I everyone, I'm having a problem with my Speedlite Canon 580 EX II with Canon 7D. I've made many test and discovered that: If I activate AF Beam Assist on 580 EX II most of photos get out of focus/blurry, if I disabled it, all goes well, but obviously I need the AF Beam Assist to focus where there is no or poor light. For exemple, I took 4 photos. First with AF Beam Assist On, then 4 more with AF Beam Off. Look at the results (I've focused inside blue circle (where exist a lot of contrast)) Conclusion: When I activate AF Beam Assist I have a back-focus issue. Any help? What can I do to solve this? Thank you very much.