*my* SOP FEC's per-body:
20D+580exII: +2/3 with any kind of Omnibounce, +1/3 'bare-bounced', 0 to -1/3 straight- on
40D+580exII: +1/3 with any kind of Omnibounce, +1/3 'bare-bounced', 0 to -1/3 straight- on
1D3+580exII: +1/3 with any kind of Omnibounce, 0 to -1/3 in all other circumstances
As might be understood, these are *my* Standards to start with using E-TTL(II), Manual Exposure and Evaluative metering, during any shoot I vary FEC/Exposure/Metering as deemed necessary, but 'ya have to start somewhere'
...tiny €0.02 worth...
Kindest regards,
Max@Home