| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| cfastie | "Is the levels stretching you are referring to the same thing as histogram stretching? If so, it should be high priority. If the look up table feat..." | Read more » | about 10 years ago | |||
| warren | "Corrections made re: order of operations, thank you Chris for a sharp eye and a clearer memory of how to do basic arithmetic! And you said you coul..." | Read more » | about 10 years ago | |||
| warren | "Mathew only sent me one raw image: " | Read more » | about 10 years ago | |||
| cfastie | "It looks like you've done a good job matching the NDVI index from the two cameras. It's hard to evaluate the meaningfulness of the NDVI images beca..." | Read more » | about 10 years ago | |||
| nedhorning | "I think it might be possible to work on a simple calibration process that could be used to get decent NDVI values. I don't think there is much a us..." | Read more » | about 10 years ago | |||
| warren | "...the plant pixels will have the biggest values for both R and B and the difference between them is therefore likely to be bigger. Yeah, the idea..." | Read more » | about 10 years ago | |||
| PeeBee | "Thanks cfasie. I understand now the exposure issue you raise. But you seem to assume the different exposures are an unknown, which it strikes me ..." | Read more » | about 10 years ago | |||
| cfastie | "To compute NDVI, you have to know the relative amount of light in a visible and an NIR band being reflected from plant leaves. The difference betwe..." | Read more » | about 10 years ago | |||
| air_maiden | "I too am interested to see whether a non-modified camera and a camera with the IR filter removed can be used to calculate NDVI. Could you please cl..." | Read more » | about 10 years ago | |||
| cfastie | "That's a really clever idea, and I think it might work. However, it assumes that: The photos must be simultaneous if anything in the scene is cha..." | Read more » | about 10 years ago | |||
| PeeBee | "Thanks cfastie. I don't think I understand the need for the Wratten filter. My understanding is: A camera with just the IR filter removed (i.e. n..." | Read more » | about 10 years ago | |||
| cfastie | "I see what you mean when you say that the difference between the blue and red channels is correlated with the presence of plants. Your monochrome i..." | Read more » | about 10 years ago | |||
| warren | "In short, while you've clearly shown there is IR in all 3 channels, there is still a reasonably good signal/noise ratio difference between 2 channe..." | Read more » | about 10 years ago | |||
| warren | "Thanks Chris, but I'm not sure I agree that we're just seeing brightness due to infrared. I'm not saying this is NDVI -- it seems to work in the re..." | Read more » | about 10 years ago | |||
| cfastie | "If you have two cameras, and your goal is NDVI or false color infrared, the best way to get what you need is one unmodified camera and one with the..." | Read more » | about 10 years ago | |||
| PeeBee | "I am new to this field, and am busy trying to mod a Mobius by removing the IR filter and adding a blue (red remove) filter. I have made a side by ..." | Read more » | about 10 years ago | |||
| cfastie | "More tests are definitely merited. First, I was assuming that Carl was using a Rosco blue filter, and my original conclusions were based on that. ..." | Read more » | about 10 years ago | |||
| warren | "Hey just bumping this back up -- using Infragram.org Mathew L and I did a quick re-try on this, using the expression ((R-B)/(R+B))*-1 in the Hue fo..." | Read more » | about 10 years ago | |||
| cfastie | "There might be some math magic that will help, but that is beyond me. It will be important to check that whatever math is done, the resulting index..." | Read more » | over 10 years ago | |||
| warren | "I wonder if, although the absolute NDVI values seem not to be helpful, the images may still be able to distinguish between healthy and unhealthy ve..." | Read more » | over 10 years ago |