On Wednesday, 28 November 2012 at 17:18:57 +0100, Felix Hagemann wrote: > On 28 November 2012 12:10, Carlos Eduardo G. Carvalho (Cartola) > <[email protected]> wrote: >> Going back to your specific example, I don't think 9mm will have a >> much narrow angle than an 8mm lens. Do you have their fov to >> compare?
Partially. The 9 mm has: Horizontal FOV: 87.73° Diagonal FOV: 100.49° Vertical FOV: 71.68° I don't have a formula for fisheyes, so I can't give the output of my program, but I'm told that it has 180° on the diagonal. Being a fisheye, this *should* mean (on a 4:3 aspect ratio) a horizontal FOV of 144° and a vertical FOV of 108°. That's a long way from the 9 mm. >> Probably you will use the same number of images to stitch and will >> have almost the same final image size. > Having shot myself in the past with a 10mm rectilinear lens (Sigma > 10-20mm) and a 10mm fisheye (Tokina 10-17mm) I can tell you that the > difference in hfov is very noticeable. It's basically the difference > between 2 rows of 8 shots, nadir, zenith (so 18 shots total) and 6 > shots around, nadir, zenith (maybe two, I don't remember right now) > so 8 oder 9 shots in total. Yes, this matches my experience and expectations. I currently take 8 shots per row with the camera mounted vertically, and 2½ rows (the top row touching the zenith at 90° intervals), for a total of 20 images. I do it this way because of issues stitching with only a single zenith image. Reading Reinhard Wagner's "Profibuch HDR-Fotografie" (sorry, only in German), which refers to exactly this fisheye lens, he suggests 60° intervals and one row, which sounds pretty much like what you're doing. > You can actually enter the numbers in hugin to get an estimate. > Assuming crop factor 2 9 mm rectilinear yields 90° hfov while 8 mm > circular fisheye yields about 130° hfov. Where do you find that? I've tried this in the "Camera and Lens" tab with a photo taken vertically with the 9 mm lens. If I select "Rectilinear" it tells me 71.5° vertically, which presumably ignores the fact that it's mounted vertically, and doesn't say anything about HFOV. That tallies relatively well with my program above. But when I select "circular fisheye" it comes up with (only) 92.8°. That's some way from my estimate of 108°. Is there some other place you can get similar results? I also get the same results whether I select "full frame fisheye" or "circular fisheye". What's the difference? In any case, I can't see any mathematical correspondence between the focal length and the angle of view for fisheyes. Can anybody point me at some background information? > Back to the original question: > For me the step from a wide angle rectilinear to a fisheye was very > well worth doing. The noticable but bearable quality difference is > outweighted by the much easier stitching with the lower number of > shots, especially so for 360x180s. That's interesting. I've asked on the German Olympus forum and got a reply from Reinhard Wagner (the author mentioned above) that confirmed my suspicion that the distortion would be less, since a 360x180° panorama is a form of fisheye image anyway, and the image needs to be distorted less. If you're interested, the thread is at http://oly-e.de/forum/e.e-system/135036.htm Greg -- Sent from my desktop computer. Finger [email protected] for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft MUA reports problems, please read http://tinyurl.com/broken-mua
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