Napioa - Wind Origins

Napioa - Wind Origins
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May
1
asked How does lateral chromatic aberration correction without a lens profile work?
Apr
28
answered Can cameras set exposure in more precise increments than third stops in automatic exposure mode?
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 252 characters in body
Apr
26
comment What is the relationship between field of view and focal length for fisheye?
@Brandon The inverse of what you mentioned: 2 arctan(r/f), where r = 15 mm is the half-diagonal of APS-C.
Apr
26
accepted Prevent Lightroom from discarding lens model from EXIF
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 132 characters in body
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
edited body
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
edited body
Apr
26
comment What is the relationship between field of view and focal length for fisheye?
@scottbb Well, yesterday I made an embarrassing mistake when I forgot that 1/2 factor from inside of the sine (see my comment on the other answer). If I had found that mistake earlier, I would have deleted the question ... I was worried about backlash. I don't care much about reputation score any more, so CW is okay.
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 183 characters in body
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 679 characters in body
Apr
26
answered What is the relationship between field of view and focal length for fisheye?
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
deleted 617 characters in body
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 112 characters in body
Apr
26
revised What is the relationship between field of view and focal length for fisheye?
added 600 characters in body; edited tags; edited title
Apr
26
comment Prevent Lightroom from discarding lens model from EXIF
@Linwood You are correct. It is that bug. The information is missing for all lenses, not just this Tokina, but I didn't realize this ... If you write it as an answer, I'll accept. Or maybe I should just delete the question?
Apr
25
revised What is the relationship between field of view and focal length for fisheye?
edited tags
Apr
25
comment What is the relationship between field of view and focal length for fisheye?
I found this page which claims that the distance r for a point from the image centre is r = 2*f*sin(θ/2), where f is the focal length and θ is angle measures from the optical axis for that point. But it doesn't add up. Equal-area projection lenses that have a 180 degree diagonal FoV tend to have ~10 mm focal length (like this Tokina or the Nikon 10.5 mm). According to this formula they'd have a 20 mm radius 180 deg image circle. But the half-diagonal of APS-C is only 15 mm...
Apr
25
revised What is the relationship between field of view and focal length for fisheye?
added 241 characters in body
Apr
25
comment What is the relationship between field of view and focal length for fisheye?
What you wrote is valid for a rectilinear lens, i.e. for projection through a point. It also needs a factor of 2 in front of the arc-tangent. But this is not a rectilinear lens, far from it. Hence my question.