General Flash Question

i have (2) 580's and i notice one is brighter then the other, i use one of them most of the time, second as back up.....my question is, over time can a Flash lose its brightness? And whats the life expectancy of a flash?

yes, i had both flash w identical settings.

your thoughts...


-EK

Interesting.

They have a plastic front lens that over time will Yellow with exposre to the very hot light, as well as UV from sunlight.
Do both of them have a clean white front lens?

I assume your firing both of them from a full discharge?
Its possible that one isn't fully charging because of lower spec batteries.

And of course, I assume you have checked the FEC is the same on both units?

And, do you have any sample photos?

In addition to what was just said, I wouldn't rely on visual alone. Put a fresh set of batteries in each one and using a flash meter quantify the maximum output of each. Just test fire each one at the flash meter from the same distance. Let us know what the f readings are for a set ISO and shutter speed.