general rule of thumb is that a light source should be twice as big as
the
subject. I try and try to convince portrait photogs of this.

A 12 foot umbrella to photograph a 6 foot person?


yes, well, not an umbrella but a 'softbox' which can be a flash head or two
behind a curtain, white wall behind, heck just bounce your flash off a side
wall.

Btw, umbrellas are basically a large form of parabolic reflector meant to
force the light towards the subject in a wider field than a spot light, but
in typical use are similar in effect to those parabolic reflectors used with
photofloods. IE: an 18in flood light was typically used about 3 feet away
for a head and shoulders, whereas 36in brollies (typical size when they
first came out) were typically used at about 6 feet away.

A 12 foot wall of light emulates light from an overhang like a porch, a big
window like you find in commercial building lobbies, shade at the penumbra
of a large tree and not quite as soft as twilight.

You get a very soft forgiving light that allows you to get great tone and
detail in the face from the brightest spectrals to the shadow. Most people
tend to loose spectrals, and cause their key light is so contrasty they need
to add more spectrals on the shadow side, (you know the fill light) and even
worse they place it well on the other side from the key light. As a bonus
you get fabulous 'depth of light.'

try it, youll like it, besides why go to all the trouble to do a set up just
like every other photographer in the business. Only a handful of photogs
(that I know of) do north light, either flash or an actual north light
window, the light used by portrait artists since the invention of the
portrait with paints, everybody else acts like it is required to use
lighting that is contrasty enough that it needs help with a fill. From the
prom shooter to the kiddie pix guy, the passport shooter (well since
polaroid took over the business its been the cyclops flash right over the
lens) the school picture shooters.

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