Motorised variable ND filter for professional film productions
The novel Cinefade system synchronises the external iris motor of a professional camera system with a light transmission filter to vary depth-of-field in film.
The same light transmission filter can also be used individually as a motorised variable ND filter that is remotely controlled by a cmotion lens control system to allow for precise and fast exposure changes when the camera is inaccessible or when the creative brief calls for an exact T-stop to maintain a consistent depth-of-field.
There are surprisingly few options available for professional filmmakers who want to use a variable ND filter on professional digital or analogue film camera systems, such as an ARRI Alexa, RED or Panavision camera.
The Cinefade variable ND filter can be used on any camera and cine-lens. It consists of two polarising filters which sit inside a matte box. One of the 4x5 filters remains static while the other is held inside a geared FilterTray. An ARRI CLM4, CLM5 or cmotion cforce motor attaches directly to the handle of the FilterTray without the need for any additional mounting equipment.
Mechanical end stops inside the FilterTray allow the system to easily and quickly calibrate itself at the push of a button, similar to how a lens is calibrated. The filter will therefore not spin freely and rotate through 360 degrees but is limited to a 90 degree rotation and is set to the positions between minimum and maximum light transmission.
The variable ND filter is able to attenuate up to 5 stops of light with an initial light loss of 1.5 stops at full transmission without any colour cast.
VARIABLE ND FILTER FOR SHOOTING IN CHANGING AND UNPREDICTABLE LIGHTING ENVIRONMENTS
There is no need to waste time by constantly changing between full ND filters when you can quickly and easily control your ND value with a variable ND filter.
AC Rafa Miralles is often asked to change between ND filters depending on ever changing lighting situations. It was a real time-saver when he was able to benefit from a variable ND filter that allowed him and DP Harry Patramanis to dial in the required level of ND on set at a fraction of the time it would take to switch out full ND filters.
Shooting a commercial for pharmaceutical brand 'Linzess' in Barcelona, DP Harry Patramanis wanted to capture an unscheduled plane fly-by at sunset with unpredictable cloud coverage.
He used the Cinefade variable ND filter to keep a well exposed image, making constant adjustments as the sun came out from and then disappeared behind the clouds.
VARIABLE ND FILTER TO KEEP A CONSTANT STOP
Depth-of-field is an important creative aspect for cinematographers and can define the look of a project. The current trend towards using large format cameras, such as the Panavision DXL2 and Arri Alexa 65 means DPs are embracing a very shallow depth-of-field look and are often shooting with a wide open aperture.
In order to keep a consistent look throughout a project, DPs want to shoot at the same T-stop under any lighting environment, making ND filters an integral part of any kit list.
A variable ND filter negates the need for a full set of ND filters and allows for small exposure adjustments without changing the T-stop and affecting depth-of-field. Full-stop ND filters are not able to provide that same level of control.
On the set of The Commuter (2018) DIT Tom Gough got excited at the possibilities that a variable ND filter could provide.
DP Dimitri Karakatsanis used the Cinefade variable ND filter on a commercial for Walmart, which allowed him and AC Jesse Cain to work faster and make more precise exposure adjustments to maintain their stop.
VARIABLE ND FILTER FOR CREATIVE INTERIOR TO EXTERIOR SHOT - NO MORE IRIS PULLS!
When transitioning from dark to bright lighting conditions, most filmmakers employ an iris pull during the transition from one lighting extreme to the other to maintain a good exposure. This drastically changes depth-of-field and has always been a drawback that DPs have had to accept.
The Cinefade variable ND filter is remotely controlled, so even if the camera is mounted on a Steadicam, the exposure can be adjusted to maintain a well exposed image during the transition from a dark interior to a bright exterior lighting environment with a consistent stop, allowing for a shallow depth-of-field inside as well as outside and maintaining the look of the project.
The variable ND filter is remotely controlled by the Camera Assistant from the cmotion hand unit that also controls focus and iris and is easy and fast to set up and operate. The AC sets marks for both positions of the variable ND filter and manually moves the slider (or knob) between them during the transition, similar to setting marks for and executing a focus pull.
In the following video, DP Eve M. Cohen shoots a very basic test, showing how a transition shot with a consistent shallow depth-of-field may look like.
VARIABLE ND FILTER ON RUSSIAN ARM, CRANE OR HELICOPTER
Cine-lenses have geared aperture and focus rings allowing motors to be attached to them. Wireless lens control systems control their position so that the AC does not have to physically stand next to the lens. This is especially useful when the camera is mounted on a Steadicam or when it is inaccessible and hard to reach, such as on a Russian Arm, crane or helicopter etc.
The Cinefade variable ND filter also has a geared ring so that a motor can remotely control the filter’s rotation angle using a lens control system. The Arri CLM4, CLM5 or cmotion cforce motors attach directly onto the FilterTray with a 15mm rod and are quickly calibrated enabling the DP and AC to control the exact value of ND required from a distance.
The filters fit into most matte boxes, including the Arri LMB5/25, 4x5 and MB18 matte boxes and take up two stages, one for the static polariser and one for the geared FilterTray.