Re: Sony A57 Vs. A580
Why are you surprised? A57 should score 1/2 stop lower than A580 due to SLT mirror taking some of the light. This has been known since 2010.
For this 1/2 stop lower score, SLT offers a lot of other advantages (higher frame rates with AF, AF in video, EVF, lower shutter lag, no mirror blur, etc). I will take all these advantages for 1/2 stop lower score, which isn't even visible untill very high ISO.