Sunday, February 4, 2007


Well, it looks cooler but seems less useful than I thought it would. In analyzing the footage from the Pentagon's CCTV security cameras, I had been concerned with the distorting effects of the fisheye lens, the kind like on your motel room door. The cameras are designed to monitor car traffic coming into the northwest entrance, but do have a good view to the south of the large west lawn and heliport. Here is an original, uncorrected shot of a police car pulling into the gate just seconds before Flight 77 screamed across the lawn. The red lines show distortion caused by the lens.

I opened the shot in Photoshop, used an elliptical selection tool lined up with the rounded corners at the bottom, and applied the spherize filter, full inversion (-100%) and got this, again with lines to show the correction. It's not perfect, but helps some.
The rooflines still has a bit of a curve to it, so I tried anti-spherizing it again.

And clearly this isn't helping much. It also appears the effect diminishes with distance. Countering the fisheye effect on the white blur frame itself doesn't add much to our analysis except shrinking the scene some and starting to distort the plane with the edge effect. I'm not even going to bother showing separate frames for comparison - here they all are together: lowest level is uncorrected, middle layer de-spherized once, top layer done twice.

No comments: