Vivitar 3500 Thyristor Flash

I have two Vivitar 3500 flashes (one is a 35-D, but they are identical as far as I can tell). For the longest time I could not figure out how these things actually worked. There are four settings on back; red, blue, orange, and manual. From the 'calculator' up top you can tell the three color settings are two stops apart, and manual is full power. But until recently I did not know that there is a photo resistor up front which actually adjusts the power of the flash based on the amount of light the sensor sees. The more less light, the more resistance, and the stronger the flash. Thanks to this discussion on the Strobist Flickr discussion group I was able to get a better understanding on how this flash works. I decided to set up an experiment to see how this sensor works in practice. This will apply to all Vivitar thyristor flashes.