Last Modified: December 3, 2014
Lens Calibration Hardware
Lightcraft’s lens calibration system ships with:
- 14-foot lens calibration marker board that breaks up into 3 parts,
- calibration motor and mount,
- 12-inch offset rod,
- 220V-to-110V transformer (when requested),
- European (“Shuko”) to American (“Edison”) power adapter,
- foot switch,
- Allen Wrench,
- (2x) T-push pins,
- travel case for boards,
- Pelican/Storm Case for motor, and
- its own turtle base c-stand
For taking into account wider lenses and various focus distances, the lens calibration system uses a 14-foot wide marker board. The patterns on the board is a known digital pattern that, during calibration, Previzion sees through the lens to determine the various parameters of the lens.
We include a c-stand with the system because often times, c-stands are property of other departments. The lens calibration c-stand becomes the VFX department’s very own c-stand. We also remove the gobo arm from the stand so it can only be used as part of the lens calibration system. The c-stand we use has a turtle base that neatly breaks up and collapses into compact parts.
Shipping and Padding Parts
Because we rely on the flatness and integrity of the pattern of the lens calibration board, it is important to pad and protect the marker boards. The marker boards ship from Lightcraft with a 1/2″ medium density foam.
Just like shipping artwork, we recommend packing the boards separated by foam in between. Use the diagram inside the lid of the case, or download the full PDF from the General Downloads on the Dashboard.
The motor, foot switch and c-stand are shipped in their own case as to avoid damage to the marker boards.
The calibration motor is the only component in Previzion that cannot be customized to 220V. The motor can only work in 110V and for any European customers or customers that specify 220 voltage, we include a 220-to-110-Volt power transformer.
Plugging the motor to 220v will damage the motor.
Marker Board Assembly
As mentioned above, the lens calibration marker board is made up of three parts: center, left wing and right wing. The board does not have an up or down per se, but it helps to define one as left and the other as right.
To put the board together:
- Mount the motor onto the post of the c-stand using the two machined slots and a hex key.
- Place the center board onto the motor mount and fix it using the two t-pushpins.The longer pushpin goes onto the top and the shorter one clicks on the bottom.
- Place the 12-inch offset rod, but down attach it onto the motor yet. You will need to tighten it 8 inches from the center of the board. Don’t screw its other end yet as it may damage the motor.
At that distance, the board will oscillate just shy of 90 degrees.The offset rod has a single rail nut that slides into the top of the extruded aluminum frame.
- With the assistance of another person, attach the side wings. Just like the offset rod, the wings have rail nuts that slide into the extruded aluminum frame.
These are triple rail nuts and slide into the back of the frame assembly.
Please note the sides on the board by looking at the from of the board. There are double hairlines and single hairlines to assist with alignment and determining which wing goes to which side.
- Plug the foot switch in between the motor and a power outlet. Make sure the foot switch is on the off position. The foot switch with serve as a on/off switch for the whole assembly.
- Finally, screw in and tighten the offset rod to the motor shaft.
- Turn on the whole assembly and verify that the board’s oscillation does not hit anything.
The boards may differ in width by up to 1/8″ and the points where the boards touch may not be perfectly straight as these boards are assembled by hand and adjusted to be as optically square as possible.
Board to Camera Orientation
The horizontal board has a nearly 90 degree swing angle. This should be set up so that the calibration target is at about a 90 degree angle to the camera lens axis at one extreme, and nearly in line with the camera lens axis at the other extreme.
This provides the maximum angular variation to the lens calibration system, so that Previzion can accurately calculate the true focal length and entry pupil of the lens.