I have a question about the eye point at a camera. There is no problem that setting an eye point at a camera. But after I change the focal length, the eye cannot point at the camera, it points slightly aside. I heard that I can set the eye point at a invisible prop and put the prop in front of the camera, yes it works but it is hard to keeping the prop in the right place. Can anyone tells me how to do it easier? Thanks!

If you change the focal length of the camera, its scale changes too. Set the scale of the camera back to 100%. (You may have to move it again.) Now the eyes should look into the camera.

i go to try that , thanks Yuri!

Also you could try parenting the prop to the camera, this will move the prop when you move the camera, and might work when you do other things to the camera.