Often while shooting from Kerry Park, I notice a ridiculous number of airplanes flying around. Two airports lie just south of the city, so there is a substantial amount of air traffic. I wanted to convey the sheer volume in a single frame and this is the best idea I could come up with. You are looking at about one hour's worth of chaotic patterns over the Jet City.
How it was made:
This was my first ever attempt at capturing a scene with such a lengthy exposure. During the planning stage, I wasn't sure whether this would work out or not, but it was worth a try. My equipment consisted of a sturdy tripod, my Canon 40D coupled with a 50mm lens, and a remote shutter release cable. It would be very difficult, if not impossible to take this as a single image. With the shutter open for an hour, the city lights would be completely blown out and the noise would be unacceptably high.
To get around this problem, a composite would have to be made by stacking a number of shorter exposures. As mentioned above, I have never attempted such a shot so quite a bit of experimentation was involved. Due to the fact that so many individual exposures were to be blended, it is absolutely critical that all the exposures are consistent and that they are perfectly aligned.
To achieve consistent exposures, I set the camera to Aperture Priority mode in order to maintain the same depth of field and if necessary, the camera could automatically adjust the shutter speed to accommodate changing light. To make sure the images properly align in post processing, the camera should not be touched. I used a remote shutter release and locked the shutter button down in order to reduce the time between exposures. Another precaution I took was to set the lens to manual focus just to make sure it wouldn't hunt before each picture was taken, as that could seriously compromise my chances of getting good results.
One problem that is created by stacking images taken of a moving object is gaps will appear in the light streaks during the brief time that elapses between exposures. My aim was to take the longest exposures possible as a way to reduce their number. I initially experimented with 30 seconds (the longest shutter speed on my camera before bulb mode). However, this shutter speed was too long and caused the buildings to be overexposed. I then tried closing the aperture down from f/7.1 to f/11 but this still didn't yield optimal results, as the airplane streaks were too dim and undefined because they were moving too fast for the sensor to gather light. I eventually settled for 15 second exposures at f/9 as the balance between properly exposed buildings, and streaks that were bright with limited discontinuities.
In the end, I decided that the buildings were still a little too much on the bright side so I took a shot that was 10 seconds with plans to manually blend it later on.
Creating the composite image was tedious but simple. The hardest part was having the patience to stack 120 layers - one at a time. It was easy because the process was repetitive and limited in steps. With each new layer, I changed the blend mode to lighten, which allows only for the highlights (airplane streaks) to be visible. I then flattened the image (in order to not overload my computer) and did it all over again with the next image. When all the layers were added and the composite was complete, I blended in the exposure designated for the building lights. The final step was filling in each of the gaps that resulted from between exposures.
For those asking about the EXIF data, just ignore it. It is only displaying information about the photograph that was taken for the city lights.
Thanks to everyone for the help in getting this to #1 in Explore!
Please check out the large version!
Prints available here: www.danseidmanphoto.com