Light Trails are created when you use keep the shutter of your camera open for a long period of time. I have always wanted to try my hand at this process but really with 2 kids under 5 it has been hard. Finally the little people that sit under my desk released the shekels and I was able to go out and practice this process. I had to pack my gear and FAST this is what I took with me
50 mm lens
shutter release cable
mp3 player and bottled water (for personal entertainment)
So I started out by picking a spot that was safe. As you can see it was night roughly 9pm and I didn’t want be missed or put in any compromising positions. So please when you’re doing any type of Night Shoots keep this in mind SAFETY FIRST.
After I set up my gear I put my camera on the Bulb (B) setting which is your shutter speed. My F-stop settings I played around with quite honestly till I found one that I liked. [the settings used are documented under each picture]
As the cars pass by the front of my lens both the rear and front lights draw lines across your sensor sort of like an etch a sketch. Because there is no other light to compete with the cars, you get light trails that go on for as long as your shutter is open. So, in order to get light trails, you need moving light sources, and you need to keep your shutter open long enough to capture their movement, usually 5 seconds.
I think the easiest way it to just have fun and play around till you get something you like. I used a shutter release cable and just, in the end play around with the technique for a few hours. I found my sweet spot was using my 50mm at F/10 ISO 800 for 4 seconds.