Comments

Author Comment Last activity Moderation
cfastie "Hi jeffalk, Thanks for pointing out that the PM10 index includes all particles smaller than 10µm. If that is true, you are correct that PM10 shoul..." | Read more » almost 3 years ago
cfastie "If a device based on a Plantower sensor includes hardware that allows either live numerical display or data logging, it can be a very useful tool. ..." | Read more » almost 3 years ago
cfastie " Writing data to eeprom will work with the limitations you outline. Adding a microSD card module and 128 MB SD card costs less than $2.00. Adding..." | Read more » almost 3 years ago
cfastie "Thanks, I have pinged the editor. The views on this research note have doubled since December. I wonder what they would be if the link had been co..." | Read more » almost 3 years ago
cfastie " I just noticed that Limor Fried wrote an article for Make Magazine in January citing this research note and using one of the images. An editor ask..." | Read more » almost 3 years ago
cfastie "A full spectrum camera is one that has been converted to capture NIR by removing the IR cut filter. This filter which is present in all standard ca..." | Read more » almost 3 years ago
cfastie "I don' t know what a "dedicated IR camera" is. You can use an appropriate red filter on a full spectrum camera to capture mostly NIR in the blue ch..." | Read more » almost 3 years ago
cfastie " A red filter used to convert a full spectrum camera (IR cut filter removed) to an NDVI camera must pass red light and NIR light but no blue light...." | Read more » almost 3 years ago
cfastie "Subtracting the blue channel from the red channel is a good first step for correcting for contamination of the red channel with NIR. With one parti..." | Read more » almost 3 years ago
cfastie " One photo every 50 shots might be sufficient. It depends on how much the light changes during that time (5 minutes?, an hour?, a day?). You might ..." | Read more » almost 3 years ago
cfastie " You are correct that your multi-day observation will present some problems. It is possible that doing a custom white balance on each day will comp..." | Read more » almost 3 years ago
cfastie "These are really nice bee images. If your goal is to make a seamless composite, the free Microsoft ICE (Windows only) will stitch the photos into a..." | Read more » almost 3 years ago
cfastie "The primary advantage of dual band filters is that they pass much narrower bands of wavelengths than red or blue filters (which also pass NIR). Th..." | Read more » almost 3 years ago
cfastie " The simplest modification to make the sketch save to SD card once per minute is to change the line: if (logData == 1) // wr..." | Read more » almost 3 years ago
cfastie "A few different cameras were used to take those photos. Most of the cameras were Canon PowerShots. I think all of the photos were saved by the came..." | Read more » almost 3 years ago
cfastie "Performing a custom white balance on a blue-filtered NIR camera fools the camera into exaggerating the brightness of the red channel. The red chann..." | Read more » about 3 years ago
cfastie "It will always be difficult to know for sure to what degree the red channel is contaminated by NIR. It might be worthwhile making an estimate. For ..." | Read more » about 3 years ago
cfastie "Although the absolute values you computed for NDVI are lower than they should be, it appears that your process is successfully discriminating betwe..." | Read more » about 3 years ago
cfastie "Liz, it's great to know that you (or I guess your Mom) were well coiffed in the 80s, although I regret that you did not include photographic eviden..." | Read more » about 3 years ago
cfastie "You are correct that both red and NIR pass through the red filter (Rosco Fire # 19) and both are captured in the red channel of the photograph. It ..." | Read more » about 3 years ago
cfastie "Leslie, I will lend you anything you need. Tell me about your HEPA setup. You must already have a 5V Arduino, so all you need is three DuPont wires..." | Read more » about 3 years ago
cfastie "Thanks Nick. It's good to know about the duplicate sensors. That's an intriguing engineering decision. Chris " | Read more » about 3 years ago
cfastie "This photo does not look like it was taken with a mobile phone (the image quality and dynamic range are too high) and it does not look like a CD or..." | Read more » about 3 years ago
cfastie "The field evaluation report linked above includes 78 graphs comparing the results of a Purple Air sensor with a $25k GRIMM optical particle counter..." | Read more » about 3 years ago