[Dartmoor Dave]

A rectilinear 16mm on APS-C should give the same field of view as a 24mm on full frame. But my Zenitar 16mm on APS-C gives a field of view significantly wider than my 24mm on full frame and closer to my 20mm. I think of it as roughly equivalent to a 14mm rectilinear on APS-C.

The Zenitar defishes extremely well using the PT lens plugin, and I've often used mine as if it was effectively a rectilinear. But for astrophotography I expect defishing would produce a slight smearing effect on stars towards the corners, although it should work fine if you don't intend to defish.


Note: The quality of the results from defishing is very dependent on the software used for the job. The only plugin I've tried that really works for me is PT Lens.

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Last edited by Dartmoor Dave; 06-07-2019 at 12:38 AM.

[stevebrot]

You've done your arithmetic incorrectly. On your K-5ii, with it's APSC sensor, the 14mm will be a "21mm-equivalent" and the 16mm will be a "24mm-equivalent", assuming comparison to a full-frame 35mm camera.

This is true except that the fisheye has a much wider FOV (180° diagonal on 24x36mm FF) for its focal length than a rectilinear 16mm (~ 107° diagonal on FF). The 1.5 crop factor equivalence does not work well in this case.


Steve

[ZombieArmy]

The 14mm is great in my experience but I ended up returning mine because of decentering problems. I haven't heard of such issues with the Zenitar.