Why Multi Spectrum Photography Is So Rare

Very few people shoot infrared, many fewer yet shoot full spectrum, and practically nobody shoots UV.  There are many reasons for this, I believe.

Equipment

Cameras

1. While technically possible, shooting Full Spectrum or Infrared without dedicated, converted (by replacing hot-mirror) camera is super-painful.  Using cameras without conversion, exposures are extremely long, mandating tripod and excluding scenes with any movement, and good results are much harder to obtain.
2. For good results, the camera must have a very high dynamic range, very low noise, and great shadows recovery.  Much more so than for visible-only photography.

Together, (1) and (2) mean that one has to take a very expensive camera and pay several hundred dollars... to very significantly damage its resale value, to say nothing of automatically cancelling the warranty.  While it is certainly much cheaper to buy an already-modified camera second hand, high-end modified ones become available very rarely.  Thus, most people experimenting with IR choose to use highly sub-par cameras.

Lenses

Most lenses tend to have one or more issues of variable severity with IR, and absolute majority of lenses have terminal issues with UV.  There are no cheap lenses that perform well in UV.  There are some non-exotic lenses that do well in IR.  A lot fewer of them do well in Full Spectrum.  Finding these, both due to their rarity and the lack of reliable information on the web, is hard.  Most people dabbling in IR thus choose to use whatever lenses they have (usually inexpensive zooms, which are, with few notable exceptions, the worst performers in IR).

Overall Equipment Choice Impact

Thus, most people experimenting with IR end up using very poorly suited (to this task) cameras AND lenses.  Sadly, the negatives don't cancel out, but, often, multiply.  The bad lenses will likely produce lots of blur (especially in the periphery), lots of chromatic aberrations (a lot of it not fixable in software), veiling flare, and hot spots.  The camera will add insult to injury by generating lots of noise (hopefully without the ugly banding structure, e.g. Canon), and may even focus badly, exacerbating the blur.  Thus, even with perfect pre-exposure technique, results out of the camera are likely to be very bad purely due to the equipment choices.  But wait...

Pre-Exposure Technique

Shooting full spectrum and infrared is quite different from shooting visible, because it's hard to say how things will look by just looking at the scene.  Full Spectrum and deep IR (800nm+) shots will look very bland (compared to likely ideal post-processed version), whereas super-blue (blue + IR), super-color (590nm), and traditional (725nm) filtered results will look nothing like the expected post-processed results, complicating out-in-the-field judgement.

It is very important to know the limitations of one's equipment, including optimal aperture range (and verboten aperture ranges) for every lens/spectrum combination, whether the lens is question can accurately auto-focus in a given spectrum, as well as maximum ISO at which the noise in the post-processed result is still acceptable.

Finally, cameras tend to get the exposure very wrong, and correcting for it is vital (due to expected drastic modifications coming in post).

If any of the above are gotten quite wrong, added to the damage already coming from the equipment, the results can easily be predestined for bit bucket before the image is ever loaded in Lightroom or Photoshop.

Post-Exposure Technique

Most IR exposures require relatively significant post-processing prowess to get them to look great.  I consider myself a relatively advanced Photoshop user, and yet I often struggle to produce acceptable (to me) results from exposures that I am pretty certain should be workable.  The only (partial) exception to this rule is deep IR (800nm+) exposures, which require one to be relatively good in B&W processing, but no more than that.

It is not easy to do a good job post processing even those exposures which are made using top of the line equipment and very good pre-exposure technique.  Adding sloppy post work on top of a badly planned and poorly executed exposure made using inferior equipment is, well, unlikely to please.

Summary

Shooting in FS, IR, and UV is similar to the traditional visible-light photography... in the beginning of the 20th century.  There is a long and complex pipeline of steps to get the final result, very few people have the knowledge and skills to do all these steps well, and screwing any step up seriously inevitably leads to failure.  Fields with this property tend to have few players.  Which is one of several reasons (see my previous post) why I chose it.