Using fill in flash on backlit subjects?

Question

I am using a nikon d40. When I use the fill in flash to illuminate my subject's face, do I have to worry that the flash will cause the rest of the picture to be over-exposed? I am using the p setting so I can pop the flash myself. Should I set the flash output to -.3 if I want just a touch to illuminate the faces on a overcast day? What about a reallly bright, sunny day?

The subject is wearing a hat so face is still in the dark. Also, how does one juggle the exposure compensation with the flash output settings in such a situation? If I use a -.7 exposure compensation, that will take care of the picture as a whole? Does the flash output will only take care of the subject's face?

Thank you!

Answer 1

In general, use minus flash compensation in shade and backlight.  Use more power for bright sunlight.  In P mode, the flash will be adjusted for fill, but if it's a bit too much or not enough, use the flash compensation until you get what you want.

Answer 2

No. The D40 has a balanced fill flash when set to the green program mode. Of course there is a minimum and maximum distance that you need to be in for correct balance. You may want to minus or plus your flash output to get the results you want. The SB 400 is and excellent add on flash that will give you a bit more light than the pop up

Answer 3

You don't have to worry about the rest of the shot.  The flash will be just enough for the subjects face ... you can try different outputs to get just the fill you like ... experimenting is inexpensive, since you are not using film.

Look up the inverse square law on the Internet referring to light and you will understand why you don't have to worry about things behind the subject being over exposed.