When using direct flash you can generally get by quite well by holding
aperture and distance constant. If you once determine that you get a
good exposure at f/5.6 and 10 feet it will take a big change in ambient
light to invalidate that. Just maintain the aperture and the distance
(by using your zoom for framing) and you will have good exposures.
The inverse square law can be pretty harsh at times but increasing
distance mitigates errors of distance. For example, when trying to
maintain a 10 foot distance as above, misjudging the distance by 2 feet
and shooting at 8 feet instead of 10 will result in nearly a 2/3 stop
overexposure. You could decide to shoot from further away. Shooting
from a planned 15 feet and accidentally shooting at 13 feet instead
would only be about a 1/3 stop error. The problem with moving further
away is that your flash begins to more closely approximate a point
source and casts harsh shadows. But bouncing the flash can mitigate
both problems. If you have a good bounce surface overhead it makes for
a very large diffuser and eliminates the harsh shadows. Then the
additional distance traveled to the ceiling and back down again also
helps mitigate the inverse square law by reducing the effect of distance
estimate errors.
If the background is dark you need to drag the shutter to expose the
background with ambient light. Use a long shutter speed to expose the
background about 1 stop less than full exposure and then use the flash
to stop the action and bring the subject up to full brightness. When
shooting events I'm using the studio flashes to fill the background with
light about 1 stop less than full exposure since a dance floor or
banquet hall may have almost no ambient light that's usable. Usually,
the camera can't even see to focus without a focus assist light.
Chuck Norcutt
Jeff Keller wrote:
..
>
> However if you are going to be taking pictures under unique and
> changing conditions for almost every shot, some type of auto flash
> could be very useful.
>
>
> The biggest problem with a single flash mounted near the camera is
> that the light falls off with distance. The background often ends up
> too dark.
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