View Full Version : trying to understand offset for 8mm fisheyes
03-25-2011, 07:36 PM
Why would I tilt up or down a sigma 8mm fisheye (used on a Canon 5d)
03-25-2011, 07:57 PM
I tilt up so I can have overlap at the zenith. 5 degrees of positive tilt gives 10 degrees of overlap across the top of the sphere. No need to shoot a Zenith shot. With this tilt, I get the monopod head in the shot at the Nadir. The Nadir is so very small and easy to patch.
My understanding of a downward tilt is for ease of stitching. This requires a Zenith shot.
Both require a hand held Nadir shot if you want to complete the sphere.
03-26-2011, 09:40 AM
as Dennis pointed out, 5 deg up will close the zenith with ample overlap. so no zenith shot is needed. Some experienced users prefer 2.5 deg up to get sharp image around nadir. That is why I make 2.5 deg option for R10. It is not available in R1 though.
when you shoot pole panos, you may want to use -2.5/-7.5 tilt and move the lens 10-15mm in front usual NPP value. This reduces the nadir hole and give sharper image arund it. Patching a nadir of pole pano is much more difficult than the zenith which is usually just the sky.
03-26-2011, 11:12 AM
I never thought about down tilt in order to help the Nadir become sharper.
I usually have to blurr the Nadir patch shot a bit so it matches the lower edges of the other images. Not always, but often enough.
If tilting down provides good enough results, taking a Zenith shot would be worth it if the overall panorama is sharper and not much more difficult to process. Zenith and Nadir shots are usually static. Even in crowd shots with moving people, chances of having someone moving in the Zenith shot is unlikely.
Time to learn a new shooting technique.
03-26-2011, 12:12 PM
I think I will have to take "add ons" to my lens comparison test shots. Add +2.5° and -2.5/-7.5° tilt and add 10-15mm off Nadir pole shots.
@Bill, if you like to test it, I add the link to my D700 Sigma 8mm/f3.5 test shots.
Workflow: 0°, +5° and +7.5° to check the Zenith Nadir holes with R1/R10, 2x +60° 180° visa versa to test horizontal connection in case of impossible Zenith at +90°, +90°, 2x -90°Nadir with Nadir Adapter.
For Nikon users:
Orange dots are laser placed in vertical and horizontal to set up a template in PTGuiPro by spreading CP to the outer circle of the lens in vertical and horizontal direction. You could make a template with this set of pics, adapt it to your project and "fine tune" it with a project shot with your equipment. © 2011 firstname.lastname@example.org
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