Sometimes you want a subject to “pop” out of the background. A telephoto lens combined with a wide aperture is one way to extract your subject from the background. Use flash to heighten this effect.
Why use over exposed flash Flash 
If you are outdoors and want to darken or capture the detail of a bright sky behind your subject then over expose with your flash. This is a great way to get rich blue skies in flash photos, or to play-down a distracting background by darkening it.
Step One:
- Set the ISO on the flash gun to the ISO film you are using
Step Two:
- Set your shutter speed to 1/125th of a second
- (check your camera sync speed is compatable)
- Take spot light meter reading of the brightest part of the sky
- Use your camera or a handheld meter to determine your aperture setting
Step Three
- In manual mode on your camera start by setting your apeture to 2 stops less than the reading you got for the sky
- Take the picture, In the resulting photo, the flash-lit nearby subject will be properly exposed, while the ambient-lit background and sky will be underexposed by two stops.
- Play about with different settings till you find an exposure compensation you like, typically between 1 and 2 stops gives nice effects.
| Reading from sky | Shutter speed | Aperture setting |
|---|---|---|
f8 |
1/125th |
f16 |
f11 |
1/125th |
f22 |
f16 |
1/125th |
f32 |
f22 |
1/125th |
f45 |
Now, treat the ambient light exposure as a creative decision. The more you underexpose the background, the more prominent your flash illuminated subject will become. You can even purposefully underexpose the background so all background detail is “lost” in a sea of blackness. Careful use of this effect can create very dramatic photos. Alternatively, overexposing the background can produce exciting photos with backlit subjects.
Another way
- If your camera offers flash exposure compensation, just dial-in +2.
- If it doesn’t, dial-in –2 stop of exposure compensation for the ambient light, using the camera’s normal exposure-compensation feature.
Note : Dont change your shutter speed, that way with practice you will learn what settings to use.
Tip:If your lens will not go two stops less, CHANGE your ISO.