Why does CRI matter if colour temperature and hue are fixed? - if everything is only RGB anyway

Hi all,I (think) I understand the concept of Colour Rendition Index, but I feel like I'm missing a part of the puzzle since it contradicts other things I know (RGB).If I understand correctly, CRI is a metric for the "completeness" of the spectrum of a light source. A light with a poor CRI rating would miss certain frequency components of the spectrum and therefore render these colours improperly.Why does this matter though, as long as the light has the correct colour temperature and hue? It is my understanding that any light with the same colour temp and hue would map similarly to the RGB-space. Since camera's, monitors and even our eyes work exclusively with RGB, why does it matter if certain colours are missing from the spectrum, if the totality of the light maps properly and evenly to RGB?Concrete example:I photograph a yellow banana under three lighting setups.1. Daylight: 100% CRI, all frequencies represented properly:The yellow wavelengths of the light reflect off the banana, these yellow wavelengths excite the R and G subpixels of my DSLR evenly, perfect picture.indoors, at night, using a low CRI light but it has the same hue and colour temperature as daylight.It's CRI is poor because it doesn't have enough yellow in it's spectrum. It would have to make up for it with extra red and extra green, otherwise the hue and colour temperature would be off.The green and red wavelengths reflect off the banana, less so than the yellow wavelengths but they add up to the same total. These green and red wavelenghts excite the R and G subpixels of my DSLR evenly, perfect picture.Extreme example: a combination of a pure RED, pure GREEN and pure BLUE light. So 3 lights, only 3 wavelengths. To our perception they add up to white of the same hue and colour temperature as setups 1. and 2.This setup would have a very poor CRI, since only 3 distinct wavelengths of the spectrum are represented.The red and green get reflected by the banana less so than the yellow wavelengths but they add up to the same total. These green and red wavelenghts excite the R and G subpixels of my DSLR evenly, perfect picture even though there never was any yellow light.What is wrong with my reasoning in 2. and 3. ?Am I wrong in assuming that a light with poor CRI could still have the correct overall colour tone? via /r/photography https://ift.tt/2wkl6Qx