[Kombisaurus]

Hi Pavel,

You're correct that in order for us to see IR photos, that part of the spectrum must be mapped to visible light.. but that doesn't mean there is a correlation between visible colours and IR colours any more than there is between two different colours in the visible spectrum (ie Green and Blue). So any software IR emulation is really just based on guesswork to provide a similar look to IR. A real IR photo might look completely different.
The reason you see green tree foliage appear as white in IR photos is not because the colour green reflects more IR light, it is because tree foliage reflects IR light. You could park a green car beside a green tree and they may appear identical in a faux emulated IR photo, but completely different colours in a true IR photo.
I remember taking some test IR photos around the house and was very surprised to see that a black jumper I was wearing appeared completely white in the IR photo, while most other black things in the room appeared black. It seems the jumper absorbed visible light yet reflected all IR light.
The emulation software generally uses an algorythym based on how the most common materials seen in IR photography would appear (ie blue skies and water, and green plants, etc). Because as humans we don't really know what colour many other materials are supposed to be mapped to, we just accept them to be correct.

But, does it actually matter if an IR photograph is "true" or not? The reason most people shoot IR photos is not out of scientific interest in IR light, but simply because it allows for some beautiful photographs. If you are happy with the photographs from the software, then that's all that matters in the end.

Personally I prefer the flexibility of using a channel mixer in weird and creative ways instead of a dedicated IR plugin when I'm after a particular aesthetic look. When I shoot IR (which is rare) it's generally because I am actually curious about how the world looks in the IR spectrum, so the emulation is no good.