I am looking for something that will act as a relay when it senses a photographic flash.

Is LASCR what I am looking for? I am a newbie and I am a bit confused. Thank you to anyone who can help me out.

 

These parts are easier to find or get substitutes for - http://ourworld.compuserve.com/homepages/Bill_Bowden/page7.htm.

 

Here are some circuits with phototransistors and LDR's:

http://home.cogeco.ca/~rpaisley4/PhotoDetectors.html

Because the photographic flash acts very fast you have to choose a fast phototransistor.