An Explanation/Geekfest
Yesterday’s puzzler was how I made that freaky-looking picture of my dog. Dave of Pervasive Light came closest to the truth:
In fact, most digital cameras CCD’s have sensitivity to IR by default. (except for some of the canons, those b**tards filter out the IR) so you can drop a R72 filter in front of most digital cameras and get some amazing shots like this…
Jim Chen is an engineer and photographer in San Diego who discovered the exact same thing. That CCD “film” in your digital camera is quite sensitive to infrared light. In order to get natural colors, your camera manufactuer covers the CCD with a very thin IR filter. A clever and skilled person can (very carefully!) remove the manufacturer’s filter, and replace it with his own (precision cut!) R72 filter.
The result is a digital camera which takes infrared pictures with the same ease and speed as is once did in the visible spectrum. Without Jim’s conversion, taking an IR picture with a digital camera meant a tripod, a lot of patience, and a very long exposure.
I sent him my D70 a while back, after I upgraded to the D200. A couple weeks later, I became one of the only digital IR photographers in Colorado. And that wild puppy pic? All I used was regular old sunlight and a public chainlink fence for a backdrop.
I have to admit, I knew about this, but I didn
That’s fascinating.
Your dog is pretty darn cute too.
I actually use black and white film when shooting pics of my dog. He’s a Dalmation mix and he looks great in black and white.
If you want to test your digital camera’s sensitivity to IR, look at the LCD screen on the back while pointing a TV or DVD remote at the lens. When you press the remote buttons you’ll see little flashes of “blue” light that are invisible to the naked eye. That’s one of my favorite party tricks.
oh my god – did you hear that pajamas media blogger dan drezner killed himself this morning?
The filter over the CCD, isn
Ignoring the ravings of the insane …
Interesting bit of gear, Stephen. Long ago, I had fun with IR slide film, but its impossible to find and was difficult to process ( E-4 ) even when you could find it. I’ll have to show you my slides of the Santa Barbara mission in IR sometime.
KZ,
Yes that filter is called a low pass filter.
But it doesn
Jaymaster, thank you. But doesn’t the camera’s original Low Pass Filter (the one Stephen replaced) remove IR from the spectrum reaching the CCD? Or, does the newly installed filter block all but lower spectrum radiation?
BTW, the CCD (at least the way it
KZ, no, the original filter was a high pass filter.
As to why this all happens, silicon isn’t a direct bandgap semicondutor, so optical excitations are secondary scattering effects. There are other semiconductors that do much better and you really have to work hard to make silicon do optics even halfway decently. But with the electronics world paying the big bucks to get silicon working it’s still worth it to do the extra work to get silicon optics functioning.
There does seem to be some confusion here, and I appreciate the responses to my postings. I
Does this mean Steve’s camera is now one of the “see-through-synthetic-swimsuit” cameras, only higher quality than the ones from before?
Steven, your dawg looks awfully like my Maremma Sheepdog.
What breed is he?
Good question, Mr. den Beste. I vote Mr. Green travel to the nearest location with appropriate test subjects (female, 21-30, wearing the garments in question), perform plenty of experiments, and submit the results for peer review.
Stephen, thank you. My old digital camera is now in pieces as my husband has decided to go ahead and try to modify it into an IR camera! He’s just waiting to receive his new filter he ordered online. Here’s hoping he can put it back together!
Does this mean Steve’s camera is now one of the “see-through-synthetic-swimsuit” cameras, only higher quality than the ones from before?
[nod]