on the subject side of the tube. In case anybody is wondering, you can't get any color info shooting with these devices. The rear 'screen' on the device is monochrome phosphor, usually green.
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Old May 28th, 2004, 03:19 AM   #4
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It's like the colour choice offered by Henry Ford - any color you like as long as it is black - or in this case, green. According to reading on the web, green is the colour in which the human eye has the greatest ability to distinguish the most numerous and subtle levels of tone and contrast.
Apparently this information is also carried in the green channel of three chip camcorders.

The autofocus I referred to was camcorder into the intensifier display. I haven't worked out why but the camcorder autofocus actually works through the macro lens set I use to close-couple the intensifier. I thought camcorders used an acoustic method of measuring distance but it may be the camcorder determines sharpness by comparing pixels and settles for the greatest number of differences which would equate to sharpness of image.

I imagine I can get it slightly sharper with a lot of patient manual focussing but its convenient to know one can haul it out of the box, set the zoom to frame the display and go in seconds.
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