Anamorphic Calibration

introduction while the general process of calibrating anamorphic lenses is similar to the typical spherical lens workflow, there are a number of differences that are explained here it is strongly recommended that the user is comfortable with the process of lens calibration prior to calibrating an anamorphic lens this page details the steps specific to anamorphic lens calibration and assumes a knowledge of camera and lens parameters camera when determining the active sensor area inside the main camera details tab it is important to multiply the width value by the anamorphic multiplication factor that is being used de squeezed monitor output ensure that the monitor output signal that is being fed into the ncam server has been de squeezed for example, an arri alexa lf in 4 5k open gate mode has an active sensor area of 36 70mm x 25 54mm if working with an anamorphic multiplication factor of 2 , the values that should be entered are 73 4mm x 25 54mm the magenta lines should still be aligned to the monitor out picture as normal lens parameters of the lens should be entered as normal when selecting a lens distortion model, the " cinelens anamorphic degree2 experimental " option should be used the squeeze factor and "de squeeze video feed" options can be left unchanged chart the 3cm square checkerboard chart should be used for all anamorphic lens calibration it should be positioned perpendicular to the camera so that the chart is as flat as possible and fills the frame of the lens the vignette reduction docid 5zvxhgt30n1hv kpqtu0 tool and additional lighting should be used to try and help the detection of the chart profiler settings once the chart is positioned in front of the camera, the distance from the sensor to the chart should be measured and entered into the relevant field of the lens profile tab additionally, the h=v focal checkbox should be unchecked this will be done automatically by the selection of the anamorphic lens distortion model if it is still checked then confirm that the correct lens distortion model was set in the main camera details tab the 3cm square checkerboard option should be selected from the " chart " dropdown press start for the detection of the chart to begin an overlay will be drawn over the pattern if it is successfully detected a green dot is also displayed and this should be as close to the centre of frame as possible process once everything is positioned correctly, take a number of images of the chart from this single position and calibrate, this will create our first "golden point" following this it is recommended to exit the lens calibration and conduct a witness to main to allow the placing of the ncam cube in the environment to then subsequently check the quality of this initial point of the calibration this process is described in the lens profiling docid\ clbbkwk3oakpdtonejqts section it is likely some manual adjustment of the calibration values will be required initially check that the h and v image centres are approximately 0 5 if the values presented from the calibration differ wildly, manually enter values of 0 5 for each this can be done by ctrl+lmb the relevant point in the graph tab and then manually altering the fields in the parameters tab continue the process of creating additional points using the chart and checking the quality of these points against the "golden point" moving the chart the position of the chart can be moved further or closer to the camera for each calibration point, simply remember to re measure and enter the new distance to the chart in the profile tab before proceeding