Fill Flash and Window Reflections

I was shooting a portrait indoors about 10 feet in front of a bright window with a 10D and 550EX. On manual exposure, I metered the background. Using that meter reading I then selected various flashes from -1 ½ EV to -1/2EV flash. The fill flash was hardly noticeable at any setting.

I then read the following in April, 2005, Popular Photography, page 44

When shooting a portrait indoors with a window in the background, make sure you angle the shot so the flash doesn’t reflect back toward the camera and reduce the flash exposure

I was shooting head-on and did notice flash reflection on the window. Has anyone had this experience or can explain this phenomenon?

Angle of incidence = angle of reflection. If you stand to the left of a mirror can you see yourself in it? Spend an hour shooting pool & it will all become clear to you.

I suspect that what may be happening are two things if you are facing the window:
1. The bight sunlight from the window is forcing you to use an aperture that is too small to get any effective flash distance. The shutter speeed is limited to the sync speed of the camera. Remember, the maximum flash distance = Guide Number of the flash/ f stop at ISO 100.
2. The preflash reflecting off the window glass is shutting down your flash.
I suggest not facing the window but use it as a side light. If you can't do that then you need to bump up the FEC or use a more powerful flash. You could try raising the ISO, but that will exacerbate the small aperture problem.
Scott

I think what Scott is saying is that often it gets better results to have your subject turned 90 degrees, so that the camera is shooting and flashing at a right angle to the light through the window.

What is that going to do?

1. Your camera metering will not see the full brightness of the window light. It will likely see some of it bouncing off the sunny side of the subject.
2. If and when the camera flashes, the light is not going to hit the glass squarely and bounce right back at the camera.

Simple.

---Bob Gross---