Direct Flash versus bounce flash
> So what I was wondering is what does the bounce/swivel
> do for the average photographer
It gives much better results when you can use bounce flash.
Direct flash causes 2 or 3 problems:
- a large difference between the amount of light in the first plane
and the background. This is a consequence of the laws of physics
(inverse square law) and there is not much one can do about it.
If the foreground is one meter away from the flash and the background
is two meters away, the background will receive only 1/4 of the light,
that is, -2 stops.
- harsh shadows. This is more noticeable when the source of light is
small, so it can be improved by light boxes and similars (light boxes
are a good idea but not very practical).
- red-eye. The solution for that is to move the flash away from the
axle of the lens (a normal flash at medium or small distances already
solves this in most cases). A problem with that solution is that the
shadows get more noticeable,
If you can bounce (that means, if there is a ceiling or wall appropriate,
(white if you are doing colour, some light colour in the case of B&W)),
you can solve all these problems:
These 2 photos are meant to show the difference:
- the inverse square law applies only when the light comes from a
point source (or something small enough to be considered a point
source). If the light is being bounced in a big wall this no longer
applies. Light coming from an infinite plane would not decrease with
distance. Reflecting light from the ceiling is more similar to that
case than to a point source.
- shadows mostly disappear for the same reason. BUT, light from the
ceiling can create shadows under the eyebrowns. This is the reason why
flashs sometimes have a secondary light always pointed to the front
and why accessories like the Luminoquests have ways to reflect 20%
light to the front and 80% to the ceiling.
- red-eye disappears since there is (almost) no light being sent
parallel to the axle of the lens.
The top one was bounced, the bottom one was direct. See the difference
in the light level of the background.