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Canon 580EX-ii flashing only at full power despite different regulation ETTL, reduced power manual


After working properly for many years, my Canon 580EX-ii suddenly started flashing only at the maximum power. I tried many options, including the following:

- tried to use it on 2 different cameras (Canon 5D Mark II, Canon 7D),

- reset all the factory parameters to 0 (zero)

- tried to us ETTL, TTL, manual mode: in any case it flashes at the maximum power

Apparently it is not a matter of improper setting. Anybody could tell me which should be the damage? Thank you for your support. Nicola




Does the flash work correctly when the camera is set to Full Auto. Full Auto locks out any changes to settings on the speedlite. Unlike the Creative Zone ie (M, Av, TV & P) modes. Also with the speedlite set to TTL. The speedlite will always fire at full output. TTL is ONLY compatible with EOS film bodies. The last 2 or 3 Canon film bodies are ONLY compatible with E-TTL. The cameras will act like EOS Digital cameras when set to TTL. If the speedlite is NOT communicating with the camera correctly. The speedlite reverts to TTL. 


Current Gear: EOS 5D Mark IV, EF Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM