Fresnel Lens, 15 January 2011


As a photographer, I suppose it is unsurprising that I would be enamored of all manner of precision optical equipment. The following is no exception!






Photo Information:

Location: Portsmouth, Virginia
Camera: Nikon D80
Lens (Upper 3 photos): Nikon Nikkor 60mm f/2.8 Micro
Lens (Lower 2 photos): Nikon Nikkor 85mm f/1.8
ISO Equivalency: 100
Color Setting: Vivid (Black & White conversion in post-processing)

The subject of this series of photos is the massive Fresnel lens [1]Ā that was originally installed at the Hog Island Light [2] on Virginia’s Eastern Shore. [3] This particular example is what was known as a first-order lens, which basically means it was one of the largest of its kind – and I can attest to that…standing next to it, the entire construct was very likely at least 10 feet tall. The Hog Island Light was decommissioned in 1948, and the Fresnel lens now sits in a replica housing near the Elizabeth River in Portsmouth, Virginia. Oh, and it still rotates!



[1]: Simply put, a Fresnel lens is a “collapsed” spherical lens, where the curve of the lens has been “cut” into concentric rings with only enough optical material (glass) being utilized to create the curved portions of the lens. The end result is a lens that not only weighs far less, but also takes up far less space than a traditional spherical lens. They aren’t suitable for use in cameras, though, since the concentric ring segments would be visible on the film (or digital sensor), but a lighthouse beam isn’t constrained by this, since all it needs to do is make a very bright beam of light that can be seen from miles away. See here for additional information (Wikipedia article).

[2]: See here for additional information (Wikipedia article). Obviously with the advent of GPS technology, lighthouses are no longer necessary for nautical guidance, though the Hog Island Light met its demise the old-fashioned way: erosion.

[3]: Look, if I have to tell you where on the Eastern Shore this lighthouse originally stood, well. Let’s just say you’ve got issues, and leave it at that.


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