### Results of stereoRectify() not as expected

Hi,

I've got a little problem with the results of `stereoRectify()`

when using the ~~cv2 ~~`cv2`

python module. I calculated the matrix `R`

and the vector `T`

using `stereoCalibrate()`

for 2 converging horizontally aligned cameras (rotated inwards by 15 degrees each). `R`

is the rotation matrix that makes the right camera's principal ray parallel to the principal ray of the left camera (when applied in the right camera's coordinate system). It rotates the principal ray by 30 degrees (clockwise if you're looking on top of the two cameras).

What I'd expect the matrices `R1`

and `R2`

(calculated by `stereoRectify()`

) to be, is a rotation by -15 degrees for `R1`

and a rotation 15 degrees for `R2`

to make the principal rays parallel. But it's the other way round. `R1`

is a rotation by 15 degrees and `R2`

is a rotation by -15 degrees around the coordinate system's y-axis.

Why is that? What am I missing? Are these matrices not meant to be applied to the cameras but the (virtual) image planes? Note that the rectification does indeed work as intended and I get correctly rectified images when I pass R1 or R2 to `initUndistortRectifyMap()`

and use `remap()`

after that. I'm just trying to figure out what `R1`

and `R2`

actually mean and the documentation of `stereoRectify`

does not really help.

I appreciate any hints. Thanks a lot.