Angular field of viewcalculator

How to use the table: Hopefully the table is quite self-explanatory, but let's say you are looking for the Field-of-view of a 50mm lens mounted on an FX body. In the column "Lens Focal Length", go down to the row marked "50mm" and then over to the green area marked "35mm & FX format (1)". The FOV for a 50mm lens would be 39.6 degrees horizontally and 27.0 degrees vertically. Diagonally, the FOV is 46.8 degrees.

Field of viewhuman eye

For a 55mm lens on a APS-C/DX sensor format body, the field of view would thus be 24.0 degrees horizontally, 16.1 degrees vertically and 28.7 degrees diagonally.

Fresnel lenses came in several sizes, or orders, from the largest, the Hyper-Radial, to the smallest, the eighth order. Not all orders were used in the United States. Large first order lenses, such as those still in place at the Fowey Rocks lighthouse in Biscayne National Park or the Bodie Island lighthouse in Cape Hatteras National Seashore, were usually used on major seacoasts, with a more powerful beam that shines up to twenty-one miles out to sea. Fifth or sixth order lights, the smallest used in the United States, were used in smaller bodies of water, such as bays or rivers. The Jones Point lighthouse on the Potomac River in Alexandria, Virginia, used a fifth order lens for the comparatively smaller distances it had to cover, but it was nonetheless essential to the hundreds of merchant, passenger, fishing, and naval vessels that traveled the waters around Washington, DC daily.

Please note, this is a table of rectilinear values, i.e. values for rectilinear lenses; fisheye field of view is a different beast.

Angular field of viewformula

Mark Brickley (mbrickley) on November 9, 2024 in A Visit to the Falkland Islands and the Antarctic Peninsula

Angular field of viewvs fov

The Fresnel lens (pronounced "Frey Nel"), as it came to be known, represented a monumental step forward in lighthouse lighting technology, and therefore also in maritime safety. In a Fresnel lens, hundreds of pieces of specially cut glass surround a lamp bulb. This design intensifies the glow from the light, focusing rays of light that would normally scatter into a single, intense beam of light, which shines out in a specific direction. The lens could produce an unlimited number of flashing combinations and intensified the light so it could be seen at greater distances, allowing mariners a greater deal of safety in their navigations near shore.

Panorama made of 12 vertical shots stitched together Nikon D70 with 12-24mm f/4G ED-IF AF-S DX Nikkor @ 12mm, f/7.1, 1/60s With hand-held SB-800 on SC-29 cable, TTL|BL flash setting

Fresnel lenses may be fixed, showing a steady light all around the horizon, or revolving, producing a flash. The number of flashes per minute is determined by the number of flash panels and the speed at which the lens revolves. A unique flash pattern for each light is produced by varying the amount of light and dark periods. For example, a light can send out a flash regularly every five seconds. Alternatively, it might have a ten second period of darkness and a three second period of brightness, or any number of other combinations. The individual flashing pattern of each light is called its characteristic. Mariners consult a light list or a maritime chart that told what light flashes that particular characteristic, and what color the light is. This allowed them to determine their position at sea in relation to the land.

Field of viewcalculator

Angular field of viewconverter

Nearly all lighthouses in National Park units originally had a Fresnel lens, though many of them have been removed and/or replaced with more modern lighting mechanisms. However, the lenses’ beauty and their pivotal place in lighthouse history has ensured their preservation in many instances. Some are in museums associated with the historic lighthouse itself; others are in museums away from the lighthouse. And of course, there are many, many more Fresnel lenses in American lighthouses that are not part of National Parks. The United States Lighthouse Society maintains a large amount of information about Fresnel lens history and technology, as well as lists of current and operational Fresnel lenses in the United States.

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The values for Field of View (FOV), sometimes sloppily referred to as "lens view" or better, "angle of view", come up frequently enough at the forums that I thought a list might be helpful for quick reference.

Most Fresnel lenses look like a beehive or barrel; most contain from two to twenty-four different panels. A clock type mechanism, which had to be wound by hand every few hours before automation, was used to make the revolving lenses rotate around the lamp itself to produce the flash. The movement of the lens is timed precisely so the panel will pass by when a flash is due.

Heinz Augustin (richmondguy) on November 20, 2024 in A Visit to the Falkland Islands and the Antarctic Peninsula

The use of lenses in lighthouses began in England in the 18th century, and was adopted in the United States by 1810. These early lenses were thick, excessively heavy, and of poor quality glass. Therefore, they were not very effective and prone to losing the light through the thick glass. In 1811, the French Commission on Lighthouses established a committee to investigate improvements in lighthouse illumination. Among the committee members was Augustin Fresnel, who in 1822 completed the design of his flashing lens using thin bull’s eye shaped panels, which refracted the light both horizontally and vertically, producing a much stronger beam of light.