{"id":3438,"date":"2022-05-25T22:40:01","date_gmt":"2022-05-25T22:40:01","guid":{"rendered":"https:\/\/jimhphoto.com\/?p=3438"},"modified":"2022-05-25T22:40:46","modified_gmt":"2022-05-25T22:40:46","slug":"how-big-is-that-fish-eye-really","status":"publish","type":"post","link":"https:\/\/jimhphoto.com\/index.php\/2022\/05\/25\/how-big-is-that-fish-eye-really\/","title":{"rendered":"How Big Is That Fish Eye, Really?"},"content":{"rendered":"\n
\"\"<\/figure><\/div>\n\n\n\n

I only recently started to understand the specs for fisheye lenses. <\/p>\n\n\n\n\n\n\n\n

I’m big on fisheyes – especially for glass-and-steel city scenes.<\/p>\n\n\n\n

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But the 8mm fisheye I used for that photo is big <\/em>and heavy<\/em>. Recently I picked up a vastly smaller lens, the Pergear 10mm\/F8 (it’s great<\/a>). The coverage of the 10mm was somewhat less than that of the 8mm, as I expected. But not, as it turns out, for the reason I thought.<\/p>\n\n\n\n

Some time later I decided to get a full-frame fisheye to use with my Nikon Z6. I chose the TTArtisan 11mm F2.8, a nice lens, more compact than the 8mm Rokinon despite being full frame. And here’s where I got confused. I’d just assumed the field of view was directly related to the focal length, like any other lens; so allowing for the 1.5x sensor size factor, I thought an 11mm FF lens would take in more than an 8mm APS-C. In fact, it took in a bit less. <\/p>\n\n\n\n

Here’s the deal: a fisheye lens also has a field-of-view<\/em> specification, in degrees, but I’d never paid attention to it. And that specification is the one that matters<\/em>. The stated focal length only applies to the center of the lens; away from there, the image is increasingly distorted as the lens departs <\/em>from that focal length. It’s that distortion that makes the lens a fisheye and allows it to take in something like a 180 degree field of view. So actually, who cares about the focal length of a fisheye? It just defines the perspective of a small area the very center of the photo. <\/p>\n\n\n\n


Here are images from each of these 3 lenses, taken from the same spot, annotated with focal length, sensor size and field-of-view:<\/p>\n\n\n\n

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The difference is easiest to see at the top – the image from the 10mm lens with the 150 degree angle doesn’t include the distorted arc of the highest beam. But the 11mm FF and 8mm APS-C lenses take just about the same picture (the differences are mostly due to hand-held shooting).<\/p>\n\n\n\n

Sure, it’s obvious when you think about it. I just hadn’t.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

I only recently started to understand the specs for fisheye lenses.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[651],"tags":[673,674,15,675,469,277,14],"post_folder":[],"class_list":["post-3438","post","type-post","status-publish","format-standard","hentry","category-photo-tech","tag-angle-of-view","tag-field-of-view","tag-fisheye","tag-focal-length","tag-lens","tag-photography","tag-wide-angle"],"_links":{"self":[{"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/posts\/3438","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/comments?post=3438"}],"version-history":[{"count":0,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/posts\/3438\/revisions"}],"wp:attachment":[{"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/media?parent=3438"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/categories?post=3438"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/tags?post=3438"},{"taxonomy":"post_folder","embeddable":true,"href":"https:\/\/jimhphoto.com\/index.php\/wp-json\/wp\/v2\/post_folder?post=3438"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}