Upload & Sell: On
I have a 580EX that I purchased used (like 2 others I have) and at the time I didn't notice it was having an issue. I suspect now (months later) that the seller knew it had problems...
Why do you suspect that?
...Anyway. The problem is it refuses to fire off a charge less than about 1/4 power. In manual mode, at 1/128 power, it fires 1/4 power. At 1/64 power setting, it fires about 1/2 power. At 1/32 power setting, it fires full power. Any setting above that fires full power. It fires at these power levels with the test button or on-camera in manual. In eTTL mode on-camera, it consistently overexposes if the shot requires less than 1/4 power... Ever hear of this problem? Clearly I got ripped off by the seller...
Not clearly at all.
...but if anyone is familiar with it perhaps at least I can have some idea of what happened and possibly how to go about fixing it.
The power level of Canon Speedlites is varied by quenching the flash early, via a device called an Insulated Gate Bi-polar Transistor (IGBT). The IGBT gets its instructions from a logic circuit that gets information from either the camera's built-in flash meter or from the Manual Power Level setting.
If any of the circuits develops a fault, it can manifest in precisely the issue you describe. The only way to fix it that I know of is to replace the faulty circuit(s). A trip to Canon may cost less than getting a replacement flash, but a call to them would confirm that.
Good luck; I hope you can get it fixed without too much trouble.
Edited on Apr 09, 2012 at 12:34 AM · View previous versions