One-shot TriColour IR?

[Stefano]

Today I tried my ZWB2 filter alone to take some UV/IR photos, ad I also took photos of the solar spectrum with a diffraction grating.

 

The equipment is the usual, full-spectrum Canon EOS M and Soligor 35 mm f/3.5. Image white balanced in-camera.

 

Here's one:

 

You can see IR on the left, and UV on the right, with the 400-700 nm gap in between.

But look closer at the IR section:

 

There is an approximate RGB "rainbow", with blue for the longest wavelengths, green for the medium ones and orange for the shortest. Although this is only the IR band passed by the ZWB2 filter (UG1/U-360 equivalent, so about 700-800 nm), can we in some way separate those RGB components and use this technique to take one-shot TriColour IR images in the 700-800 nm band?

[Andy Perrin]

Isn't that what we do anyway if you take a shot with that filter on the camera? You do get colors in the image in that range. Since this IR rainbow is in the same sequence as the normal rainbow, that means it's pretty much already a one-shot TriColor?

[Stefano]

Yes, in a way it already is. It looks like if I stack this filter with a Hoya R72 and I take a photo of something I should be able to separate three bands between about 700 and 800 nm. The problem is that this isn’t perfect, and for example at the shortest wavelengths I have orange instead of red, so I should “purify” that channel.

[dabateman]

Yes I think Bernard talked about this.

We were using either ZWB2 or Zwb1 with R72 to get 700s. Then BN850 for 800s and Lp950 for the upper 900s.

That works.

[Stefano]

David, in this case the idea is to use ZWB2 + a UV blocker to have something like 700-730 nm, 730-760 nm and 760-800 nm, very roughly. So it's only one filter to have colors in the 700-800 nm band.