I found this for a Sunpak flash which is similar to the G4500dx:
Reading from the "auto555/G4500DX" Manual, you need to:
1. Slide the Film Selector to desired ISO - (that is the same as your camera ISO used - so, make sure you turn Off the Auto ISO feature if your camera has one).
2. Slide the Mode Selector to "A" (Auto position). This will be Auto Thyristor mode on the flash.
3. Slide the Auto F/stop Selecct Know to desired lens openning - ( so use your camera in Aperture priority mode, more in Manual to prevent changes in the camera aperture value during shooting)
Shoot, and be happy with well exposed pictures by the Auto Thyristor features of the Sunpak 555 flash.
The Sunpak 555 works great with Nikon D50, D70 cameras, as you can synchrinize flash practically at all shutter speeds. Excellent for sunny days to get narrow DOF, yet get any ambient light level contribution as desired.
For other cameras, make sure (watch out for) that Aperture Priority mode does not use shutter faster than the camera max X-sync speed - so Manual camera mode could be a better choice for a novice photographer.
In the manual there is also a list of accessories for various brand cameras, How to use Power Ratio in Manual mode, some advice on using wide lenses, how to care of your 555, and Specification section.
Minimal flash duration is 1/450 at full power, so you can safely use Auto Aperture up to 1/500 sec. Flash duration decreases with lower power setting, or lower auto mode need for poser, and the shortest flash duration is 1/17000th sec.
on Jan 29, 2016