Re: I have about 10000 images of different persons with dimension of 640*480. I wan to crop face from these images to dimension of 200*280. The location of face varies in differnt pics. So, please let me know step by step how can I perform this using the

The aspect ratio should be set to 200x280, or equivalently 5x7.

I don't think it is possible to do the cropping automatically in Lightroom, you'd have to do this image by image to crop the faces correctly.