Infrared with the M system

Fedia Le Grill wrote:

Wow if this graph is true I want a canon 350D immediatly :

https://www.researchgate.net/figure/Spectral-sensitivity-of-unfiltered-Canon-350D-sensor_fig1_229046541

the peaks in red first, then green, then blue seem distinct enough to produce a real three-color image only with the 700 to 1000nm IR spectrum !

The thing is I have a canon 1000D full spectrum (wich is only 3 years more recent than the 350D, it has a different sensor though...) and I never noticed that they were any color variation in the tones it produced when I use it with a 720nm filter....

Does it mean that the that objects reflecting IR refelect all IR wavelengths the same way ? That it is impossible to extract Three primaries like for exemple 700nm, 800nm and 900nm since all those wavelengths are reflected the same way ?

I did notice though that when I use a 720nm filter on the camera and I add a GRB3 filter that cut the longer IR wavenlegths the image color slide towards Red. I suppose that If I added a 850nm filter that cut the shorter IR wavelength the image color would slide toward Blue or deep violet. I dont have this filter just now, but I ordered it.

It looks like the 3 color curves were 'normalized' for that 350D spectral chart so that their peaks are at the same height in the chart, and doesn't reflect their 'true' responses relative to each other.

Otherwise the chart looks similar to other Canon cameras and those from other brands.

The distinct 'red' peak is around 600 nm, which is why a 590 nm 'orange' filter gives distinct (swapped) colors, and a 550 nm filter or other yellow filter like a Tiffen deep yellow #15 gives even stronger colors.