Black fabric, or material, that is truely non-reflective

Question

I've got a couple of cases where by necessity I am shooting through glass and I cannot use any of the tricks mentioned as answers to questions like this and this. In both cases, I cannot change the position of the camera (in one application it's mobile and the position changes such that sometimes there is a problem and sometimes not) and there does not exist any kind of (e.g. polarizing) filter that would fit on the cameras in question.

The best solution I have found is to put some kind of black material on top of the reflecting surfaces as that is the one variable I can control. But the problem is that I have not found any kind of black material that is actually completely non-reflecting. I have tried black paper and cardboards, but have found that I could "see" both of them reflected in direct sunlight. I recently went to a fabric store and found the darkest black material they had, of cotton (as stuff like polyester tends to have a reflective "sheen" on it), and of a very fine weave (so the weave isn't large enough to show contrast). But it also had the same problem - at the very edge of where the fabric reflected I could see that the black surface produced a noticeable increase in the white level of the glass. If the fabric isn't completely smooth I can also see noticeable contrast differences in this reflection.

I realized that this makes some degree of sense - even with for example a 99% light absorption rate, 1% of bright sunlight is still quite a bit of light - as much as 10 watts per square meter. Unfortunately fabrics don't usually advertise their actual albedo, and I don't want to spend a lot of money ordering various fabrics only to find they don't work! It's also possible that a material that has an internal structure that isn't parallel to the surface might work but I don't want to spend a lot of time building and fine tuning (for example) a piece of cardboard that has pieces angled up from it.

I was told that certain photographic fabrics or materials might work, but unfortunately they had never heard of this at the fabric store, despite the fact that that was practically all the sold in the entire large cavernous store. It's also not very suitable to try to determine reflectivity under the comparatively (to the sun) dim lights of a store.

In my searching for a suitable material I have read about various things like "flocking paper", fleece, "Duveytyne", velour, and a few other materials, but these were in the context of very dark materials for photography not specifically for reflection elimination, so it's not clear to me if any of them would work. What's my best option for a black material that is as totally non-reflective as possible?

Answer 1

In the lab we use a black flocked paper/fabric to eliminate stray light reflections. That should work as well as the stuff from photographic suppliers, but isn't velvet because that's too likely to shed fibres. Thorlabs sell in most countries and accept credit card orders, though I haven't ordered personal stuff from them (only work materials on account). BFP1 on the page I've linked is the flock sheet, with approximately 1% reflectivity over the visible range, while BKF12 is equivalent to Cinefoil, or even the same stuff.

Whatever material you use, it will perform better nearer to normal incidence than at grazing incidence (i.e. you want it nearly perpendicular to the line of sight).

You also have to take into account the relative brightness of the source of stray light and the subject. You can often reduce significantly the amount of light that can be reflected - e.g. shooting through a car windscreen, black it out apart from a small hole to shoot through, or at least stop direct sunlight entering the car, in addition to using non-reflective material on the dashboard.

Answer 2

The usual photography suspects - materials such as Duvetyne - are meant for reflection control on-set or as backgrounds. The fabric is dark enough that you can use them in conjunction with the inverse square law to pretty much ensure that local lights (and reflections from objects on set) will be well below "exposure black" by the time (or, rather, by the distance) they make it back to your shooting subject. A very high-quality black velvet is even deader, provided that the surface fibres are properly aligned for your purposes (the sides of the fuzzy bits are merely black fabric; it's the canyons between the fibres that does most of the actual hard work). That's good and all, but it's not going to get you to the dead black you want to prevent, say, dashboard reflections in windshield glass. (Well, it could work, but you'd need to brush the velvet to suit the shot, so it's no good for video on the go or for quick shooting.) For that, you need specialty stuff.

There are two problems with specialty stuff. One is that it's fragile, so if it's anything that is exposed and needs to last, it's going to need relatively frequent replacement. Every material that does what you want relies on structure as much as colour to do what it do, and that structure won't stand up to much cleaning. The other problem is that it tends to be on the expensive side. Not "mortgage your house" expensive, just a whole lot more than most fabrics, at around $10 to $25 US per square foot (130 to 300-ish € per square metre), depending on the material. And there is stuff that is significantly more expensive - and effective - still, but it becomes entirely impractical for anything except the innards of cameras and optical instruments - all of the increased light absorbency will be killed by ordinary dust and moisture in minutes. A couple of possible solutions are Fineshut SP and VL Flocksheet, both by KoPro and available at Amazon. (The company makes black, and that's about it. They're the makers of Mosou Black paint as well.) Fineshut sheets are meant to line optical instruments of various sorts, with the SP version being the high-cost-but-maybe-practical end of what you're looking for, depending on budget. Fineshut KIWAMI is the stupid-expensive stuff you really don't want to waste money on. It's the best stuff out there for other uses, but not for your use case. Flocksheet is more of a TelePrompTer-liner sort of thing, which is more or less what you're looking for. Again, they're all fragile to one degree or another, but that's what makes them work.

Another product mentioned here is Cinefoil. Great stuff, but not at all what you're looking for. Cinefoil's party trick is that it's heat-resistant while being pretty darned black. That means it can be used near hot lights. And being foil, it can easily be shaped. Needless to say, that makes it the ideal thing for impromptu light-shaping tools. It's also great for killing reflections from light stands and so forth, mostly because there's going to be a roll or two or three of the stuff in your gear bag or on your tape-and-gel rack in the studio. When it's the right stuff, it can't be beat, but it's not the right stuff for the case you've laid out. It's matte black, but it's not nearly black enough or matte enough. You want something that looks like somebody pulled a Looney Toons portable hole out of their pocket and threw it on the surface you want to get rid of. Cinefoil isn't that. Optical blacks are.

Well, they mostly are, at least. Light them bright enough and crank the exposure up high enough, and you'll be able to shoot them. If you're parked in full sun at high noon and trying to get shots of something at the back of a dimly-lit parking garage, physics doesn't really care about your feelings... or your job. Slightly less than one percent of an awful lot is going to drown out 80 percent of next to nothing. You'd need to make sure that the light doesn't make it to your side of the glass in that case (with shades), to the extent that you can. Black materials can only do so much.

Answer 3

Cinefoil is the typical solution for photographic and film use. The generic name is “black foil” because “Cinefoil” is a brand name.