Originally posted by RioRico Great thread! But before I leaf thru all 19 (at this moment) pages, the following leads to a question:
The question is: if by Fisheye we mean a 180-degree FOV, filling the frame (like the Zenitar on a FF cam or the DA 10-17 on HF), then what's the label for a lens that puts a full circular image on the frame? Is it a FullFishEye? The first image in that thread is an 8mm lens on a K20D and it's NOT a full circle - I think 5-6mm is required for FullFishing.
not quite: by fisheye we mean fisheye (spherical projection, instead of linear, as mentioned above). it so happens that it is virtually impossible to get 180 - even "just" diagonal - fov with a linear projection (mostly due to physics, or one might say even due to geometry). this is why the concept of fisheye is often associated with 180. both the zenitar and the peleng (the 8mm you mentioned, i guess) are designed for a normal 35mm film frame. this means they are cropped on the aps-c sensors, so the peleng will not look like a "circular fisheye" anymore on the aps-c, and the zenitar will no longer be a 180 diagonal (so called full frame fisheye, because it fills the entire frame), the zenitar on aps-c becomes "merely" a very wide prime lens, with a (easily correctable, because it is not really distorsion, but honest spherical projection) fishyness to it, very compact, very well built (especially for the price), and pretty damn sharp i think, too. this is what i use it for (ultrawide on the cheap), sometimes i need to "correct" the sphericity, sometimes it works well for the shot and i leave it alone, other times it is impossible to notice it unless you've been there. to be very honest, the choice between linear and fisheye is choosing between two distorted renderings (linear is only perceived as more natural by most, but it is strictly not, and sometimes it is even
perceived as very wrong), the moral of the story being, i guess: when you go ultrawide, you have to somehow project a noticeably spherical reality on a plane rendering, so no matter what you do, it will not be "right" (for a very known and easy to relate to example, think of map projections, any plane map of the earth in any projection you wish to choose will be distorted and wrong in one way or another, that's because the earth is "round", and the map is flat, and there's nothing you can do about it really)
hope this helps shed some light