I just did my very first spherical panorama today with PTGui then put it into a program called KRPano and I'm really happy with the results. I can see myself doing more of this type of thing but I wonder if I should get a fish eye as several You Tube tutorials show people using them.
In the tutorials I see people getting a full 360 degree panorama in 4 shots a full spherical takes 7. I just did my pano today with a 16-35mm lens but I needed 8 shots to get 360 degrees and to make a big overlap I shot three rows plus the Zenith and Nadir shots making a total of 26.
I have a full frame sensor, so if I bought say the Canon 8-15mm zoom I would have to set it at 15mm.
I have to wonder how can this extra 1mm make so much difference ?
It's not just the focal length, but more due to the different projection (rectilinear versus fisheye) that does the trick.
The EF 8-15mm lens is super, but the 15mm is no slouch either. If money is not an issue, I'd get the 8-15 in a heartbeat, it's very sharp all the way up to the edges. It's coating is quite good which is important because it's hard to keep lightsources/the sun out of the image. The only drawback is that manual focusing (for hyperfocal DOF) is tricky because of the short focusring throw angle.
When you need to minimize the number of shots, e.g. for speed of shooting a 360 VR panorama in an awkward spot or with lots of movement, it can be done with a 15mm fisheye in 5 shots (+ one for the nadir if the ground detail cannot be reconstructed). You'd shoot 4 shots aiming down 20 degrees below horizontal, and one straight up for the zenith. So in a maximum of 5-6 shots you can move to the next spot.
When shooting in contrasty lighting conditions is is not too much of a burden to add exposure brackets.