Advice on IR photography for schools

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Broric

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Just looking for a bit of advice :-)

I'm involved in doing science outreach in schools and one of the activities we do is looking at light and photosynthesis. We use a webcam which has had the IR filter removed for the classroom activities but I thought it'd also be cool to take a few IR photos of places/things that the kids can relate to (i.e. how does their local park/shopping centre/etc look).

As there's pretty much no budget I was wondering what the cheapest/easiest way to do this would be? Can I just convert any old digital camera by removing the IR filter or isn't it that simple?

Cheers
 
Simply removing the filter will give you a full spectrum image....you then need to install a cut-off filter to restrict the light to the wavelengths you're looking to capture (590, 720 etc. for IR)

Bob
 
According to instructions I've read, a bit of "congo blue" film should do that but I'm not sure if it's really that simple.
 
A screw on IR filter will also do the job if you can cope with the extended exposure times....Hoya R72 is a popular choice.

Bob
 
A lot of pre 2004 digital cameras had poor IR filtering,some can even be used hand held with a r72 filter,one old one you may get from ebay which is supposed to work well is the Olympus C2020Z
 
Canon Bob said:
A screw on IR filter will also do the job if you can cope with the extended exposure times....Hoya R72 is a popular choice.

Bob
Click to expand...

Any idea how much longer the exposure needs to be? Are we talking seconds or minutes?
 
Broric said:
Any idea how much longer the exposure needs to be? Are we talking seconds or minutes?
Click to expand...
The R72 has a filter factor of 16 (around 4 stops) but your exposure time will also need to take into account the efficiency of the IR blocking filter installed in the camera and this varies quite a bit....ie, it's not possible to forecast accurately without knowing the details of the installed hot mirror.

Bob
 
I have a full spectrum Nikon J1, and it can still be used handheld with a Hoya R72 filter, though sometimes I have to increase the ISO a bit, just depends on lighting conditions. Where IR excels on bright sunny days, it really isn't a problem.
 
Mr Perceptive said:
I have a full spectrum Nikon J1, and it can still be used handheld with a Hoya R72 filter, though sometimes I have to increase the ISO a bit, just depends on lighting conditions. Where IR excels on bright sunny days, it really isn't a problem.
Click to expand...
Your full spectrum body will have far quicker exposure times than an unmodified body because it doesn't have the hot mirror. When the hot mirror is still present then exposure times will be far longer as most of the IR is being blocked.....ie, if the hot mirror blocks 90% of the IR then the exposure will need to be 10x longer to capture the same scene.

Bob
 
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