My mistake. Anyway, heres the first pic where I dont zoom. You can see a green curve lines on image plane accurately.

https://s221.photobucket.com/albums/d...rrent=pic1.jpg

And heres where i zoom in, all a sudden the curve move away from image plane.

https://s221.photobucket.com/albums/d...rrent=pic2.jpg

so what us a problem here?