I just bought the sunpak MZ440 flash to improve my night shooting.What I experienced is that no matter the distance the object is, the aperture is always sets at the camera aperture with the attached flash (Without the sunpak max at f4.0 of ISO400), and this has caused serious overexposed of the picture. The camera does not follow the aperture as shown in the slide table within the Flash body. Can anyone help explain why such thing happen and how to rectify it ? The autofocus seems to work alright.

-- S. Masri (masris@telkom.co.za), December 07, 2000

Answers

I'm not sure why your flash pictures are overexposed, but it sounds like your flash is working the way it's supposed to. With the MZ440 the aperture will probably always remain wide open or at some specific setting. The camera regulates the exposure by reducing the amount of light the flash puts out, not changing the aperture of the lens. The flash duration changes based on distance and reflectivity of the subject, but the aperture will stay the same as long as the ambient lighting is fairly dark.

If you had a Canon EZ series Speedlite (420EZ, 540EZ, etc.) there would be a preflash that would cause the camera to reduce the aperture in most situations. That's what A-TTL flash metering does. I don't think there are any non-Canon flash units made that will do A- TTL though. So you're stuck with plain old TTL flash metering.

You can try doing what the A-TTL scheme does though. Set the camera to manual or Av mode and reduce the aperture yourself. You don't have to be accurate, the flash mettering system will make the needed compensations.

Most flash overexposures in TTL mode are caused by the subject being too small or off center. The camera trys to make a larger part of the central area lighter and if the subject is not there or is filling too small an area, it gets overexposed.

-- Jim Strutz (jimstrutz@juno.com), December 08, 2000.