Roads in the Sky

dseidman · Mar 8, 2009

Hey guys! Here's my first post on these forums.

This is about an hour's worth of air traffic over Seattle. I'd love to know what you think!

beni_hung · Mar 8, 2009

Awesome! Very creative! I would love to know how you did it :mrgreen:

Josh66 · Mar 8, 2009

That is awesome! I don't think I've ever seen a photo like that before.

K8-90 · Mar 9, 2009

Whoa!

...

Whoa!

dj741 · Mar 9, 2009

Love it! Looks really space age.

quickshot · Mar 9, 2009

This is soooo neat! I see a lot of people using timed exposure to do roads at night, but never the sky. How awesome!

Al-Wazeer · Mar 9, 2009

AWESOME!!!

HOW DID YOU DO THAT?!!

dseidman · Mar 9, 2009

Thanks to everyone for stopping by! I've had the question asking how this is made posed to me many times so I wrote up a description a while back. Here's the 'how it was made' description copied from my Flickr account:

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.

I hope this helps.

LaFoto · Mar 9, 2009

Welcome to ThePhotoForum, thank you for this quite unique photo, and thank you for the description of how it was made, too!
The description sure helps a lot!
It also tells me that I probably won't ever have the patience to copy this photo of yours ever (in my part of the world), as merging 120 exposures into one sounds REALLY tedious, although I must say: the result is WELL WORTH it!!!! Way cool!

polymoog · Mar 9, 2009

Awesome image, and thanks so much for explaining how you did it

dseidman · Mar 10, 2009

LaFoto said:
Welcome to ThePhotoForum, thank you for this quite unique photo, and thank you for the description of how it was made, too!
The description sure helps a lot!
It also tells me that I probably won't ever have the patience to copy this photo of yours ever (in my part of the world), as merging 120 exposures into one sounds REALLY tedious, although I must say: the result is WELL WORTH it!!!! Way cool!

Tedious indeed! Usually I'm pretty lazy and would never spend so much time on a photo, but this time I was feeling really inspired to try out this idea of mine. I'm glad you like it!