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Author Comment Last activity Moderation
mathew "the fluorecence looks the same even when the laser heads into the sample at a slightly different angle-- is the light path critical? I figured it o..." | Read more » over 8 years ago
warren "Actually, kind of amazing -- for the Creative webcam ones, not enough laser was actually reflected into the spectrometer to get the 405nm peak... c..." | Read more » over 8 years ago
warren "Oh, edit: the Creative had a wider than usual slit -- maybe 1.25mm or so. So maybe the clipping in the blue channel wouldn't be as bad with a littl..." | Read more » over 8 years ago
JSummers "I hate to say it, but it looks like your laser peak at 499 nm looks like it was truncated, meaning that your fluorescence intensity is 25% of what ..." | Read more » over 8 years ago
mathew "What happens if you unscrew the lens on the laser and put it in front of the LED? can you concentrate the light to make a brighter point? " | Read more » over 8 years ago
warren "Hi, Livio - I was so fascinated with your post -- where exactly did you collect a sample from, and was it soil? Water? " | Read more » over 8 years ago
WhiteRabbit "I found this: http://www.vernier.com/products/sensors/col-bta/ which is interesting because unlike other low-cost spectrometers/colorimeters its s..." | Read more » over 8 years ago
warren "Wow chris the barcode scanner filter idea is great!!! " | Read more » over 8 years ago
cfastie "The Public Lab desktop spectrometer is quite capable of making a spectral graph of sunlight reflected from grass. The curve will differ from the pr..." | Read more » over 8 years ago
WhiteRabbit "Here's a write-up that I'm finding quite helpful: http://publiclab.org/notes/nedhorning/11-01-2013/why-a-red-filter-should-work-well-for-ndvi Eyeb..." | Read more » over 8 years ago
WhiteRabbit "Sounds like gel filters would be tricky at best, so I guess ixnay to that. How about this one? http://www.ebay.com/itm/Optical-Interference-Filter..." | Read more » over 8 years ago
stoft "Good observations -- but why use a CFL which has poor SNR for wide-band averaging because the spikes prevent using higher light intensities for bro..." | Read more » over 8 years ago
cfastie "I have not seen a cheap filter like Rosco that is truly a narrow band pass filter. It might be possible to combine filters to get a fairly narrow t..." | Read more » over 8 years ago
WhiteRabbit "Cool! Awesome post. I suppose it's wishful (and probably foolish) thinking, but given the the low price of a filter swatch book and the seemingly..." | Read more » over 8 years ago
cfastie "A filter switcher is a viable solution, especially for small cameras. Cameras as large as Powershots might require a big, precise device in front o..." | Read more » over 8 years ago
WhiteRabbit "Thanks, Chris, for your thoughtful and very informative post. If I'm reading it right, perhaps using two monochrome cameras, each with the appropr..." | Read more » over 8 years ago
cfastie "It should be possible to distinguish between stressed and non-stressed lawn grass using NDVI. I suspect that the $900 FieldScout performs more or l..." | Read more » over 8 years ago
WhiteRabbit "Interestingly enough, I did just now find this $889 turf grass color meter which does, indeed, use NDVI! http://www.specmeters.com/nutrient-manage..." | Read more » over 8 years ago
WhiteRabbit "Thanks for the links. Supposedly grass also changes color as the soil loses moisture (IIRC, it becomes less green and more blueish?), and people c..." | Read more » over 8 years ago
warren "I think a lot of the challenge of using an Infragram camera well is the need for comparison. Comparing an area treated in one way with a "control" ..." | Read more » over 8 years ago
ygzstc "Thanks a lot Jeff! " | Read more » over 8 years ago
warren "I think i found the data on Yagiz's Spectral Workbench profile, and I made a set: https://spectralworkbench.org/sets/show/1369 Embeds don't seem t..." | Read more » over 8 years ago
straylight "ah yes, good thinking. well done again on your work, a very well written research note as well. stu " | Read more » over 8 years ago
ygzstc "Thanks Stu... I just wanted to see if added sugar is detectable first. If yes, you can may be measure the sugar levels during wine making process a..." | Read more » over 8 years ago