Aerial photography can be a fun adventure. Google Earth is often used by planners and engineers for images, however, there are times when specific angles of view can only be seen from a low flying aircraft.
Recently, I had a client contact me wanting photos of downtown Louisville, Kentucky for the pending new bridge that is to be built between Louisville and Jeffersonville, Indiana. The angle of view was critical because the photo would be used to develop a three-dimensional illustration of the additional bridge to the metropolitan area. Google Earth just wasn’t offering the client what they needed. What complicated the situation was the fact the site needed to be photographed during the day and at night.
Often, aerial images can be made from a small fixed wing airplane on a bright sunny day. Easy task. Flip the window open, direct the pilot where you need to be, shoot with a high shutter speed, and you are pretty much guaranteed success. Shooting that same image shortly after the sun has set requires a different skill set and equipment.
Since I had to replicate the photo as close as possible with and without the sun, I decided to use a helicopter for the shoot. Choppers are a much more stable platform to shoot from, especially when you have a good pilot. They are also quite expensive to rent, around $900.00 per hour. The pilot and I did a good deal of planning before climbing in to the big bird. We discussed the exact location and altitude and the time of day to execute both shots over the Ohio River.
The first flight was in the early afternoon with full sun on the city of Louisville and the Ohio River. I used a Nikon DSLR with a 50mm. lens to frame and photograph the proposed bridge route. Since the airport is close to the river, this only took about 20 minutes. I preserved the balance of my one hour budget for the evening photo. The pilot and I began our second flight about 15 minutes after sunset. At this hour, there is enough light to see the river and the buildings, but it looks “dark” for all practical purposes. Don Jeffries, a very accomplished helicopter pilot, positioned us again over previous landmarks and at the same altitude to pull off the duplicate photo. Using the same camera and lens, I boosted the light sensitivity of the camera (ISO) to 2000 and shot the image with the aperture set on f2.0. This allowed me to select a shutter speed of 1/640 of a second. This shutter speed allowed me to hand hold the camera and shoot multiple images. I only needed one sharp image to match the daytime shot.
True, the daytime photo has better image quality because of using a low ISO earlier, however, the high ISO image of the evening allowed me to make the photo that my client needed.
The following day, I sent several “select” photos to the out-of-town client by way of a FTP site. Within 24 hours of the aerial shoot, the client was putting the images to use for the 3D drawing.
Oh, the technology that we have today!!
Downtown Louisville Kentucky and the Ohio River with Jeffersonville Indiana in the foreground, night view.