My last post covered the law of light that says the angle of incidence equals the angle of reflectance. In other more understandable words it means that light bounces off of a subject at the same angle as the light falling on it.

Another use for this rule is photographing something in a mirror. Here’s the simple rule: show the mirror in the photograph what you want it to show the camera. Consider the photograph below. A golden framed mirror resting on a lady’s vanity reflects a brown frame right? Look a bit closer.

Do you see "mirror, mirror in the golden frame" or "mirror, mirror on the wall?"
Do you see “mirror, mirror in the golden frame” or “mirror, mirror on the wall?”

The frame is just an empty frame. All it frames is the whole mirrored wall behind it. That’s why the back of the frame on the left appears to be outside of the frame in front of it. It makes the room look a lot larger by reflecting the plantation shutters covering the windows.

With Carrie sitting in her chair sipping an espresso, the scene becomes more visually lucid. Then I asked Carrie to look in the mirror then shift her position until she could see my camera centered in it. She turned back to the camera. Click. Carrie and her profile both show.

Moving Carrie's head to the right reveals her face in the mirror.
Carrie moves her head towards the window to show all of her face.

While setting up how does a photographer know where to put the subject to be reflected in the mirror?

Simple. Put the camera on a tripod and frame the scene with the mirror. Now walk around the mirror until you see the camera. Where you stand is where the subject has to be to show in the mirror. The place where the camera shows is where what you want in the mirror has to be.

The angle from the camera to the mirror is the angle of incidence. The view of the camera in the mirror is the angle of reflectance. The angle of incidence rule is more than lighting. It’s for composition too!