Ultrawide lens compared with fisheye

One of the early Micro Four Thirds lenses was the Lumix G 7-14mm f/4 ultra wide angle zoom lens (my review). In 35mm film camera equivalent terms, it goes as wide as 14mm (7mm times the crop factor of 2).

This is a very wide rectilinear lens, but not quite as wide as you can get with other formats. For Canon Fullframe cameras, you can get the amazing EF 11-24mm f/4, and for crop DSLR cameras, you can get the Sigma 8-16mm f/4.5-5.6, with a 12mm equivalent wide end.

The Lumix G 7-14mm used to be the most expensive M4/3 lens. It is no longer, due to other more expensive lenses, but it is still the widest rectilinear zoom lens. But how does it compare with a fisheye lens, in terms of field of view? Here are some example images for comparison (click for larger images):

Lumix G 7-14mm f/4 @ 7mm	Samyang 7.5mm f/3.5

The fisheye image (right above) can be defished (click to see how it can be done using the free software Hugin). Defishing yields this result:

Samyang 7.5mm defished	Samyang 7.5mm desfished and cropped

When defishing using a rectilinear projection, like I did above, the image gets very stretched in the corners. To avoid this effect, some use the Panini projection in Hugin.

Comparing the two fields of view shows that you get a lot wider images using the fisheye lens:

As you can see, the fisheye lens gives you much wider images, but keep in mind that the corners are quite stretched, and you may not be able to use the whole picture when defishing. Still, even if you crop it a bit, it is way wider than what you get from the Lumix G 7-14mm f/4 ultra wide angle zoom lens.

Other lenses

Another very wide rectilinear zoom lens is the Olympus 7-14mm f/2.8 PRO. It is similar to the Lumix G 7-14mm f/4 in terms of field of view, but adds another stop of aperture, at the expense of a larger, heavier lens, and a steeper price tag. You shouldn't expect better images from this lens, but you get the possibility to use f/2.8. Also, the lens is weather protected, meaning that it is more likely to survive some water splashes.

The Samyang 7.5mm f/3.5 that I used above is a manual focus lens. There are also two autofocus capable fisheye lenses:

The Lumix G 8mm f/3.5 is one of the smallest autofocus capable fisheye lenses, but not any better optically than the Samyang lens, see a comparison here. The lens is still very good, but a tad expensive.

Olympus also has a fisheye lens, with a record large f/1.8 maximum aperture, the Olympus 8mm f/1.8 PRO. This large aperture is rarely needed for real life use, in my opinion. However, people who are interested in astrophotography will find it interesting. Also, it is good for use underwater, inside a waterproof housing.

Lens	Lumix G 7-14mm f/4	Samyang 7.5mm f/3.5	Olympus 7-14mm f/2.8	Lumix G 8mm f/3.5	Olympus 8mm f/1.8
Weight	300g	179g	534g	165g	314g
Length	83mm	48mm	106mm	52mm	80mm
Diameter	70mm	60mm	79mm	61mm	62mm
Lens elements/groups	16/12	9/7	14/11	10/9	17/15
Pros	Small, light, not too expensive these days	Very good image quality, fantastic value for money	Fast aperture, weather protected	Compact, good image quality	Very fast for a fisheye, weather protected
Cons	Sharpness could be better at 7mm f/4, but improves when stopping down. Some purple flare	No autofocus	Large, expensive	Somewhat expensive	Do you really need a so fast fisheye?