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Old September 25th 08, 05:47 PM posted to rec.photo.digital,rec.photo.digital.point+shoot
Whiskers
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Default Infrared photography

On 2008-09-25, DaveC wrote:
I want to photograph and video in infrared mode.

I understand that some point-and-shoot cameras provide this style of
photography/videography. Alternately, some people have "hacked" a camera by
removing the IR filter from in front of the imaging element. There are
instructions on-line to DIY this, or to send in your P&S to have it done.

Basically, the IR filter is removed and replaced with another (not a
procedure for the faint at heart). The replacement filter is $$$.

My question is this: is this replacement filter that passes rather than
blocks IR available as a gelatin or other commonly available filter that I
can source elsewhere other than from these camera-mod services?

Or can I just strip off the existing filter and not replace it with anything?
I'm looking for quantitative data (the existence of IR) not qualitative data
(a pretty picture). What function does the replacement filter provide (other
than passing IR data)?

To clarify, I want to "see" IR images real-time in the viewfinder, not
post-process the image data to reveal the IR.

If there's another forum you suggest I should ask this question in, please
let me know.

Thanks,


Most digital cameras have some infra-red sensitivity left in - the
internal infra-red filters are there to stop most infra-red from getting
to the sensors, as it blurs the image (apart from anything else). The
infra-red filters sold to go in front of the camera lens do the opposite -
the stop most or all of the visible light but not the infra-red, so that
you can take pictures using only the IR. but because the intermal filter
blocks most of the IR, you need a long exposure (or an uncomfortable
amount of IR) to get any image at all.

It is possible to remove the internal IR-blocking filter from some digital
cameras (but probaly not compacts - the lens/sensor assembly in those is
ususally a non-servicable sealed module); usually you would then need to
replace it with an element having the same optical qualities in the
visible spectrum as the original IR-blocking filter had, or the resulting
images won't be usable. With such a camera, to get images using only the
IR spectrum, you'll need a filter in front of the lens to block the
visible light. All IR images from such a camera are likely to be more or
less blurred.

There are of course purpose-built thermal-imaging cameras, and IR 'remote
thermometers'. Some 'night vision' devices operate using 'passive IR'.
Oddly, these seem to tend towards the 'stupidly expensive' end of the
price spectrum, being targeted at the armed forces and emergency services,
or for industrial or medical uses.

This site might be useful
http://www.wrotniak.net/photo/infrared/#CAMERA.

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