It makes sense, but the only key to IR sensitivity there is to filter OUT what you don't want - and to capture pure IR, you have to filter the visible light. I think it would be... very difficult to have four layers and retain sensitivity.

I've got a Fuji IS-1, which is the Ir-sensitive model of bridge camera; it has an IR filter and I imagine using HDR techniques I could combine IR and visible light using that.

Interesting discussion re IR etc. No doubt there are many potential applications for such a capability, in addition to purely artistic pursuits. It would be interesting to hear from anyone who is actively using the existing IR functionality, perhaps for scientific purposes?

As for the artistic element, I have heard it said (by some of my northern colleages) that an equivalent experience may be had via the copious application of Newcastle Brown - especially on these clear, cold nights.

Kind regards,
JA

Pure IR is used for forensics and similar; it's not a Sigma but I'll share some IR photographs from the IS-1 when I've had time to sort them out. The black skies (in daylight) are particularly nice, but I'll see if I can make some of the "scientific" captures work.