Can I configure my Sony A57 screen and viewfinder display to brighten with a manual flash, just like with the popup flash?

When I pop up the built-in flash on my Sony Alpha 57, the LCD and electronic viewfinder brighten up a lot, so I can focus properly in low light situations. However, when I put on my Yongnuo 560 mkII, this doesn't happen. Is there any way to change this behavior or is it standard behavior when an external flash is attached? I looked at the camera settings, but didn't see anything that would appear to affect this and without this effect, I can't see anything on the screen or viewfinder.