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Photography using a cheap 830nm infra-red pass filter
Taken with the £29, 808#16D HD video camera with the rear hot mirror
replaced with a £9 (2015 price, excl. VAT), 6mm diameter, 830nm IR pass filter. The lens is screwed
out, the hot mirror prized from the back of the lens and a 6mm diameter
830nm IR pass filter (LPF-830-0601) pushed in to replace it. The lens is then screwed back to a point
where it focuses.
15 February 2013
As above, but with no sun and better focused.
Full size image (no
processing) 26 March 2013
....and on a
rubbish bag balloon (DxO distortion corrected)
How the HD 808#16D camera was converted for
use in the near infra-red
The HD 808#16D camera is supplied with the lens lightly
glued into the sensor housing. In the above image, the lens has been unscrewed and placed
hot mirror side upwards. The lens can be unscrewed without taking the back
off the camera. The replacement 6mm diameter, 830nm, near IR pass filter is in the bag on the left.
The rear of the lens with the square hot mirror in
place.
The rear of the lens after the hot mirror has been
gently teased out. A narrow scalpel blade is the best tool, or something similar.
Do not worry if the filter fragments.
The
830nm filter was pushed into position (update: 25 March 2013 - filter
now glued into place) ensuring that the lower surface was spotless! The
upper surface was cleaned before, very gently, screwing
it back into the sensor housing. This is best
done with the back of the camera removed.
To remove the back, two screws need to be removed from
the rear of the camera. It is worth investing in a spare lens unit,
should the lens or sensor be damaged, either during conversion or in use.
As a focusing aid, the edge of a sticky label, with
lines drawn 2mm apart, was stuck around the lens, but this is not
necessary if you are only using the camera for KAP.
The live video feed can also be used to focus the
camera, either via video out or using the USB lead and software like the
free Debut Video Capture.
The camera is a useful auxiliary for flying with a
higher resolution, visible spectrum camera.
The next step is to convert a camera for use in the
near UV. Three cameras can then be
flown together (52g) to cover the near UV to the near infra-red red. This
range can be extended into the thermal infra-red by attaching the cameras
to the housing of one of our thermal imagers.
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Near infra-red photography using old transparency film
as a filter on an unmodified camera
Photographic Techniques
| The standard
HD808 #16 (now replaced with the #16 V2-B) keyring camera with a disc of unexposed, but
developed, transparency film blu-tacked over the lens
aperture to act as a cheap
near
infra-red filter (2). A paper hole punch was used on a
tail-end piece of a transparency film.....look in old boxes of
transparencies. Two sample
images are below. |
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| Two near
infra-red images (video stills) showing a 'hot' spot. A bit
disappointing. |
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Very dull and overcast
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A quick look, holding a near infra-red R72
filter over the lens of an unconverted wide-angle HD 808#16D camera did not produce a
strong infra-red image or a 'hot' spot.
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There is no 'hot' spot with the unconverted
#16 V2-B, which is supplied with the hot mirror on the external surface of
the lens.
#16 V2-B keyring camera with a disc of
unexposed, but developed, transparency film blu-tacked over the lens
aperture.
Discussion thread
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