Joined the Zenitar Club [img]

Started Sep 27, 2005 | Discussions thread
Lance B Forum Pro • Posts: 30,920
Re: Joined the Zenitar Club [img]

John Bean (UK) wrote:

Lance B wrote:

And PTLens does a bloody good job too but it ends up being a gnat's
c*ck narrower FOV than the DA14 unfortunately.

Is that using the "fisheye" option and manual cropping Lance? The
auto-cropped version using the profile loses a lot of HFOV.

Hi John,

I manually set the distortion to about 85 and the crop to 8 which does take impact on the HFOV. From my casual checks with these two lenses it seemed as though the DA14 was just a tad wider that the PTLens corrected fisheye. I will have to do some more experimenting with the DA14 and the Pentax 16mm fisheye to see what the real difference is.

The reason I ask is my (calculated) HFOV for the Zenitar is a
little wider than for a 14mm rectilinear, and a defished Zenitar
image has exactly the same HFOV as the fisheye original.

My calculations would indicate that the Zenitar or Pentax fisheye should yield a wider FOV diagonally than the DA14 as in this equation:
FOV (equisolid fisheye) = 4 * arcsin (frame size/(focal length * 4))
16mm fisheye = 104.82 degrees diagonal FOV
DA14mm = 90 degrees diagonal FOV

Once defished and cropped I cannot answer via calculation, but I can do a test.

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John Bean

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Lance B
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