When flash tubes were made of Pyrex glass, it became obvious when a flash tube needed replacement. Miss-firing of the tube after 10-15 shots would be the warning signal that the tube was getting old and ready to be replaced.

Today we are facing a much different situation as most of professional flash tube manufacturers are using Quartz glass and they operate for many years without a miss-firing problem. But other characteristics of these Quartz tubes change over its life span and cause problems that go undetected for years. Most manufacturers warranty the operating life of flash tubes for 10,000 flashes. An active professional studio can reach this number of flashes in only a few weeks. We all know that Quartz flash tubes last for years, they just keep flashing. That's true but something does happen to a Quartz flash tube over a period of time and manufacturer is aware of these changes. Light output decreases by as much as 2 f-stops. Color correction coatings darken and can change the color temperature by as much as 800-1000 degrees Kelvin from its original color. All this happens over a long period of time, but when the light output decreases by 1 f-stop and the color changes 700-800 degrees Kelvin, it would be wise to replace the flash tube and save a critical assignment. You can test the flash tubes in your studio and keep records of each flash tubes light output and color temperature; it will take only a few hours of your time but save many hours of frustration in the future.

Testing for Light Output & Color Temperature

Equipment Needed:

1- Flash Meter

1- Flash Color Temperature Meter

1- Light Stand

1-Tripod

1-Power Pack

All your Flash Heads.

Let's start.

1) Set the power pack to full power position.

2) Place the first flash head to be tested on to the light stand and plug it into the power pack.

3) Place the flash meter securely on to the tripod camera platform pointing the dome directly at the flash head. Note: Do not use any reflector or other light modifiers as they can alter the readings. The distance is not critical but 6 feet from the flash head is a good location for the meter. If you get too close, the color temperature meter will give incorrect readings or no readings, as the full power output from the power pack will saturate the meter sensor.

4) Connect the cord from the flash meter to the power pack sychro socket. (If you are working with an assistant, cordless operation can be used.)

5) Set the flash meter for ASA 100 (or any ASA you desire), and the color temperature for 5500 degrees Kelvin.

6) Activate the flash meter by pushing the button and observe the reading, take another full power reading. Record the reading for flash head #A.

7) With the color temperature meter in your hand and standing at the tripod position, take a color temperature reading for flash head #A. Repeat the reading 2-3 times. Record the last reading.

8) Repeat this procedure for all the flash heads making sure that the flash meter is at the same distance and the power pack is at full power.

When testing is complete, you will know the exact condition of all flash tubes and if repeated every 2-3 months, you will be the one to make intelligent decision to replace a worn out flash tube. Remember 2 f-stops loss on a power pack brings the overall power to 300w.s. You paid good hard-earned money to get 1200w.s. So let's keep it by doing this simple test.

Courtesy of Larry Farrell, Sun Star Strobo Flash Lighting Systems

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