How to set up reference images?

Okay, so I want to create a replica of a helmet from some images on the internet. These images are not straight on and I have no idea what the specs of the camera are. I have tried using the addon BAM with no success. Is there any way to get these images setup so that I can use them as references?


I had a similar problem the other day, wanting to use reference images with wireframe but not in standard ortho views. The solution is to set the images on empties, and then adjust the scale and rotation of the empties to suit.

Instructions here.