I have a 90mm Vivitar macro and ring flash on a Nex 6. Very dark viewfinder unless ISO is up fairly high and f-stop quite wide. The resulting shot with flash is also almost as dark as scene in viewfinder. It seems that the viewfinder isn't reflecting the light that is actually there. I've had the flash set to constant on and still the same result. This worsens when the magnification is higher as expected, but it seems that the sensor isn't seeing what's there. I have all settings at manual. Front curtain off, DR off. Any advice? Thanks!