I do not use filters very often, and I only use filters with effects that cannot be replicated in postprocessing. I don’t use ND-grads anymore. However, the effects of a solid ND and a polarizer is difficult to achieve in postprocessing, so I use those filters from time to time. Alas, I need them in my bag. Since I have several lenses with filter-threads ranging from 58-77, having a couple ND-filters and a polarizer for each thread-size would add up in both volume and weight, and be quite expensive. Not very practical, seen in light of how seldom I use them. I used to carry around a conventional filter-system, holder and everything, with an adapter-ring on every lens. It also made up a significant volume in my bag, and to be honest I disliked the process of setting it all up. So I have been looking for a simpler solution for a long time.
A couple of years ago, H&Y filters introduced the Revoring. In short, this is a ring with a variable diameter filter-thread that is easily snapped on lenses with several different filter-sizes. The ring comes as an adapter only or with a CPL + 1.5-10 stops variable ND mounted. Since I rarely use anything but these filters, I opted for the latter choice.
The Revoring is made of three parts. Closest to the lens is of course the adapter-ring. This ring can be rotated, making the filter threads smaller. You then push it against the filter threads of your lens and let it go. The ring is spring-loaded and will snap into place on your filter threads, independent on the size (within some limits, of course). You may have seen videos of this on youtube. Very easy and fast, no screwing, and it sticks in place. The two other parts are two CPL filters. Rotate them both together and you will alter the polarization. Rotate one of them while holding the other in place, and it works as a variable ND-filter. You can combine the effect as desired by first turning them both until you have polarized to your liking, then turn one of them while holding the other in place until you have achieved the ND-effect you want. This may sound complicated, but in practical use, it works like a breeze! You just snap the filter on, polarize, adjust the ND, and you’re done. The two polarizers are equipped with small handles that makes rotating them easy. A printed scale shows how much ND-effect you have. To take the filter off, just turn the adapter ring agains the spring and remove it.
Too good to be true? Well, of course the system has it’s limitations. Variable ND-filters suffer from the dreaded X-effect, or cross polarization. As all other variable ND-filters, this one is made by two polarizers that you turn against each other to block out light. If you push the limits, the darkening will turn up as a black X over your image, and the rest of the image is brighter and may suffer weird color-cast. This effect is most visible with wide-angle lenses. The wider the lens, the earlier the X-effect sets in. With longer tele-lenses it’s not a problem. H&Y have published guidelines for how much ND-effect you can put in on different focal lengths before you see the X-effect. Se table below.
So, what do you do if you use your 16mm lens and want 10-stops light-reduction? Well, H&Y have addressed this by making several different magnetic solid ND-filters that you can attach to the front of the Revoring to add to the ND effect. That way, you don’t have to use the variable ND-filter built into the Revoring for anything but fine-tuning 1-4 stops. In real-world situations, I find that this works excellent. I can use the Revoring alone to reduce light slightly, for e.g. waterfalls, etc, but if I want a strong effect, I snap on a magnetic ND and then add a touch of fine-tuning from the variable ND. H&Y also make a couple of other magnetic snap-on filters for the Revoring (a star- and a three different black mist filters, I suspect other will follow). You can also get a magnetic lens-cap.
The Revoring is made of high-grade aluminum and seems well build. I have lost it on the ground a couple of times, no harm done. Be careful with moisture and dust. If you get it between the different components, I suspect it could be hard to remove. The glass is top notch German Schott and the polarizing effect it achived with film from Nitto, the japanese factory that makes the glass for Hasselblad X-lenses. All glass is coated to avoid finger-prints and water-droplets. Take-home message, no significant color-cast and no reduction in sharpness/definition. As with all filters, you may experience a bit more ghosting and flaring than without filters. The CPL-VND Revoring comes in four different sizes: 37-49mm, 46-62mm, 58-77mm, 67-82mm and 82-95mm.
In use, I find that the Revoring works perfectly for me. The 58-77mm fits an all my Hasselblad xcd and all my adapted glass. It is a high-quality, compact and lightweight solution for the photographer that don’t use filters all the time, but still would like the option of using a polarizer and a solid ND-filter for the odd situation when opportunity presents itself.
I have previously been associated with H&Y filters as an ambassador, but not currently. I have no current financial or other interests. This is only my personal experience and opinion.