Camcorders and IR sensitivity

[Russell Rosener <rrosener@xxxxxxxxxx>]

This weekend I ran some tests using video camcorders and Hoya R72 IR filter
over the lens. The results were surprising:both cameras showed a
distinctive IR response! The camcorders are both older models made around
1988. The models and their results are listed below. I don't have specific
info on the type of CCD chip used, but it must have been common ten years
ago.

1. Minolta Master 8mm camcorder. Image sensor: 1/2 inch CCD. 4 Lux minimum
Illumination.
This camera with the Hoya R72 clearly showed the flourescent effect of
chloriphyl in green plants and trees. Clouds were rendered much more
visible and detailed. Skies were darker. This effect was clearly visible in
the B&W viewfinder. When played back on a standard color TV monitor plants
were monochrome, and all other areas had a reddish magenta cast. When the
color was dialed down, a conventional B&W IR image appeared. I believe
Hitachi made this model for Minolta

2. Magnavox S-VHS Movie Maker Model VR-9244AV01. Image sensor: Integral
color filter CCD. 1 lux minimum illumination with gain-up. (f1.2)
This camera had an even better response to IR, particularly when the "GAIN
UP" switch was used. In fact it created a grainy other worldly quality
almost identical to Kodak HIE film. Contrast was better than the Minolta,
and image quality had better resolving power. I have not run tests yet with
an S-VHS tape, but the quality should be even better. Matsushita made this
model for Magnavox.

Niether camera's auto focus worked effectively with the IR filter in place.
Manual focus outdoors was relatively simple. In conclusion, a Hoya R72
filter or equivalent can be used with most standard camcorders to produce
monochome IR images. This can be valuable as a preview for shooting Film IR
images, and to produce an IR video cheaply. It would be best to test
various camcorders to see the differences produced by newer sensors. In
general the more sensitive to low light a CCD is, the more sensitive it
should be to IR light.



**************************
*"Two And Two Make Five!"*
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* GEORGE ORWELL. "1984"  *
**************************
Russ Rosener
http://ascc.artsci.wustl.edu/~rrosener/


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