Warning : the capacitors in a camera flash can hold up to 600 volts which can kill you ! Don't attempt this if you don't know exactly what you are doing !
I recently did some experiments with an older flash to see how easy it would be to boost the output of a flash . I measured the voltage at the base of the flash and it was 220 volts . My D50 is rated at 250 volts so I put it on the camera and fired it . Not very impressive .
Then I took the old capacitor from my SB400 flash and joined the capacitor wires to that instead ...
Much brighter though it did take 5X as long to charge up , it only has one AAA battery in it .
I then tried a more controlled experiment to compare it to my SB800 flash .
Then I left the original capacitor in the flash and added two more to give it a boost .
That made it more powerful than my SB800 !
My thoughts are that since the capacitor is basically a small 'battery' it will only accept the voltage the charging system puts into it and adding more 'batteries' means the same voltage but a higher current so the flash tube can fire for longer .
As with any flash you wouldn't want to fire it at that power too often
because the tube could overheat but it's certainly handy to know that you could boost the output of a flash by adding a capacitor .
I got hold of a 3500uf capacitor which is only about 4 1/2 X as powerful as a SB800 capacitor .
I wired it in parallel with the flash tube of my old Sunpak GT pro 4011 flash and tested its output compared to a full power blast from an SB600 .
It is considerably more powerful but I need to do some more tests with it to see how long the tube lasts . I imagine if it is anything like the duty cycle of a welder , for example , and the normal flash is capable of firing at full power 4 times in a minute then this would perhaps be able to fire once a minute for exactly the same heat build up . I suppose time will tell .
This afternoon I decided to put the new "mutant" flash through its paces to see what it could do .
I fired it about 15-20 times all together without giving it much time to cool down .
I took a few shots to compare it to the SB800 on full power .Ignore the background getting brighter , it was raining and the sun was coming out again . Concentrate on the foreground and shadows .
I used the D50 because it can sync flash at any speed .
I had the "super-flash" on half power which was half the capacitors in the original flash plus the 3500uf cap I added .
Then I moved up the driveway to really put it to the test ....
I then moved to the top of the driveway . And tried at 1/3200th sec .
I would imagine the flash tube will last as it doesn't appear to have suffered any side effects .
"Full power " is when the other half of the capacitor bank inside the flash handle is also connected.