Although fisheye lenses are of a specialised nature, clearly there is a demand as there are so many available, at all price levels. However, there are very few fisheye zooms and even fewer lenses that offer the choice of a circular 180-degree image or a full frame 180-degree on the diagonal image. It looks to be a fascinating concept, so let’s see how it works out in practice.

Handling and Features

First, the technical bit. Fisheye lenses come in various types, the obvious one being that they can offer circular or full frame images. This zoom offers both, on full frame sensors a 180 to 175-degree image and on APS-C 180 to 110 degrees. There is also the question of the projection of the image, much in the same way that maps have a projection to put a round globe onto a flat piece of paper. This lens is the most commonly used type and has an equisolid angle (equal area) mapping function. A Google search will find the mathematics of this for those who wish to pursue it further.
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https://www.ephotozine.com/article/nikon-af-s-fisheye-nikkor-8-15mm-f-3-5-4-5e-ed-review-31272