daniel hayduk Posted January 3, 2005 Share Posted January 3, 2005 I am doing a school physics project on infrared photography (don't you love it when you can put enjoyment into something boring) and I need to know the maximum wavelength (nm) that the CCD on my D100 is capable of recording. Since the D100 can record IR, it is clearly above 700 nm... but how far does it go? As far as I have tested, it cannot record things in MWIR (Mid Wave IR) which is the thermal zone (3000-8000 nm). Does the CCD record SWIR (Short Wave IR - 1400-3000 nm) or just NIR (Near IR - 700 - 1400 nm) which I know it can? If it doesn't go beyond NIR how much of NIR can it record? I have a Hoya R72 filter, so it does 720 nm... <br><br>I would really appreciate it if someone could help me out. The project is due on January 5 - so please hurry!<br><br>Thanks,<br><BR>/daniel<br> Link to comment Share on other sites More sharing options...
walterh Posted January 3, 2005 Share Posted January 3, 2005 Daniel I do not have the answer but realize that if you mention the filter you may take images with a lens? In this case the transmissive properties of the lens as well as sensitivity of the sensor need to be known. Too bad that you are in such a hurry- would have been more relaxed if you would have known about this already before the holidays .-) Link to comment Share on other sites More sharing options...
matt_chamberlain Posted January 3, 2005 Share Posted January 3, 2005 Is the D100 modified? The internal high-pass (IR-cut) filter will be your limiting factor if it has not been removed, and the IR opacity of this filter will determine which frequencies even reach the CCD. The IR sensitivity of your D100's CCD will of course be into much longer wavelengths than this filter allows it to see. If I were you I would try to find out the exact specifications of this IR-cut filter and go off of those numbers. Also, you might try finding some narrow-band IR sources like remote controls and stuff that you can find out the exact frequency range and use those in experiements (take a photo of the emitters in an otherwise dark (to you and the CCD) room. Just some idea.... I'll continue to think on it. Link to comment Share on other sites More sharing options...
matt_chamberlain Posted January 3, 2005 Share Posted January 3, 2005 Borrowed the following from <a href="http://www.northcountryradio.com/Articles/irfltr.htm">here</a>. <br><br> A low cost IR filter can be made from an exposed piece of color negative film. Using a piece of Kodak's Kodacolor negative film, ASA100 speed, exposed to ordinary flourescent light for 5 seconds at normal office or room ambient levels, and developed normally in C41 chemicals (The standard everyday Minilab process method) the developed film becomes the filter material. Data on optical transmission follows:<br><br> Wavelength / Approx. Transmission %<br><br> <700 nm / below 3 percent<br> 700 nm / 3<br> 750 nm / 10<br> 800 nm / 70<br> 850 nm / 90<br> 900 nm / 88<br> 950 nm / 87<br> 1000 nm / 83<br> 1050 nm / 80<br> 1100 nm / 75 <br><br> The transmission characteristics are good for IR leds, laser diodes, CCD cameras, IR tubes and such operating in the 800-1100 nm near IR range. The film is cheap and readily available and you might try the blackened ends often found on a roll of the film after processing. The film however is delicate, scratches easily and is not moisture resistant, but it might be sandwiched between glass or plastic for protection. It might be useful as a first try before purchase of a more expensive material. Link to comment Share on other sites More sharing options...
fourfa Posted January 3, 2005 Share Posted January 3, 2005 http://www.naturfotograf.com/irstart.html Link to comment Share on other sites More sharing options...
vivek iyer Posted January 3, 2005 Share Posted January 3, 2005 I fully agree with what Matt said. I know that D70 with an ultra thin BG filter does let in IR > 1000nm. I use a very dark IR filter (cut off >1000nm) for IR photography. Link to comment Share on other sites More sharing options...
daniel hayduk Posted January 3, 2005 Author Share Posted January 3, 2005 Wow, thanks for all the responses everybody! No it is not modified, so I guess the real question is what the high pass IR filter permits (that's what I get for posting when I'mm tired!) - and I haven't been able to find the answer. My impression is that for IR most lenses let everything fly, they just have UV protection. I could be wrong though! <Br><Br> Thanks again, <br><br> /daniel<br> Link to comment Share on other sites More sharing options...
berg_na Posted January 4, 2005 Share Posted January 4, 2005 The CCD image sensor in the D100 is fabricated in silicon, so its cut-off wavelength is 1100 nm (silicon is basically transparent at longer wavelengths), the CCD response in the NIR drops off rapidly above 900 nm. Silicon is not suitable for SWIR detection, you'll need sensors fabricated on materials with narrower bandgaps like InGaAs (1680 nm cut-off wavelength). Sorry for the late response, I hope you'll do well on your project. Link to comment Share on other sites More sharing options...
daniel hayduk Posted January 4, 2005 Author Share Posted January 4, 2005 Thanks Berg! <br><Br> /daniel Link to comment Share on other sites More sharing options...
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