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Hi Doug,
its not quite that simple....
Firstly you need a camera that is senstative to IR...
Assuming you have a digital still camera, the actual sensors of the camera is very sensative to IR, but the camera manufacturer will have put an IR blocking filter in front of the sensor that blocks the IR and so the camera is normally only sensitive to visible light. Having said that, some IR does get through, but not much...
I had a Canon 30D. Using a visible light blocking filter which lets through IR - a Hoya R72 - I needed about a 10 second exposure at f4 in full sun with the camea at 800 ASA to get a decent image. After I had the camera's internal IR blocking filter removed, I could then do a similar shot in 'normal' time - eg at 100 ASA, at 1/1000 sec at f4. But to take 'normal' visible light photos, I had to have a IR blocking filter over the lens to re-compensate.
My 30D was stolen, so now my new unmodified 40D is back to long exposures for IR.
However there have been a few cameras made that had easily user-removable IR blocking filters. I think a few of the Sonys had these.
The other possibility is with a digital video cameras. Many of these are quite sensitive to IR, and simply illuminating the area with IR (eg from IR LEDs) in the dark will provide you with an IR image. If you want to do this in the 'light', then you'll need a R72 filter or similar over the lens.
I have a Sony video camera and it works very well with IR - it even has a 'night' mode in which a IR LED lights up and you get a good monochrome image in total darkness.
As for seeing your arteries and veins.... well, you skin is a bit more transparent at IR wavelengths, but you would still be lucky and need a lot of experimentation to be able to see much. Most of the photos of people that I have taken with IR don't show much in the way of arteries etc.
What you probably need is a specialist ... bloodsucker. Can't remember what they are called. I work in a hospital and if we have problems, we page a nurse that has special training and skills in jabbing folk with a syringe. He has his own office, wears what he wants and wanders around quoting Aunty Jack.
The other option is to use ultrasound or fluoroscopy and contrast to find the arteries.
I hope this helps!
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