Broadband backdrop material?

[Guest]

I have a small area setup for shooting multispectral image sets. In the simplest of terms, its not much more than a box with an open side for shooting through, and an opening in the top for the source light. I currently have it lined with aluminum foil to prevent unwanted off-target fluorescence (particularly for UVIVF images). This also helps to contain and increase ambient UV around the subject, which may also help a little with exposure times (though I understand, reflected UV is much less energetic than direct - but I figure every little bit helps).

 

I'd like to try changing the 'backdrop' - instead of using a reflective surface, I'd like it to be blacked out. Unfortunately, I can't seem to find a good material which absorbs all the way from UV, through VIS, and into IR. IR seems to be the difficult one here of the three bands. I have found that some synthetic materials do a good job absorbing IR, but I don't know yet which/what kind.

 

Notice how some of the material is black in IR (e.g., the handle straps), while the rest is white/reflective.

 

Just wondering if anyone knows off-hand just what kind of material is a good IR absorber - and which is, ideally, also a good aborber in VIS and UV at the same time?

[OlDoinyo]

Carbon black (and colorants based on it) are good IR absorbers. Many other "black" dyes and pigments are actually deep blue or green and do not absorb IR. Carbon may do less well in UV, as things such as asphalt paving can appear pale. A mixture of carbon-based black pigment and red dye should do the trick, in theory, but material pre-treated with such a mixture may not exist.

[Andrea B.]

Finding a good UV backdrop in black is an interesting problem. I've used at various times: an artist's canvas painted black, black foamboard, large black books, a black metal music stand and some black velvet textured cloth.

 

All of these have mostly worked, but there always little problems. The canvas or books are too textured and make for distracting, non-smooth backgrounds. The foamboard and velvet cloth have reflection or discoloration problems when used with UV-flashes or torches. The music stand is not easy to use as a backdrop and also can be reflect-y. So I typically have to resort to some tricks in the editor in order to smooth out textures, reflections and discoloured areas.

 

There is one option which I have never priced: Permaflect targets with 5% reflectivity

These are diffuse, stable under UV and do not fluoresce. In other words, ideal.

But I am simply afraid to ask for the price !!!!!

[Cadmium]

I remember from some material tests years back that black rubber sheet was very black in UV, however I have never actually used it for a background.