Evening star., 1951-02-11
Camera Angles

The Mat
Making pictures indoors with
the aid of a synchronized flash
gun is a cinch. This is no exag-
geration. All you have to do is
hitch the flash gun to your cam
era, decide on the shutter speed
and subject distances, refer to an
exposure guide, determine your +.
stop, and you are all ready to
shoot your first flash picture.
That is the story in a nutshell.
We will expand upon 1t and throw
in a few suggestions.
To begin, let's take a look at
the factors which will govern your
exposures. First, as in normal
daylight photography. you will
have to know the speed of the film
that you are using. Without this
knowledge you will be stymied
right because a film with speed
of 100 is going to react to a given
amount of light just twice as much
as a film with a speed of so. You
shouldn't have any trouble on this
score though because the film
speed will be given on the data
sheet that Is packaged with the
film. This same data sheet will
supply you with the photof1ash
exposure guide numbers.
Shutter speed is another factor
that must be considered when
computing flash exposure. This,
of course, will be determined by
you at the time you are getting
ready to take the picture. A shot
of a fast-moving child might call
for a shutter speed of 1I2o0th of
a second while an exposure of
l1/100 second might be ample to
stop motion of another subject.
Light Is Pre- measured in Bulb.
Lighting is figured differently
than when shooting by daylight
or foodlamp. Instead of measur-
ing the light that is being reflected
from the subject, we procure our
light from the flash bulb. This is
pre- measured for us, so to speak,
and each type of bulb emits q
rated amount of light. This being
the case, we have greater control
over flash lighting than with
natural or food lighting. And,
as we shall see, the angle at which
the light is fired at the subject in
relation to the camera position
will also make a difference in the
exposure calculation.
The remaining factors are a.
distance from light source to sub
ject and (2) f. stop. The former
controls the latter, all other fac
tors remaining constant. Now,
all that we have said above re-
garding the various factors con-
trolling the exposure may be in
seeming contradiction to our ini-
tial statement, but actually we
have done no more than recapitu-
late facts that you already know.
with a couple more thrown in for
good measure. You need concen-
trate only on the new elements:
Cd The distance from lamp to
subject, (2) the angle at which
the lamp is placed in relation to
camera position, and CD the
amount of light which the lamp
emits.
We mentioned flash exposure
guide numbers. These numbers
will be the basis for your flash
exposure calculations. They can
be found either on the film data
sheet or on the corrugated con-
tainer of the flash lamp. The
guide numbers found on the lamp
carton are based on the power Of
the lamp with reference to the
speed of various films, and to va
rious shutter speeds. These ref
erenceS to film speeds are too
general to suit my taste. For in
stance, a guide number (the use
of which will be subsequently ex-
plained) refers to films rated at
between 80 and 1875, leaving a
fairly large margin for error.
Calculations More Accurate.
On the other hand, the table
in the film data sheet is based on
the actual rated speed of the film
with reference to specific lamps
and is therefore more accurate.
Pocket calculators are also avail
able, which will enable you to tell
at glance what the lens setting
should be. These are very mex
pensive and we suggest that you
obtain one if you expect to do
much shooting with your fash
gun.
Now for a dry-run and we will
see exactly how all this works out
in practice. Our known factors
will have 10 be the basis for our
computation. Let us assume that
we want to take a flash shot of a
group of people at wedding re-
ception. The chances are that
they will be moving around and
you will have the problem of
stopping" them on your film.
Let us say that you have selected
a film with a. rated speed Of 100.
You decide also that you want to
use an exposure of 1900 of a
second. You further decide to use
a G. E. No. % f1ashlamp for the