On Tue, 18 Jun 2013 21:18:26 -0700, Savageduck
wrote:
: On 2013-06-18 19:52:12 -0700, Robert Coe said:
:
: On Sun, 16 Jun 2013 21:52:11 -0700, Savageduck
: wrote:
: : On 2013-06-16 13:11:29 -0700, Robert Coe said:
: :
: : On Sat, 15 Jun 2013 11:51:19 -0700, Savageduck
: : wrote:
: : : On 2013-06-15 09:25:16 -0700, said:
: : :
: : : I can find the Nikkor 14mm f2.8 but I'd REALLY like something with fair
: : : to excellent image quality (point spread OK) AND a low F# ... lower
: : : than 2.8. HELP!?? Vintage lenses OK.
: : :
: : : Why do you need a "fish-eye" faster than f/2.8?
: : :
: : : The Nikkor 14mm f/2.8 is not a "fish-eye" it is an ultra-wide angle
: : : lens. There is more to a "fish-eye" lens than just being a wide angle.
: : : Typically the idea is to capture a 180 degree field of view and that is
: : : usually attained by a combination specialized lens construction
: : : imparting a spherical distortion beyond that imparted by an ultra-wide
: : : angle.
: :
: : I'm far from an expert in optics, but I was under the impression
: that it's the
: : other way around. I.e., an ultra-wide-angle rectilinear lens requires more
: : drastic corrections, because ultra-wide lenses naturally tend to be
: fisheyes.
: : Am I misinformed? (The Wikipedia article is vague on that point and can be
: : read either way.)
: :
: : Bob
: :
: : I don't own a fish-eye, but I have my Tokina 11-16mm f/2.8 which at
: : best is going to give me a 104-84 degree angle of view, and it is no
: : fish-eye, but is well described as an ultra-wide angle. My expectation
: : of a true fish-eye lens would be to get as close to a 180 degree angle
: : of view as possible, and deal with the associated distortion.
: :
: : The Tokina 10-17mm fish-eye meets those expectations with a 180-100
: : degree angle of view.
:
: What you're saying is that the 11-16 is a rectilinear lens, while the 10-17
: isn't. I'm suggesting that the 10-17 was probably easier to design and that
: the more UW an UW lens is, the closer it is to a true fisheye by default. I've
: always understood that to be the case, but I'm not a lens designer.
:
: Bob
:
: The 10-17mm FE was probably easier to design, and certainly the
: rectilinear nature of the 11-16mm is complex and performs very well
: within its design criteria.
:
: ...and yet the ultra-wide 11-16mm is 76 degrees in AoV away from being
: labeled a fish-eye.