In the latest firmware update we've rolled out to the Time Filter, we've added an often requested feature: variable neutral density. Here's how it works: if the system is shuttering (running the Tessive shutter or a 180 degree global shutter) then the system operates at 2.5, 3, or 4 stops. When in this shuttering mode, the camera is set to a 360 degree shutter, so you gain a stop back compared with running at a 180 degree shutter, so these are effectively 1.5, 2, and 3 stops. We always display the effective total stop loss of just the Time Filter on the main display, regardless of what the camera shutter is set to, so you can compute exposure as though it's a neutral density filter.
If you don't want to use the Time Filter to do any shuttering, you can turn shuttering off and just use it as a steady, unchanging variable ND filter. In this mode, it can provide ND from 2 to 7 stops in half-stop increments.
The Time Filter cuts light wavelengths down to 750 nm, which means it cuts the infrared that sometimes causes brownish casts to dark fabric when imaged with a CMOS sensor. Therefore, it is a variable IRND.