panomano
Posts: 5
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Registered: 31 Jul 2010
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Pano images and lens - Help!
Posted: 31 Jul 2010 at 3:22 GMT
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I have a Canon eos rebel xt (8 mp). I have a rokinon 8mm fish eye lens (asperical - full frame). The lens specs says 180 degress diagonal. I use autodesk stitcher. Shooting in a vertical/portrait position it appears I am only getting about 150 degress.
Do I have the wrong lens to capture 180 degrees? Very frustrated. help please.
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No One
Posts: 495
Location: Sri Lanka
Registered: 14 May 2004
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 4:03 GMT
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Lens and camera sensor size matter. This combo will not get you 180 degrees of vertical capture in one image. Do you have the wrong lens or camera? Both. 
Right lens, shaved, on a full frame camera, wrong lens on a aps sensor camera (xt).
Just look through the lens, do you see your feet and the point directly above you? If you did then you would have 180 degrees vertical, you don't.
But all is not lost, with this setup you need 6 around, and one up/down for a complete 360 by 180. That works, try it.
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panomano
Posts: 5
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Registered: 31 Jul 2010
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 4:58 GMT
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What would be the right lens for this camera? What does "right lens, shaved" mean?
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No One
Posts: 495
Location: Sri Lanka
Registered: 14 May 2004
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 5:22 GMT
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replace the camera, get a used 5D or other full frame camera, 5D II or 1Ds.
replace the lens, get a sigma 4.5mm
shaved means you've cut off the lens hood so the full FOV of the lens can be used by a full frame sensor.
if all of this means nothing to you, you need to go back and read up on basic DSLR camera systems.
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Hans Nyberg
Posts: 2760
Location: Denmark
Registered: 28 Aug 2005
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 6:08 GMT
updated: 31 Jul 2010 at 6:09 GMT
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panomano said: I have a Canon eos rebel xt (8 mp). I have a rokinon 8mm fish eye lens (asperical - full frame). The lens specs says 180 degress diagonal. I use autodesk stitcher. Shooting in a vertical/portrait position it appears I am only getting about 150 degress.
Do I have the wrong lens to capture 180 degrees? Very frustrated. help please.
The Rokinon 8mm is a perfect lens for your camera.
You can do a full spherical with 4-6 around + zenith and nadir.
If you want to do it with just 4 around you need a Sigma 8mm however remember that many people also uses the Sigma 8mm with 4 around + zenith because this gives you better quality and easier stitching.
Another good lens is the Tokina 10-17 mm wich needs 6 around + zenith and nadir.
And of course you can do full spherical with any lens, you just need to take more images.
It is all about what quality you want and as you just have 8mp I would start with the Rokinon which gives you a little more resolution than the very expensive Sigma 8mm.
The Rokinon is a special kind of fisheye which is not compressed at the edges like other fisheyes so it will give better quality all over your panorama. You stitcher will optimize it as a 10mm not as an 8mm.
And of course you need a panohead suitable for it.
Hans
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John Houghton
Posts: 3412
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 6:35 GMT
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The Rokinon 8mm lens has a diagonal fov of 166° on your camera. The horizontal fov in portrait orientation is 98° and vertical fov is 166°. There is just enough overlap to enable a full 360x180 panorama to be made with 4 shots around + zenith + nadir.
If you need a full vertical fov of 180 degrees, then you can use the Sigma 4.5mm fisheye. That gives a full circle image on the APS-C sensor. The disadvantage is that you waste a lot of pixels in the blank areas of the image frame. The result is that the maximum size of a 360x180 degree equirectangular image that can be generated is about 3900x1950. The Rokinon can generate a 8400x4200 panorama, so the quality is much better. (You need 6000x3000 for a good quality fullscreen panorama). Another alternative is the Sunex 5.6mm fisheye.
John
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enbilaman
Posts: 119
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Registered: 3 Mar 2006
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 9:58 GMT
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John,
I guess you didn't want to give the same value for vertical fov and diagonal fov. The vertical fov might be actually about 162 deg.
I think that there is another alternative to get a full 360x180 panorama without zenith and nadir shot: couldn't an old Sigma 8 mm f4 fisheye lens be advisable also to be used on a Canon with a APS-c sensor?
Many of us have been happily using such a combo for quite a long time before this lens become superseded by the newer f3.5 model.
Of course one has to take care of some flare vulnerability and the softness of that venerable lens needs to be mitigated by stopping it down enough, but from my own comparison tests and measurement, it is IMHO on par or better than the Sigma 4.5 mm or the Sunex 5.6 mm for producing 4-shot panoramas. While the image is not fully circular, it is cropped only along two sides on the small sensor and offers 180 deg VFOV in portrait mode.
There are still some brand new Sigma f4 that are sold on internet and second hand units can be easily found for sale.
Michel
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mediavets
Posts: 1948
Location: Isleham, Cambs., United Kingdom
Registered: 8 Feb 2008
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 10:29 GMT
updated: 31 Jul 2010 at 10:30 GMT
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panomano said: I have a Canon eos rebel xt (8 mp). I have a rokinon 8mm fish eye lens (asperical - full frame). The lens specs says 180 degress diagonal. I use autodesk stitcher. Shooting in a vertical/portrait position it appears I am only getting about 150 degress.
Do I have the wrong lens to capture 180 degrees? Very frustrated. help please.
You should be getting approx. 167 degrees FOV on the diagonal with a Canon 1.6x crop sensor. You would get 180 degress FOV on the diagonal with a Nikon 1.5x crop sensor.
No, you don't have the wrong lens, as others have explained you just need to adopt the appropriate shooting pattern to obtain 360x180 coverage.
Andrew.
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John Houghton
Posts: 3412
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 11:27 GMT
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enbilaman said: I guess you didn't want to give the same value for vertical fov and diagonal fov. The vertical fov might be actually about 162 deg.
Thanks, Michel. Sorry about the typo. I intended to say 143° vfov in portrait orientation.
John
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Doug Aurand
Posts: 3282
Location: Albuquerque, NM, United States
Registered: 2 Jan 2008
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 14:40 GMT
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panomano
If a lens can be used on cameras with both Full Frame Sensors and Cropped Sensors like your Canon, the specs are usually for a Full Frame Sensor.
The Sigma 8mm is described in their website as a "Circular Fisheye" but only produces a curcular image on a Full Frame Sensor. Its a Cropped Circle on a Cropped Sensor like your and mine.
Hope that helps
Doug Aurand
Albuquerque, NM
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panomano
Posts: 5
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Registered: 31 Jul 2010
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Re: Pano images and lens - Help!
Posted: 31 Jul 2010 at 21:20 GMT
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Great advise and insight thank you all.
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