Xume Quick Release Filter Adapters: Yeah, Magnets!
Screwing a filter to the front of your lens can be a frustrating task. If you've ever wished for an easier way, your wish has come true. Xume quick release filter adapters are one of the most ingenious photography gadgets I've come across in some while. And they do it with magnets. Yeah, magnets!
Digital photographers don't really need filters as often as did photographers back in the days of film. These days, color can be corrected digitally or via in-camera white balance. But polarizers for cutting reflections and neutral density filters to achieve longer exposures are still indispensable in certain circumstances. I wouldn't be caught without both in my camera bag. But screwing a filter on the front of a lens isn't necessarily as easy as it sounds. The fine threads have to be aligned just right and while I'm fumbling with a filter, the magical light I'm hoping to capture may be changing. Rushing the task though risks cross-threading the filter or even dropping it.
Both polarizers and neutral density filters block some of the light from getting through your lens, complicating the job of composing and focusing with these filters attached. I have a Singh Ray variable neutral density filter that can go from about two stops to a full eight stops of density. With it fully rotated to maximum you can't see a darned thing through the viewfinder. Even at the minimum two stops things can appear mighty dark. This not only makes my job more difficult, it can also interfere with the camera's ability to autofocus. It would be great if I could easily and safely go from no filter to filter without messing with screw threads.
Enter Xume quick release filter adapters. Image if you will a typical screw on filter with no glass in it, just the ring. Now carefully slice it in half to form two thinner rings. One will have male threads on it to screw onto the front of a lens, and the other half will have female threads to allow you to stack another filter on top. Now image that the piece that screws onto your lens were magnetic – strongly enough that the other half will stick to it. This should give you a rough idea of what a Xume adapter it, but the execution here is so well done that it almost certainly exceeds what you're imagining.
These patented quick release adapters are precision machined and fit together quite smoothly and solidly. The front ring screws to your filter and the back ring screws onto your lens. The two halves are held together via magnetic force and are machined such that the front ring sits somewhat recessed into a cavity on the back ring. This design prevents them from sliding apart. The only way to separate them it to pull the two apart perpendicularly to the image plane (that is, directly parallel to the lens axis).
If you've ever played with rare-earth neodymium magnets you know the kind of magnetic force we're talking about here. These things are strong. I've done some informal testing and it takes about a pound and a half of force to separate the pieces. That's considerably more than even the heaviest filters. My huge Singh Ray Vari-ND weighs less than three ounces.
The packaging and website for Xume don't spell out what type of magnets these are, but neodymium alloy seems a fair bet. General Motors and Sumitomo Special Metals of Osaka, Japan came up with this alloy of neodymium, iron and boron in 1982. Since then, they've been finding their way into just about everything from disk drives, electric motors, loudpeakers and MRI scanners, to fridge magnets and toys.
The once popular "Buckyballs" magnet toys were recently banned by the Consumer Product Safety Commission here in the United States as a health hazard. It seems kids could swallow the magnets where they could become lodged in their intestines with one magnet holding firm to another through the intestine walls. If you search on Amazon's website you can find plenty of neodymium magnets for sale, some of which have user reviews containing warnings about serious injuries from two magnets snapping together suddenly with skin in between. Ouch. These sorts of things are unlikely with the amount of rare earth alloy used in the Xume adapters, but some readers may be skeptical about having them anywhere near their cameras. A camera is basically a fancy computer after all, but few of us are still using spinning Microdrive compact flash cards or anything else sensitive to magnets. Apple very successfully uses such magnets to hold power cords onto their laptops, and my Samsung phone can sense the magnetic clasp on a case or docking station. Magnets are everywhere. There's really no cause for alarm that they might harm your camera.
One potentially legitimate concern though is getting iron filings from soil or other sources attracted to the adapters and fouling the threads. Anything with an iron component would be attracted. Doing some further informal testing, only the lens half of the Xume system is magnetic. The front filter half is metallic of course, but not itself magnetic. The two rings are held together solely based on the magnetic alloy used in the lens ring. It would seem prudent to feel around the threads on the lens ring before attaching it, but the filter adapter ring seems no more hazardous than any other step-up ring or similar gizmo most of us already use.
Xume sells the two rings separately or together in various kit combinations. As you might guess, the lens adapter ring with the magnets costs more than the filter ring that doesn't have any magnets. For about fifty bucks you can get a kit with one lens ring and two filter rings. Smaller sizes are less expensive than larger diameter ones.
You also need to consider what size or sizes you'd need for your lenses. Many Nikon professional lenses standardize on 77mm filter threads so this is the only size I own. No reason you can't use these together with step-up rings too but be aware that the more you stack together the more likely you'll run into potential vignetting problems. The two halves of the Xume system together are no thicket than a standard filter, but with your polarizer or neutral density filter atop that you're already up to the thickness of two filters.
Both parts have knurled ridges at two places around the ring to make it easier to get a grip on them but I haven't found any problem no matter where I grab them. There are otherwise no markings of any kind on the rings – no brand name and no model numbers or even an indication as to the thread diameter.
Xume also sells their own lens caps that fit directly on the lens adapters but I personally haven't seen a need for them. You can mount your standard lens cap into one of their filter adapter rings just the same as you can affix a lens cap on the front of a standard filter.
It would have been great to have these things way back in the day when I shot film, but today I use filters far less often. But I guess since the neodymium alloy wasn't even discovered until 1982 there wouldn't have been much chance even if someone had thought to use them this way. Still, for simplifying the use of neutral density filters and polarizers today, they're well worth it.