Camera Settings

When setting up the camera for lens calibration, it is important to know a few things about the technical specifications of the camera itself (like sensor width in mm) and know to change settings in it when necessary.  Also, you should be familiar with lens controllers and how to properly set it up.

• Mount the camera on a tripod or wheels/dolly.  The camera does not need to be at the same height as the center of the marker board.   The lens calibration room should accommodate for the size of the lens calibration target, its oscillation and at least a range of camera distances from the board of up to 8 meters, or about 26 feet.
• Set your camera to record at your preferred frame rate, but keep in mind that, for the lens calibration process, you can only be in Progressive (RED cameras) or PsF modes.  60i or interlaced modes create a “comb artifact” on the video that causes problem for lens calibration.
• Make sure that the camera is powered and is able to run for a few hours, depending on the number of lenses to calibration.
• Turn off any and all image adjustments that control sharpness and edge enhancement.
• Make sure there is no image mirroring or image flipping enabled.
• Make sure that focus assist and any menus are off the screen.  RED cameras, for instance, change the actual size of the image on its live output when there is a menu up on the EVF.
• Set camera EI/ISO to its native rating.
• Turn off all gain adjustments.  Add more light to your marker board if necessary.
• Stop down the lens to an F-Stop that diminishes drastic depth of field in your image.  Between 5.6 to 8 is a good setting for super-35 size sensors. Again, add more light to your marker board if necessary.  Use the camera’s histogram to determine proper exposure.  During the calibration process, you may open up the lens to its brightest, focus on the board and then stop back down for the actual process.
• Mount lens to be calibrated and connect/gear up the lens controller to the lens.
• Plug the Lens Controller to “Lens” on the front of the Airtrack and make sure the Aitrack is plugged in and receiving power

Required Gear

For being able to map the limits and values of a lens’ focus and zoom ring, Previzion requires an encoded lens controller like a Preston FI+Z II/3, CMotion, LDS Lens, etc.  It is important that the lens controller is encoded, because otherwise, there is no direct feedback from the lens’ positions.

For this, you will need:

• Production camera
• Lenses being used
• Appropriate lens controller
• Lightcraft Aitrack
• Lightcraft Data Cable Tether
• Appropriate lens cable (goes into Aitrack via 4-pin Lemo)