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Differences between the available fisheye lenses for the NX mount

Started Feb 11, 2015 | Questions thread
ocphotodad Regular Member • Posts: 116
Re: Differences between the available fisheye lenses for the NX mount
1

Jan Behrens wrote:

According to my knowledge, there are currently (at least) 4 different fisheye lenses available for the Samsung NX mount:

Note: According to my knowledge, the Samyang lenses are also sold under the brand names Bower, Rokinon, or Walimex.

They all seem to have a 180° diagonal angle of view. The original Samyang lens (which I also own) was occasionally praised for its nearly stereographic mapping [r=2*f*tan(phi/2)]. It's not completely stereographic though, since objects at the edge are slightly distorted (local distortion, which should be zero for a truly stereographic projection). I would assume that the real mapping function of the Samyang 8mm f/3.5 lens lies somewhere between a stereographic [r=2*f*tan(phi/2)] and an equidistant (linear) [r=f*phi] projection.

I assume that the Samyang 8mm T3.8 movie lens is optically equal to the Samyang 8mm f/3.5 lens, except that the aperture can be controlled continiously via the gear ring. Is this correct?

My second question is: What are the projections of the other fisheye lenses? Do they have a better projection (in the meaning of being stereographic), or a worse one? Is there somewhere a comparison chart? Does the Samsung fisheye lens have a projection that is close to being stereographic at all?

The f/3.5 and T3.8 fisheye lenses from Samyang seem much heavier than Samyang's f/2.8 fisheye lens. I assume this is because they were originally designed for camera systems with a longer flange focal distance. (The f/3.5 lens is also available for the Canon EF and Nikon F mount.) So my third question is: Has the heavier design of the f/3.5 lens any advantages or is it just a disadvantage due to design compatibility with systems that have a greater flange focal distance?

Regards
Jan Behrens

These questions are over my pay grade. But I found two sources that might help a little:

http://erphotoreview.com/wordpress/?p=4930

http://www.dpreview.com/forums/post/55127611

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