Hi Mario,
White balance could be a problem. All of those preset white balance settings and the results from auto white balance will be very different from the results if a custom white balance is done as described here.

If the camera can save camera raw files, they can be white balanced after they are taken. If only jpegs can be saved, then it is difficult to get good NDVI results without custom white balance.

Here is the histogram of foliage in your photo:

Note that there is not much difference between the values in the red and blue (NIR) channels.

Here is the histogram for foliage in a photo which can be directly converted to NDVI (from this note):

Note that the blue (NIR) values are about eight times larger than the red values.

To convert your photo into a photo that can be converted to NDVI, you could try to adjust the color balance so foliage was a blue like in the photo above. I have never had much success doing this. The NDVI image is never as meaningful as when a proper custom white balance is set before the photos are taken. You might be able to find a clever way to do it.

Chris

Can you tell me whats the red filter used for....just taking off the infrared filter and getting R G B IR channels and separating those channels later would work the same right? .The channel separation can be easily done in Fiji App. I am also wondering in your case in RGB spectrum, the Red would be Near Infrared, Green would be Red and Blue would be Green right after adding red filter.Correct me if i am wrong. Can't a normal RGB camera take 4 spectrum after removing IR filter?

Look forward to your response.

With certain red filters replacing the NIR cut filter, instead of red, green, and blue channels, you get red+NIR, NIR, and NIR channels. Without adding the red filter, you get red+NIR, green+NIR, and blue+NIR.

Chris

Hi sorry about my english I from Uruguay and just bought a phantom 3 pro with NIR camera conversion. I've the same confusion about the channels of my NIR camera is capturing. The people who sold me told me that the modification was remove NIR filter and configured the software to not broke the hardware, that correct?. I want this to generate NDVI in diferents crop and then analize them.

That is a image captured by my drone. I did a color histogram in fiji and the results were:

The sellers tell me that there are lot of lut filter who do NDVI with the images captured like this, but I was reading a lot of tutorials on forums and couldnt know who lut is better for diferents things. ND in red channels seems too near to 255, and that thinks its wrong. I was worked with GIS programs to separte bands, but i don`t know wich band is NIR, Red, Green or blue. Thanks for help

I can't tell from the photo what kind of filter your camera has. My guess would be that it is a blue filter, so the red channel would be mostly NIR and the blue channel would be mostly blue. But I can't be sure. Do you have a link to the camera or lens you have? Do you know what white balance settings were used in your photo? If you can't do a custom white balance, taking photos which can be directly converted to NDVI will be difficult. Regardless of filter, both the red and blue channel will have to be exposed well (not over-exposed like the photo here) to get good results.

Chris