## This Old US Army Camera Had a 100-Inch Infrared Lens and Required a Spotter

Check out this beastly camera used by Signal Corps during the Cold War. It featured a 100-inch infrared lens that was capable of seeing through over twenty miles of hazy air — perfect for capturing reconnaissance photographs of enemy strongholds. The camera was so massive that it required two people to operate: one to frame the shot, and one to snap the photo.

100-inches is 2540mm and the camera appears to use 4×5 large format film, so the equivalent 35mm focal length of this cannon-like lens is roughly 760mm.

Here’s a short video that shows the camera in action:

The black box in the top photo shows the 100-inch lens’ field of view. The bottom photo is the scene inside that black box.

There’s a picture of the camera in the Corbis archives as well. Here’s the original caption it was given:

A new camera equipped with a 100 inch infrared lens can look through atmospheric haze and record on film objects up to 30 miles away, a feat almost impossible in terrestrial photographic equipment previously. Developed by the Army Signal Corps engineering laboratories at Fort Monmouth, New Jersey, the camera provides the tactical advantage of being able to photograph targets many miles away in combat conditions.

Nowadays, you can buy lenses with even further reach that aren’t nearly as big, but you probably won’t be shooting the image on large format film…

(via Reddit)

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• Matt

How does 2540 on 4×5 become 760mm on 35mm format?

very good qestion

• Charles Mason
• sierrarobba

I want this in 4×5 size!!!!!!

• Eric Delmar

A “normal” lens on 35mm is 50mm, and on 4×5 is 150mm, so 4×5 needs 3 times for equivalence. The math in the article is approximately right. My math shows 847mm, but “normal” can be anything from 35mm to 50mm in generally recognized terms for 35mm format.

• 11

somehow I got 720mm.

2540 * 36/(5*25.4) .. using horizontal field of view as a constant..

• 11

To get the same image as above using a canon eos full frame:
Let us use horizontal field-of-view as a constant.35mm sensor width (EOS) = 36mm.
4x5film width = 5*25.4mm

Using similar triangles, to achieve the same field of view as that of 2540mm lens on 4×5, we would need
2540 * 36 / (5 * 25.4) = 720mm lens.

However, if we use the above camera and replace the 4×5 film with a 35mm sensor, the field of view would be much smaller, so the equivalent focal length is still 2540mm.

right/wrong?

• Ralph Hightower

That is pretty incredible. Plus, I love the style of the old newsreel commentary.

• E

Looks more like 5×7″ film to me.