Centos 7 x64
GTX 970 + GTX 560 Ti
Broken: 2.76 and master
Short description of error
Cycles recently got camera zoom motion blur. While it works in regular perspective cameras, it does not work in ortho cameras. I've attached a file to demonstrate.
Exact steps for others to reproduce the error
Open the blend. Select camera and ensure type is perspective (regular). Render frames 3 and 14 with perspective camera. They render with blur properly. Switch camera to ortho type and render frame 3. Ortho scale is animated, but there is no blur. Motion blur only occurs when the camera is being translated along the view plane, but not with zoom alone.