112 THREE-DIMENSIONAL PHOTOGRAPHYthan the lens and about twice as far from the subject as the first
one.
DAYLIGHT FLASH.-TO most amateurs flash means night, but
there are many times when the value of flash in full daylight far
outweighs its value as a night illuminant.
First of all let us catalog some of the ways in which flash may
be used in daylight.
Shooting against the sun; shooting where the light is spotty;
where there is a big differential between foreground and back-
ground illumination; exposures on the beach and other locations
of intense light; making shots in mist or fog; making shots in the
rain; stopping rapidly moving objects; groups under overhead
shade; modeling groups in cast shadow; adding intensity for
morning and evening shots; adding accents to otherwise flat illu-
mination... and more may be added.
In short, the daylight flash adds to the picture in intense sun,
in bright sun, in hazy light, under overcast skies, in very low light
and in mist, fog or haze. Which may all be summed up by saying
that flash can add to the picture quality in any kind of daylight. It
would be going a bit far to say that any outdoor picture can be
improved by flash, but for any type of subject in which the center
of interest is confined to the foreground, the flash will add to the
picture in about 75 percent to 80 percent of all exposures.
At first it seems foolish to make use of such an insignificant
light source as a flash when we have full sunlight, but after all
let us consider that even with a midget 25 bulb ten feet from the
subject the exposure is 1/50 at fg. This is just about the exposure
for intense sunlight, assuming an index of 8 for both. Thus we
may consider that at about ten feet, more or less, the intensity of
the flash and of the sun are about equal.
But note this difference, at 20 feet the sunlight has not altered,
but the flash is 1/4 sun intensity. While the sunlight remains un-
changed, the flash dies at this rate: 30 feet= i/g; 50 feet= 1/25
and so on. For all practical purposes, and under the conditions
stated, the flash effect will die out at not more than 30 feet. If
the sunlight drops to half normal, it will balance at between 14
and 15 feet and so on. So, in the flash we do have a light source
which is comparable in intensity to sunlight, provided the sub-
ject is located at a relatively close distance.