The World's Largest Lens Test Chart

...Is the world, turns out.

Many of us have seen the familiar tri-bar patterns on lens test charts, like the ones based on the 1951 USAF Resolving Power Test Target you once could buy out of the back of Modern Photography magazine to tape to the wall and perform a series of fun but semi-useless tests of your lenses' sharpness. (Your photo buddy, Poindexter, was always quick to point out that he used newspaper instead, because Poindexter never "wasted money.")

GoogleEarth image of an expanded tri-bar array at Fort Huachuca, Arizona.

Well, it turns out there are huge tri-bar patterns painted on patches of tarmac and scattered hither and yon about the country. Many are in the Mojave desert, and are believed to have been used to calibrate the lenses of spy cameras aboard things like the SR-71 Blackbird and the U-2 spyplanes in the 1950s and '60s.

You have to have a geek streak to find the post about it at the Center for Land Use Interpretation website interesting, but I did, and you might.

Die Welt ist merkwürdig.

Mike
(Thanks to Matthew Blair)

Original contents copyright 2013 by Michael C. Johnston and/or the bylined author. All Rights Reserved. Links in this post may be to our affiliates; sales through affiliate links may benefit this site.
A book of interest today:

(To see all the comments, click on the "Comments" link below.)
Featured Comments from:

Gordon: "Are there also hidden but giant brick walls for them to do distortion tests on as well?"

Mike replies: There's the great wall of China, but it always shows mustache distortion.

Comments

[Chuck Albertson]

I'd wager the spooks aren't too concerned about the bokeh of the lenses on their U2/SR71/Keyhole cameras.

[Chris]

The funny thing is that for earth observation satellites - just like with ordinary photographic equipment - color usually requires much more consideration for calibration than spatial resolution. For spectral calibration of satellites natural features with known spectral properties are most common but artificial test targets are also known to be used. So it is not too far fetched to look for a giant GretagMacbeth color checker somewhere out there (although it would most likely primarily contain infrared colors).

[richardplondon]

Does anyone have an explanation of these patterns - ?

[Rod S.]

That image certainly is a striking one, Mike.

Yes, an interesting article. Must appeal to all us middle-aged readers of 1970s Modern and Popular Photography.

[J]

Ft. Huachuca is the Army test center for communications. I have been there many times training them in fiber optics. Here is where they test many experimental comm systems in secret so I assume this is a phased array antenna or similar.
BTW, you can visit this "Hell hole" and see the museum of the "Buffalo Soldiers" - the first black soldiers in the US Army.

[David L]

Don't forget the Corona spy satellite program of the 1960s. Corona satellites used two oscillating cameras to expose kilometers of 70mm film, which was subsequently parachuted back to earth and caught in mid air by aircraft trailing tripwires. Wikipedia has a good description.
By the end of the program, resolution had improved to around (and probably better than) 2 meters. These images are now gold for archaeologists.