Im having trouble understanding the time when one should use fill flash. Is there a exposure setting when you should use it or what? This is one thing that really confuses me as if its so hard to do that anyway. Thank you in advance for any advice.
I think of it as "filling in" the shadows. If there is a situation where something I want to see well is in a shadow, (like when a person is backlit, leaving their face in the shadow) I use the flash to brighten it. I'm sure there are many other times or uses but this is about as basic of an example as I could come up with. Edit: thought of another explanation... more about when to use it. I think one of the books/websites (can't remember) I read said something along the lines of compressing the dynamic (tonal?) range of the photo, meaning if there is too much difference between the bright area and dark area of your shot to get an acceptable exposure of both, you can use fill flash to brighten the shadows enough to acheive an acceptable image.
Yep, and you meter for the background so the bright background doesn't blow out from being way overexposed. When you use flash the aperture controls the exposure of your subject, the shutter speed controls the exposure of the background, and the flash of light stops motion because at full power the duration of the flash of light is short, about 1/1000 of a second.
Fill light (including flash) is used to control shadow exposure. When you have a light source that is not on the same angle as the camera, that light will likely give you both lit areas and shadow areas on a subject. For example, if the sun is above a person, it will likely cause shadows under their eyes, nose, chin etc. Fill light is typically directed to the subject from an angle that is closer to the camera, or maybe on the opposite side from the main light...so it is likely to light up those shadow areas caused by the main light. For example, an on-camera flash will light up the shadows caused by the sun. The brighter the fill light, the brighter those shadows will be. So by controlling the amount of fill light, you can control the ratio of bright areas to the shadow areas on your subject.
