Pop up your flash and put your camera in “P“rogram mode. The camera will automatically use the flash as a fill flash.
A little more control if you over 10 feet away
You will need a dedicated flash for your camera model
After mounting the dedicated flash on your camera via the hot shoe, you need to set the flash controls to “TTL” mode. This may be illustrated by the LCD showing “E-TTL”, P-TTL” or other “brand” specific code.
with this type setup, you may have a few more camera modes you can use. Such as “A“peture mode, or “M“anual mode.
Using Fill Flash with the camera on “M“anual and flash on “A“uto (not TTL).
This will allow a bit more control of the background brightness if you need to adjust it without adjusting the flash output.
Set your shutter speed at the “Flash Sync” speed. Usually 1/160 to 1/250 of a second. (see your camera manual for the “Flash Sync” speed)
Set your flash and lens aperture for the proper f/stop for the distance of your subject.
Focus and shoot.
This will achieve a proper exposure for the your subject for the photo. But, the background may turn out too dark.
For Digital Cameras OR Shooting Slide Film
If the Background is darker than you want, you can add exposure by “Dragging the Shutter”.
using the method for exposure above….Use a slower shutter speed than the highest flash sync speed for your camera.
So, if, your exposure was 1/160 at f/5.6,……USE 1/50 shutter speed instead. Keeping the f/stop the same for the flash you set for your subject distance. This will brighten the background by about 3 stops. Remember, it is the f/stop that determines the proper flash exposure. The shutter speed will determine how the areas around the flash are lit with the subject being properly exposed.
If the background is too light, use the next faster shutter speed, and check it out with the preview.