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Ws per flash tube MW3-1 MW3Q MW9H MW9Q
100Ws 1/1500 1/1500 1/3000 1/3000
200Ws 1/1200 1/1200 1/2200 1/2200
400Ws 1/750 1/750 1/1400 1/1400
600Ws - 1/580 1/1000 1/1000
800Ws - 1/450 1/700 1/700
1200Ws - 1/330 1/500 1/500
1600Ws - - - 1/400
FLASH DURATION
Flash duration of a Speedotron Brown Line system will vary with the type of flash tube,
the amount of power outputted and the number of light units connected to the power
supply. For example, a D402 system with two M90 light units and two MW3R light units
will have four MW3-1 flash tubes and a 400Ws power supply. When set to full power
each flash tube will output 100 Ws with a flash duration of 1/1500 second.
Flash Duration in fractions of a second
Ws per flash tube M90 M90 w/flood adapter M11 w/7" reflector M11 w/11" reflector M11 w/16" reflector M11 w/20" reflector MW3R MW3U w/o umbrella
100Ws 123 80 68 135 105 113 95 95
200Ws 175 115 95 190 150 160 135 135
400Ws 245 160 135 270 210 225 190 190
800Ws 320* 220* 190 380 295 320 255* 255*
1200Ws 385* 265* 230 455 355 380 305* 305*
1600Ws - - 270* 540* 420* 450 - -
GUIDE NUMBERS
Guide numbers provide a starting point in calculating the proper exposure for pictures
taken with flash. A guide number is a constant numerical value (for a given film
speed/ISO) determined by multiplying the light source-to-subject distance by the f-stop
in use on the lens. Consequently, dividing a given (known) guide number by the light
source-to-subject distance will yeld the proper f-stop. For example, if the given guide
number is 110 and the light source to subject distance is 10 feet, the f-stop required for
proper exposure is f/11.
The formula is as follows:
guide number = G G = D x F
light source-to-subject distance = D D = G/F
f-stop = F F = G/D
Important note: Guide number values provide a general starting point for exposure
determination and vary depending on a myriad of factors such as power supply differ-
ences, surrounding area reflectance, flash tube differences, etc. In some instances such
as extreme close-up and macro applications guide numbers will not provide accurate
exposure information. All guide numbers are approximations and we recommend that
test shots be produced to insure exposure accuracy.
The guide numbers bellow are based on exposure from one light only, on axis with an
exposure index of ISO 100 in feet. The information supplied in the chart bellow is most
accurate for use in small, light colored rooms. For large or dark colored rooms it may be
necessary to open the lens 1/2 f-stop. For rooms which are both large and dark colored
it may be necessary to open up as much as one full f-stop.
Light will continue to be produced for about five times the flash duration but will add
little to the exposure. This will not affect action stopping abilities for most normal
contrast subjects.
Guide Numbers at ISO 100/feet
*use quartz flash tube only
Flash duration is measured from 1/2 peak light output to 1/2 light peak output as
illustrated below:
Peak
1/2
0
flash duration