Hello All, I have been battling this cold and flu stuff and loosing.

Here is a pretty cool article on how to build a high-end flash sync.  Most non-powered flash syncs only work up to around 100 feet and are only sensitive to infrared light.  The designer of  this unit is a cave explorer and has put together a pretty impressive design.

The photo diode used in this unit is sensitive to both visible light and infrared.  As a result this unit can be used underwater.

The site owner still sells PCB boards and kits, and offers a commercial version called the firefly.

Nice documented site.

caves.org.uk/flash/slv023/index.html

caves.org.uk/flash/slv051/index.html

caves.org.uk/flash/newsletter.html