Saturday, April 6, 2013

Experiments with pre-flash long exposure

This is a small post but it's fun. I've been experimenting with taking a primary flash before a long exposure. Since only the foreground will reflect most of the light, during this instant it will appear significantly brighter than the background. Once the flash is over, you may move out of the way and wait for the light from the background to be collected. After playing a bit, the result is a nice balance of lighting between foreground and background allowing you to take part in your long exposures with no photo-shopping! Here are some results of this random fun.

An example of the process, with Jean Pierre and Sisi. The exposure time was 15 seconds but we really only had to remain still a fraction of a second. ~ taken with a canon IXUS 80 IS, 15 sec exposure at 200 ISO, f#2.8

The orion nebula with the trees in view. Note that had the flash not been used, they would have looked more like those in the background. The lighting allows a nice blend between nature and the sky. Note that you can see the Great Orion Nebula (to the lower left of Orion's belt) ~ taken with a canon IXUS 80 IS, 15 sec exposure at 200 ISO, f#2.8

This last one is awesome, which was a variant tried by Sisi. I'll let you guess what happened ;-)

Overall, this is a great technique. Why is this a DIY post? Because I'm still exhausting the uses of my cheap 4 year old point and shoot camera (still a grad student, not living with my parents and with limited budget :-|). 

Anyone can do this. You just need a camera with an exposure time that may be adjusted to a reasonably long time (here, at least 7 seconds was fine). If you don't have a flash, just use a few flash lights and shine them for a brief period. It's a pretty obvious technique for a professional photographer but not something a point-and-shoot owner would necessarily be aware of.

I have a few other projects here but I will log them once I get some more substantial results with my flimsy telescope :-D, and I have time (could we all not use a little more time).