HDRI Community

autofocus is undesirable for shooting 360° panoramas which should always be shot with manual focus, typically at infinity, focusing per individual shot will likely cause stitching errors

samyang, rokinon and bower are all the same lens, get the newer version with removable lens hood and it is fine on full frame cameras

http://www.bhphotovideo.com/c/product/886556-REG/Rokinon_hd8m_c_8mm_f_3_5_HD_Fis...

sam

Well with the samyang lens, as Sam has mentioned, the newer ones have a removable hood, so you wouldn't need to shave it off.  If you're getting another lens without a removable hood with at least 8mm or less (10mm won't give you much more fov, but looks better since you don't have the hood in the image), then you can. I'm not sure if I would recommend doing it yourself, since obviously, there is some risk involved, but you can find tutorials on youtube. 

As far as autofocus goes, its not really needed much for wider angle lenses, like it is for longer focal lengths, especially telephoto lenses.  Especially if you have a higher aperture, changing the focus won't really change much.  I always keep my lens on manual focus, and keep it at infinity.  Having autofocus lenses are nice though, for reading exif with the aperture and focal length.  The newer rokinon lens, I believe does have a chip for reading those values.

Well I never tried the sigma, I used to have the version 1 samyang, but sold it to buy a tokina 10-17.  Compared to the samyang, the tokina seems overall better in quality, but I mainly like it because the chromatic aberrations, vignetting, and lens flares are improved a lot.  As far as the sigma, from what I've read, its not that much better, especially the aberrations at the edges, but that's what you can expect from really wide angle fisheyes, especially with the 4.5mm sigma.

Well if you wanted a full image circle, I believe you need a full frame fisheye lens. I'm not sure which one you got, but from the rokinon description, it says its designed for cameras with APS-C image sensors. But it also says its compatible with full frame cameras. So yeah, I think you would have to get something like the sigma 8mm circular fisheye - http://www.amazon.com/Sigma-Circular-Fisheye-Canon-Cameras/dp/B000GE9SBM/ref=sr_...

You can buy the sigma, but remember, both will get the job done, and you have to decide if its worth more money, to be able to have the whole circle.  Unless you are using the lens for something else, the final result will be the panorama, so its not a big deal if you can't visually see the whole circle.  Also, I don't think you'll save on shots with the circle, since you'll still probably need an up and down shot.  I think you'd need the sigma 4.5mm to be able to shoot three images and cover the whole panorama. 

Also you have to consider the final output quality, and weigh speed (how many shots it takes) vs. quality (the final resolution of the panorama).  The more fov you fit into each shot, the less pixels you have to form your panorama.  So you have to decide what you're using the panoramas for, i.e IBLs, reflections, interactive tours, or print work.  That's why I personally decided to get a zoom fisheye, so I'm more flexible with what I can do with it.

Having said all of this, I don't want to tell you what you should buy, you have to decide what you want out of the lens and weigh its pros and cons.

Yeah I figured you might end up needing an extra shot horizontally, than with a fully circular lens in portrait. You mainly need a down shot or two to mask out the tripod.  Depending on what kind of tripod head you have that's not a big deal.  I have a nodal ninja with the nadir adapter, but if you have a head that only rotates horizontally, then you need to take the down shot handheld or rig something up. 

You also have to consider that having more images with more overlap gives you better quality overall, since you don't have to interpolate and grab as much information from the edges of your image, where your image is softer and any chromatic aberrations are the most extreme.  That's why when I had the samyang on my cropped canon 500d, I took 4 horizontal + 1 up + 3 down, for masking.  I eventually decided to take 6 horizontally for even better quality, which didn't slow down the process that much.

Overall, I would say that the samyang is a good starter lens, so I think you made a good decision. Its a good competitor to more expensive lenses, especially since its being updated once in a while.  It'd be interesting to see what they would improve on, in a third version.  You can always sell the lens later on, and put the money towards a better lens.  I got over $100 for the first version at a local camera shop.  If you do end up going with a sigma later on, I would probably go with the 8-16mm, since it gives you more flexibility and I think its only $50 more than the 8mm. Who knows, maybe in the future, sigma will make a 4-16mm fisheye, which would be crazy.