Mateo: no, you only need one photo, because of the way any point on a mirrored ball reflects the whole of its surroundings. In principal though you get some distortion around the edge. If you look at my picture 3 above you'll see this distortion left of centre of the sphere. Compare it to the photo 1 and you will see that you can actually see quite a lot of detail in the render to the left of the window which is around the edge of the ball in the original photo. If you want to create a faultless panorama, and get rid of the photographer, then you do take two photos, but at 90 degrees. HDRShop can put these two together. If you're interested I could send you the photos so you can see how it works.