Questions I had about camera flash but never asked..

[tea man]

I've never been a big user of the camera flash and I've toyed with

my Metz on the rare occasion. I've always had questions..

 

1) If the flash is kept unused, I'm told that its output diminishes

if you don't maintain it by firing it ocassionally. Is this true?

How?

 

2) I'm told that you can damage the flash unit if you cover it with

while its being fired. Can you? Why?

[jmf]

1. true. The capacitors which store the charge become degraded. Usually 10 or so full power pops will bring them back to life. I'm not sure of the physics/chemistry, but it's true of studio flashes too. It's sometimes refered to a "forming" the caps.

 

2. Heat buildup, but I doubt 1 or even a few pops would be an issue.

[gaius1]

2 is probably true, just due to heat buildup, but regular diffusers and the like should be fine.

[lex_jenkins]

Yup, the capacitors need to be reformed after disuse. Most capacitors are good for many years before they need to be replaced (or the unit simply discarded). The only devices I've seen that needed replacement capacitors were old boat anchor tube ham radios and shortwave receivers. I have a 25-year-old generic auto-thyrister flash that took a swim in the Guadalupe River during a canoe trip. It still works, even after emitting a pop, crackle and puff of smoke about 10 years ago when I first tried lithium AA batteries in the flash.

 

And, yup, flash units can be damaged by heat buildup from continuous firing. This includes battery powered hotshoe flashes, monolights and pack lights. The manufacturers will advise how many consecutive shots within a fixed period of time is appropriate before the unit must be allowed to cool.

 

Nikon suggests a maximum of 15 consecutive shots at full output at 6 frames per second before allowing the flash to cool off for 10 minutes. With various partial discharge settings the flash can be fired up to 40 times before a cool off period is needed.

 

I would expect that most similar units have similar restrictions. Quantums and other portable flash units may allow more shots between cooling.