What is the secret to taking a fabulous photos of car light trails?
First, set Your DSLR camera on Manual or Shutter Priority mode.
Second, choose a slow shutter speed.
Third, stay with the aperture in the mid range, start with f/8 and slowly increase the f number if needed.
Canon EOS 700D, f/11, 30 sec, ISO 100, focal length 18mm (Canon kit lens 18-55)
The same setting might not work for everyone. You have to experience it yourself what works for you in the that particular situation, because the speed of the cars and the ambient light all matters what will be your outcome.
Set up your camera on a tripod or on a hard surface , you are good as long as you are not hand holding your DSLR. Use a camera remote or built-in self-timer to avoid shakiness. Blurred images might be the result of camera shake.
If your tripod is not very sturdy and there is a wind you might wait for another day, when there is no wind (or try to put your camera on a hard surface).
Switch to manual focus or shutter p. mode, because you do not want for your camera to be in and out of focus all the time. Choose your focus point and lock it.
Your ISO setting should be as low as your camera could go. Because you are taking the photo with a slow shutter speed, you can now afford to use the lowest ISO setting possible which is in general ISO100, this way less noise will appear on your photograph.
Picture format? I prefer to shoot in RAW + JPEG or RAW so it is easier to edit in post production the white balance and the other artificial light effects.
Set your shutter speed low - start with 10sec - this will allow your camera to send enough light into the sensor. It will give cars time to move through your frame leaving behind light trails. Take test shots to see if you are happy with the result. Start experimenting increasing aperture and / same time decreasing shutter speed.
Also important how long light trails you would like to have on the picture. For shorter light trails use faster shutter speed like 4 seconds.
Canon EOS 700D, f/11, 2 sec, ISO 100, focal length 28mm (Canon kit lens 18-55)
On the photograph above I set my shutter speed for 2sec, this setting allowed me to even capture a bit of the cars.
Let's see some more examples:
Canon EOS 700D, f/22, 4 sec, ISO 100, focal length 70mm (Sigma 70-300)
Canon EOS 700D, f/22, 5 sec, ISO 100, focal length 70mm (Sigma 70-300)