Recently I subitted a query to the photo.net discussion group (will add URLS here) (see links page). The responses are following my original letter.
Hi everyone!
A different query (?) for you Infrared film users and knowledgable people.
I'm working on my PhD, looking at the ecology of beachworms in Australia. These guys are big (up to 1.5 meters long, approx 5 mm wide). No-one seems to be able to work out where they live in the sand (ie just below, or down deep), because they are very mobile through the sand, and don't leave holes behind them. Digging them up just doesn't work!
Anyway, to cut to the chase, I'm going to keep them in a thin tank, and want to take regular photos of where they are. The thin tank is so in theory with a light behind, i should be able to see the worm in the tank, and where it is. I'm worried about whether the light will effect them, so was also planning to try IR film, with no light, hoping it would pick up the differnce in the sand with the worm, and the sand that didn't.
Would this work? Am i barking up the wrong tree? If it would work, can anyone give any suggestions about using the IR film, and what type of film to use.
Thanks in advance,
Matthew
use the B&W infrared film from kodak and rather than filtering your camera lens filter your flash instead, this will make the light virtually invisible (to human eyes that is, it might be blinding to the beach worms) just make sure that you position your light in such a way that you don't get a reflection from the lightsource in the glass wall of the tank.
Would some kind of smallscale sonar or radar work better for this purpose?
However, I have never seen the results from HIE with a flash being fired through sand. I hope HIE does the job for you. The usage of sonar will not work though. Sonar is an audio frequency and does not come under the light spectrum. I'm not too sure about radar, but as far as I know, Kodak HIE is sensitive to both IR as well as UV so the usage of a red filter is a must if you are outdoors. Advice: when taking photos with the flash, turn off all the lights in the room. This way, any surplus light (UV and IR) from foreign sources will be eliminated. Also, ensure that no heat sources are near the camera/film which will fog the film.
Hi Matthew. When you build your tank you also need to consider the type of glass used. I know there are differing characteristics for light/IR/UV trasmission especially with tempered glass.
Also, just what dimensions are you planning? Very thin I suppose. Something like an ant farm.
But how deep is deep enough for the worms to burrow?
Then you want to take a picture from the side, through the glass/sand/worm/sand/glass layers?
Radar might work. They do make a 'sled' type device for archaelogical underground non destructive exploration, but I do not know if it can find objects small as you described, or very absorbent of radar (alive/ wet things).
Try NASA. If anyone knows how to remote sense something, those guys ought to.
Sounds like you have chosen quite a task. Good luck, keep us informed.
To clarify, my suggestion of either SONAR or RADAR or perhaps even ultrasound does not involve photography. And is there no way to install a tracking device?
It seems to me that using a thin tank may possibly influence the beachworms behavior since you are essentially restricting the beachworm to two dimensional travel whereas in the real world the beachworm obviously lives and travel in three dimensions. Or perhaps even in four dimensions if it turns out that the time of day or phase of the moon, or high and low tide, etc. influences the depth to it burrows and the range it inhabits.
Regular glass has poor IR transmission qualities. 0.375" glass will only transmit about 60% of the energy in the 800 - 900 nm range. Lexan is a little better, but not much. I'm assuming that your thin tank will be filled with sand, right? If so, the sand will act as an opaque filter as you try to back light the tank with IR energy. Ultrasound seems to be the way to go. X-ray or n-ray might also work, but I don't know how dense your worms are relative to the surrounding sand. Talk to the Medical Imaging people at your local hospital and perhaps to a geologist. Interesting question. (I'm wondering how the catfish 'round here would respond to bait like that!)
I do not think that normal IR film is sensitive to thermal wavelengths of infrared radiation. Ideally, with the right type of infrared film you can take a photo in the dark, and the film will record temperatures. This film is used to trace overheated power lines in distribution centers, and to show heat loss in buildings. The problem here is the normal body temperature of the worm vs the ambient temperature of the sand. There might not be enough contrast.
I think normal photography will be difficult as a few cm of sand will probably block most of the light. A flash large enough to shine through the sand (in effect showing shadows of the worms) would probably toast the critters.
If the tank was thin enough to see the worms in, it might be thin enough to modify their behavior as well.
Radar will be very difficult to use if the water content of the soil is above 20%. The water forms a reflective/absorbtive plane and the radar will not pentrate well below that plane. Optimum soil moisture for ground penetrating radar (GPR) is 8%. Also, GPR signal processing is not trivial. We look for buried landmines using non-contact GPRs(for obvious reasons)and imaging any type of plastic mine is very, very difficult because of the lack of reflectivity giving a small radar return. I would be skeptical of the ability to image animals as they are organic, made up of a great deal of water, would absorb the radar energy (rather than reflect), and would generally just blend into the background.
As for IR, I would recommend that you try and get an IR video camera. I use both an 8-12 micron and a 3-5 micron camera and you can see into soil quite well with these cameras. The microbolometer (uncooled)type cameras will not be sensitive enough for this type of imaging. You will need a cooled image sensor. I would suggest calling Mike Mays at Mitsubishi (714-236-6163). He may be able to rent or lease one to you or may know where you can rent or lease a camera. They are very expensive ($57,500 or more without lens) so unless you have that kind of budget, rental or leasing would be the only way to go. You will need a 4.0 micron cut-on filter to eliminate reflected IR for the 3-5 micron camera. An 8-12 micron camera would not need a filter. Mitsubishi only makes a 3-5. 8-12 micron cameras are hard to come by at the moment. Flir Systems has a new one but it is in the pre-production stage.
You could illuminate the tank with standard tungsten-halogen lights, and after about 1 hour of heat up time, you should be able to see up to 4-inches deep into the soil or sand.
Thanks to everyone for the reponses!
Just to clarify a couple of things:
1. I have and are considering the effect this type of design would have on modifying the worms behaviour - The results from this (if it works!) would be followed up with field observations and manipulations as well. This is only one small part of my PhD!
2. While I'd love to use an IR video camera, like was mentioned, these are hugely expensive, so maybe renting would be the way to go (and this would allow for a thicker tank)... But I've yet to find someone in Australia that has this sort of equiptment! I'll keep looking!
3. The worms are aquatic ectotherms, which means their body temperature is the same as the medium in which they live. Temperature differences would not be seen. What I am hoping is that there would be a density difference in the sand where the worm is, and would show up as an outline of the worm.
4. Dimensions aren't finalised yet, but something in the order of 1 meter x 1 meter x 30 - 50 millimeters (although, I'd love to go as wide as 100 - 200 mm). These will depend on the outcome of some trials I'll do with smaller tanks, and juvenile worms.
5. Yes there are a heap of problems with this idea, but the only way to find out if it would work is to try it!
6. As far as tracking the worms goes, that would be brilliant, but again, finding the technology (and at a resonable price) is proving difficult. If I could get a small and powerful enough transmitter, I think it would work well, as it could be inserted (injected?) into the body cavity of the worm. If anyone knows of anyone who has done this, or where to get such a transmitter, I'd welcome any tips here!
7. The comments on the transmitting qualities of glass are something I hadn't fully considered.. I will have to think about this when I'm building the tank.
I'll let people know how it all turns out! If there are any more brilliant suggestions, feel free to respond!
Thanks again everyone,
Matthew
Perhaps you're using the wrong spectrum. Given that they're ectotherms, I doubt you'll see much.
What do they eat? Most beach creatures are detreitovoirs (sp)? Maybe you could spike the trash with a flourescent dye, then hit them with ultraviolet once they had absorbed enough dye to fluoresce. You use a Wratten yellow filter on the lens to keep the UV out of the film. You'd need to use either glass or special UV transparent acrylic on the clear walls, since normal plexiglass absorbs UV. In a dark room, the only only light hitting the film plane is the visible flourescence from the subject. This would work either with film or video.
Other possibilities: tag them with radionuclides - generally frowned upon these days due to disposal issues. Magnetic Resonance Imaging
UltraSound. The medical imagers doctors use to look at infants while in the womb might work through all that wet sand.
As a tracking device, you might want to look into those shoelaced on jobbies they use for huge crowds of runners like Marathons. The actual device is rather small, just the packaging is large enough to tie on.
Also you could use one of those alarm tags the stores use to prevent theft. With that, you could tell where in the tank your worm is. They are not very accurate, but could be used in a 3D array of sensors to get a clue where the thing is.
Then you could probably give it the Ultra sound to see more.
I find it very intriguing, but don't really have any more 'Photo' ideas for you.
Let us know what you work out. BTW do your worms react to Ultrasound?
HEY!! How about a dab or radioactive dye on it's back/belly/side/whatever. That'd probably glow through the sand enough to capture on some sort of film eh?
Later.
What about feeding the critters a radio-labeled food substrate and then finding them that way?
IR film is not sensitive to thermal wavelengths, i. e., you need a source of light, and you will record whatever is transmitted through and reflected on your sandbox. I would wager that sand is about as opaque to the near IR as it is to visible light (it's basically rock, right?). Since you need the light to go through the sand, I don't think you will be able to form an image. You need something that penetrates your medium. Try to find a transmission vs wavelength charts for sand (plus water), if such a thing may exist, and work from there.
The answer about the IR opacity brings to mind a possible solution to your problem: can you substitute a less opaque medium for the sand. Also a possible problem: How do your beachworms regulate their body temperature? Is their skin surface temperature so different from the surrounding sand that the difference would register?
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