Shooting through aircraft windows

[Brandon Esten]

Hey all, I recently took a flight on the new 787 Dreamliner and shot a few clips through the window. I found some really strange distortions that would be extreme at certain angles and seemed to disappear at other angles. At first I was freaked out that my lens was damaged somehow... it would not focus at infinity or any other distance to my satisfaction. Later, after the flight I confirmed it was not the lens. Not sure if this has something to do with the variable tinting on those windows or if it's something different like a coating Boeing put on there... anyone with any ideas on this? Most curious.

~B

 

[Brian F Kobylarz]

Brandon,

To start, aircraft windows are made from a lexan polycarbonate or acrylic. There are actually several layers where distortion can be introduced.

For example, on a 747, the outer layer is a stretched acrylic (0.35 thick). Next to it is a modified acrylic (0.22 thick) both are sealed together forming the primary and secondary pressure boundary.

An inner panel (the one you can touch) is a thin sheet of SE-3 acrylic. Depending on the aircraft manufacturer, a Lexan polycarbonate (aka high end plexiglass) may be the material of choice.

Unlike optical lenses where coatings are used to reduce internal reflections (among other artifacts), the coatings on aircraft windows are employed to reduce scratches. Also, acrylics are subject to "crazing" (those hairline cracks that form on the surface).

The more you shoot off-angle, the more distortion can be introduced to the image.

 

[M.Halsell]

Excellent Q & A.

 

[Mike Isler]

Brandon, the 787 windows are unlike the windows on most commercial airliners (like the ones Brian mentions above). The 787 windows don't have a window shade, so to "black them out", they are electrically dimmable. It's the material sandwiched in there that causes the issues you're noticing. Read about the windows here:

http://gizmodo.com/5829395/how-boeings-magical-787-dreamliner-windows-work

The windows, developed by Gentex Corporation and PPG Aerospace, are consisted of two thin layers of glass with gel wedged between them. Changes of voltage and current triggered by the pressing of button initiate chemical reactions in the gel to darken the window. It is the first electrochromic window in the world. Passengers in window seats have total control of the darkness of the window but flight attendants also have central control to override individual window settings when needed, such as keeping them clear during landing and taking off.

At the darkest setting, the window appears total black to anyone except the person sitting next to it. For this person, the window adds a purplish blue tone to the outside world, enabling the sight of ice covered ocean and the rigid mountains clearly.