Shooting into a mirror - the real focal point?
 

Okay. Let's say that you are 5 feet from a mirror shooting into it. Your subject whose reflection your shooting is 7 feet away from the mirror. What distance is the camera focusing on, the mirror's surface at 5 feet or the subject's image at 7 feet?

The subjects distance at 7 feet is what the camera focuses on.

Mind Bender
 

So, if you're standing behind the subject, it's possible to rack from the back of a person's head to their face in the reflection in the mirror. Also if you are 5 feet from the mirror and if it's focusing on the reflected subject 7 feet from the mirror, then it is truly focusing at 12 feet, right?

Yes, the total distance is the sum of the camera to mirror and mirror to subject.

Right. To the camera, there's no difference between a mirror and a window. You'll be focusing on a point 12 feet away.

"To the camera, there's no difference between a mirror and a window."
Neither to your eye... You'll be looking 12 feet away.

Good point. :)

How is that if the image is in fact on the mirror surface at 5 feet away? It seems as though that the only thing the camera or your eyes would see is that the image is smaller or larger in scale, depending on the distance from the mirror, in the frame or field of vision respectively.

I believe you're thinking of the mirror as if it is "capturing" the light from the subject and then projecting that image to you, in which case your eye and the camera would be focusing on the mirror itself. That is not the case. An image from a mirror is different than an image being projected onto a screen. Your eye and the camera are actually seeing the original light being emitted by the subject which has been relayed by the mirror. The light has actually traveled the distance from the subject to the mirror and then the mirror to you.

It's the difference between projection and reflection.

If this helps, a mirror shot in a feature is measured by the camera assistant by pulling their tape measure to the surface of the mirror, holding it there and having the second assistant continue to pull the tape to the subject, like a bank shot in pool.

I am aware that this is the case from actually doing it but didn't exactly know why. Now I do. Thanks for all the info.