degrees of freedom u2014 focal length and zoom x y and z and pitch roll and yaw focal length and yaw or vergence in this instance are the most important to us the alignment of x y and z manually may be good enough to bring the two detectors onto almost identical points 0 0 on their local x y planes differing only by their global offsets a and u2212 a on the z axis in fig4 and fig5 we note that in all the transforms below we use the local coordinates of the detectors rather than the global coordinates discussed later for image mapping for all transformations that is that when our alignments are carried out to a sufficient degree point x i y i of detector 31 will correspond almost exactly to point x i y i of detector 32 the adjustments then apply to the focal length and zoom pitch roll and yaw it may be convenient here to place the two images of a scene side by side on a display containing cross hairs or fiducial marks the roll can be adjusted manually by aligning a left and a right vertical image say of a tree against corresponding vertical lines on the screen the vertical position or pitch can now be manually set against some common horizontal projection u2014 such as a branch on the tree these two actions will also define the yaw or vergence of the two cameras upon the tree the final manual adjustment applies to focal length and zoom by adjusting two or more corresponding widely separated features the two images near or on the primary plane 25 may be made to appear the same size to the eye with proper alignment tools this process can typically be done in a few.