Archived from groups: sci.electronics.design,rec.video,rec.video.production,rec.video.desktop (
More info?)
On Sun, 16 Jan 2005 02:11:00 GMT, Rich Grise <richgrise@example.net>
wrote:
>On Sat, 15 Jan 2005 19:08:21 -0600, Ron G wrote:
>
>> I didn't think it was at all possible to actually use a standard Sony, and
>> see through material.
>> That would be interesting just for checking if someone had a weapon or not,
>> under their clothing, whether metal, or a plastic knife, etc.
>> What modifications would be required?
>>
>I think there's some filter you take out.
Any Sony camera with Nightshot takes the normal IR filter out when
that mode is engaged. But you also need to add a visible light --
infrared photography (B&H and others carry these) - filter, in order
to see *only* the infrared.
Because some people used the things for voyeuristic photography, all
recent (about 6 years) camcorders disable the manual controls when
nightshot is enabled. It locks the iris open, max gain, which is what
you want for true nightvision. But it badly overexposes any daylight
shots (indoors may still be OK).
There may be a firmware hack to disable this, which would make the
thing more useful for daylight IR shooting. Otherwise, a ND filter
might be enough to make the exposure useful in bright light.
>Do a web search on "night shot", and when you pick your way through the
>nudie ads, there's sites that talk about using it as a spy-cam and such.
>
>And you don't really "see through" stuff - you just see the heat signature
>and no color. If a guy's got a gun in a shoulder holster under a tweed
>jacket, you probably won't see it.
Tinted glass is more transparent to IR, and also, IR generates less
reflections off the glass. Both combine to allow seeing through
windows more easily for surveillance.
It isn't actually Xray, and you won't see through clothes per se.
What you do see through is material which is less reflective to IR
than visible light. A lot of fabrics are tranluscent to IR (and UV).
Note that the effect applies just fine when used with IR lights at
nighttime. Sony Nightshot camcorders have an IR light on them, which
is what makes them workable for true "shoot in the dark" photography.
For low light photos, IR lights are one solution which is usually
cheap enough to try out, even if you don't have a camcorder/camera
with an IR mode like Sony's Nightshot.
There really isn't a true "light intensifier" circuit per se for a
CCD. Some cameras allow for increased gain-up, increasing noise
(picture graininess), but a post-process "brightness" software filter
(or the equivalent in a real time video processor hardware box) will
do almost the same thing. It doesn't actually increase detail in most
cases. It simply makes the entire picture brighter.
But that can be enough to make a low light picture more usable.
A better alternative, if you can't use lights (even IR lights) to
brighten the scene, is using a better low light CCD/camera. Size is
an issue -- the small pencil cameras have small CCDs, and that affects
the light sensitivity. Bigger CCDs beat smaller ones for low light.
I'd go with IR lights (even small ones are a big help) and a night
vision camera which sees well in IR.
--
*-__Jeffery Jones__________| *Starfire* |____________________-*
** Muskego WI Access Channel 14/25 <http://www.execpc.com/~jeffsj/mach7/>
*Starfire Design Studio* <http://www.starfiredesign.com/>