Specialist filter manufacturer STC Optical Ltd has expanded its range of Clip filters to include a ND64 with infrared-cut properties. The new filter, which clips directly in front of the camera’s sensor instead of over the front of the lens, provides 6 stops of light reduction while maintaining accurate colors by preventing infrared light from passing freely during the exposure.

The benefit of using filters over the sensor is that the same filter can be used whichever lens is fitted, so users don’t have to buy a separate size for each lens diameter, or a different adapter ring. These kinds of filters are especially useful when used with ultra-wide lenses as they present no danger of vignetting and they fit behind lenses that can't accept conventional front-element screw-in filters.

With wide, as well as normal, lenses having the filter behind the lens avoids the problems of flare that adding glass in front of the lens can create. It also side-steps the problem of  reflections on the back-side of the filter that can be a danger during long exposures when using filter holders that don’t hold the filter flat against the front of the lens.

Using this sort of ND filter will potentially be of benefit not only for creating long-exposure still images but also for video work. And of course with the filter remaining in place in the camera, changing lenses will take less time as there's no need to screw off and reattached the filter.

Since the filter prevents DSLR mirrors returning to their normal position, it must be attached in live view mode. STC claims that it is perfectly safe to leave the filter in place even with the camera powered off, since the filter is designed to support the mirror, and prevent it from dropping.

A full list of compatible Nikon, Canon and Sony full frame and Canon APS-C  bodies is available on the STC Optical website. The filters cost $90.