response:9293
response:9293


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 » almost 11 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 » almost 11 years ago