FLASH IN STEREO 111more costly than the clear type and have a decidedly lower output.
For example the Sylvania SF (F) has a peak lumen output of
800,000, the Press 25 (M) has 1,250,000 while the 25B (M-blue)
has only 500,000; this is actually less than the output of the F
type of clear bulb.
It is economical to dye your own bulbs. This may be done by
dipping them into a solution such as Jen-Dip provided you dye
two or three dozen bulbs at once. It is not economical otherwise
as the dye is highly volatile and often when you return to dye
another small lot you find the bottle empty!
Dipping is also advantageous in that the dye strength depends
upon the time of immersion and by care you may make up your
own correction to give just the effect you want.
Another method is to use a filter over the reflector. This is least
costly, and it works all right. The filter used is ordinarily incor-
porated with a protective shield which prevents particles from
flying if a bulb should burst, as occasionally does happen. We
have found the combination entirely satisfactory. However it must
be remembered that the low efficiency of the blue bulb is due to
the absorption of the more plentiful red component, and any
filter will have a similar effect, so whether you use blue bulbs,
dipped bulbs or filter, use the guide number for the blue bulb
which corresponds in size to the bulb you use.
MULTIPLE FLAsH.-The usual flashgun will ordinarily handle
two bulbs, in extension work, without difficulty. If more than two
bulbs are to be ignited at once, it is advisable to use some ignition
system designed for this heavier load to insure prompt and sure
fire. For elaborate layouts a special power pack is used, but for
intermediate use, such as from three to six or eight bulbs, the
simplest solution is the use of a gun which incorporates a con-
denser. This stores up a charge and when released hits the bulbs
with a heavy “kick.”
As a rule it is advisable, when using extension flash, to have no
bulb in the main gun, as this would tend toward the flattening
effect typical of any gun attached to the camera. It is necessary to
have a shorting plug in the main gun when bulb filaments are in
series. Usually one is above the camera, at one side and nearer
the subject than the lens; the other is at the opposite side, lower