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Report zooms in on giant camera resolution test charts throughout the US

By dpreview staff on Feb 18, 2013 at 20:21 GMT

Dozens of two-dimentional aerial photo calibration targets are scattered all across the United States, according to a report by the Center for Land Use Interpretation. Constructed mostly during the 1950s and 1960s, these large outdoor charts were used as 'a platform to test, calibrate, and focus aerial cameras traveling at different speeds and altitudes.' The report points out that although some of these 'charts' are still used for some optical camera testing and calibration, they are primarily relics of the past.

GoogleEarth image of a tri-bar array at Eglin Air Force Base, Florida.

According to the report, 'the 1951 Resolution Test Chart on which [these outdoor calibration symbols are] based is more than 60 years old and was designed for film cameras, and predates high-resolution digital systems and CCDs. The arrangement and spacing of the lines is not well suited for computer analysis (it's not a continuous single row, but two or three rows of pairs), and it has other frequency and modulation issues that make determining sharpness by digital means inaccurate.'

This ground-level photograph shows one of the giant calibration targets as it appears today, at Cuddeback lake in the Mojave desert.  [photo: CLUI]

The report mentions some targets specifically, for example, 'three Tri-bar targets remaining at Cuddeback Lake are visual analog relics of the aerial viewing revolution, and they may be the only ones on public land. With dendritic cracks filling with brush, breaking through the uniformity of the 5:1 bars (each bar and space between the bars is five times as long as it is wide), the flat surfaces are peeling, crumbling and sprouting, producing dimensionality, and relief.'

(via Petapixel).

Comments

Total comments: 26
Todd Ka
By Todd Ka (Feb 20, 2013)

Now they use your iphone screen when you are outside...

0 upvotes
Marty4650
By Marty4650 (Feb 19, 2013)

This pretty much explains those crop circles, that the Martians left so they could calibrate their telescopes from Mars.....

3 upvotes
midou
By midou (Feb 19, 2013)

interesting, could be an explanation for Nazca drawings....

0 upvotes
Juck
By Juck (Feb 19, 2013)

Keep wearing that foil helmet. lol

5 upvotes
Rick Knepper
By Rick Knepper (Feb 19, 2013)

I had to look up "dendritic".

0 upvotes
Shunda77
By Shunda77 (Feb 19, 2013)

I bet the Russians enjoyed using these for their spy satellites!

2 upvotes
Aaro
By Aaro (Feb 19, 2013)

Interesting targets scattered around, between very large to 1:1.

http://maps.google.com/maps?q=34.85889,-117.713013&ll=34.873539,-117.647438&spn=0.277442,0.528374&num=1&t=h&z=12

See big bad troll.

Best
Aaro

Comment edited 47 seconds after posting
0 upvotes
Paul Farace
By Paul Farace (Feb 19, 2013)

If you ever get to the USAF museum in Dayton, check out the Cold War gallery display on aerial/space photo recon systems... what they can show is AMAZING, both from a film standpoint (think roll film 20 inches wide and many yards long!) and a lens technology standpoint (ultra-precision lenses ground to exacting tolerances and they're the size of large trashcan lids!)... and that's what they CAN show us! So it's basically early 60s tech at best!

1 upvote
zbarr474
By zbarr474 (Feb 19, 2013)

Two other items:
The lenses were hand ground in Massachusetts, near Boston
The film speed during exposure was calibrated to the plane's speed which was generally an unarmed P-38.

0 upvotes
yudhir
By yudhir (Feb 19, 2013)

LOL ! I wonder how would they transmit back films.!

0 upvotes
Rob-uk
By Rob-uk (Feb 19, 2013)

They dropped the film in canisters which were collected by c130's.

1 upvote
Paul Guba
By Paul Guba (Feb 19, 2013)

Much of the how was just released to the public. Was an interesting story as there was a whole group of workers in Connecticut that worked on this project but never told anyone what they did. It really was amazing what they achieved within the limitations of the technology.

0 upvotes
Funduro
By Funduro (Feb 19, 2013)

Oh gee this will make the North Koreans jealous and set off another nuke.

0 upvotes
rfsIII
By rfsIII (Feb 19, 2013)

Who needs LensAlign anymore? I fly to California on Friday, and instead of sleeping I'll be calibrating my Nikkors.

Comment edited 48 seconds after posting
4 upvotes
Lan
By Lan (Feb 19, 2013)

The interesting thing here is not the test patterns themselves, but the size of the smallest details on the recent test patterns.

There's little point in having detail on the charts if it's significantly smaller than the cameras can resolve, so the finer test pattersn hint at some pretty detailed capture.

If they're no longer flying drones/plances, it suggests the maximum detail available from the military satellites must be rather high. I guess we knew that anyway, as the GoogleEarth is unlikely to show the best resolution on offer.

Then again it could all be a double bluff, and they may just want us to think that. Don't forget to pick up your tinfoil hats on the way out folks ;)

1 upvote
MarkInSF
By MarkInSF (Feb 19, 2013)

Out in the Mojave paint lasts a very long time. It's extremely dry and hot out there. I've seen painted signs that are far older than these charts. Colored paint fades, but white paint just gets dirty.

2 upvotes
Jim Evidon
By Jim Evidon (Feb 18, 2013)

Re.: Fresh paint on obsolete targets.
Bureaucracy, like nature, has certain immutable rules. One of those rules is that a bureaucracy, once created, can never be destroyed. Another rule is that a bureaucracy's budget, one created can be increased, but never be diminished.

As a result, there is, no doubt, a federal "Department of Resolution Test Chart Maintenance" which dutifully fulfills its destined mission and regularly repaints
and/or refurbishes these targets. It is, no doubt, manned and/or womaned by dedicated servants of the citizenry numbering in the hundreds to carry out its mission and its destiny. Said task force, speculatively, is primarily charged with records keeping, producing and updating mil specs for the specific paint required together with one painter and staff.

Comment edited 2 times, last edit 1 minute after posting
10 upvotes
photogalleryonline
By photogalleryonline (Feb 19, 2013)

Wheres the guy to mow the grass but!

0 upvotes
Benarm
By Benarm (Feb 18, 2013)

Big brother is literally watching you. ;)

2 upvotes
huyzer
By huyzer (Feb 18, 2013)

Wow, very neat.

1 upvote
wilerty
By wilerty (Feb 18, 2013)

Interesting. The paint on those targets is not from the 50s or 60s, so somebody must be using them ...

1 upvote
mauijohn
By mauijohn (Feb 18, 2013)

There are two of them in the desert. about 4 miles west along the side of that road.

0 upvotes
bizi clop
By bizi clop (Feb 18, 2013)

These patterns still could be used to calibrate or compare Google/Bing Maps.

4 upvotes
Tan68
By Tan68 (Feb 18, 2013)

interesting snippet, though.
like something from damninteresting.com

0 upvotes
Tan68
By Tan68 (Feb 18, 2013)

Nothing explains the guys leaning out while someone holds their belt so they can look straight down from the Empire State building. It is all frenzy, wrapped in absurdity, inside a compulsion.

0 upvotes
mike kobal
By mike kobal (Feb 18, 2013)

this finally explains the long lines of photographers with cameras around their necks patiently waiting to get to the top of the Empire State building, so many cross walks and patterns, perfect for focus calibration!

Comment edited 3 minutes after posting
3 upvotes
Total comments: 26