Fisheye: Let's get to know this special lens a little better

The fisheye is undoubtedly the most particular and "transgressive" photographic lens that exists, but also the most difficult to use and the most deceptive.

The fact that it offers a huge angle of view often misleads the photographer and leads him to use it incorrectly, resulting in abnormal and awkward photographs.

Not surreal and creative, but real visual "monsters". Let's find out its features, but above all how and where to use it to our advantage.

Observing the front lens of one of these lenses, rounded like the eye of a fish, you immediately understand the origin of the name.

Its peculiarity lies in being equipped with a huge angle of view compared to its colleagues: 180 degrees.

This means that if you are not careful you risk finding your own feet and the tip of the hat you are wearing in the frame!

Seriously, a 180 degree angle of view means that, if we place the camera on the ground and with the film plane parallel to the horizontal plane, it will be able to include everything around it starting from the horizon line in the frame.

On the one hand this is an advantage, but on the other it exposes you to several risks, such as seeing disturbing elements or bright flares appear in the frame.

Types of fisheye

There are two types of fisheye lenses on the market:

• rectangular
• circular

These denominations do not derive (obviously) from the shape of the lens itself, which is always cylindrical, but from that of the image they produce on the sensor (first on the film).

Outwardly, the circular fisheye is always devoid of a lens hood, for the obvious reason that it "sees" all around up to the edge.

The rectangular one is instead equipped with a lens hood, albeit very small, which proves to be invaluable in preventing the entry of stray light and therefore the generation of flare on the photo.

It should also be said that this type of lens is much less sensitive to the problem of stray light and internal reflections, so much so that you can photograph the sun without too much fear of seeing strange flashes appear.

focal length

The focal lengths of fisheyes vary between 16mm and 6mm ; the most common ones are 16mm and 15mm for rectangular ones, 8mm and 6mm for circular ones.

Usually this generates confusion, especially among beginners and amateur photographers who approach the curvilinear world of these fantastic lenses for the first time.

The confusion arises from the fact that we are used to thinking in focal lengths and with them we distinguish the types of lenses.

Therefore, a 50mm is a normal, below that we enter wide angles, then under 20mm in super wide angles, which also reach 14mm and even the legendary 13mm Nikon.

Some think that fisheyes are obtained only by going below this value and are therefore displaced by learning of the existence of 15mm and 16mm "fisheye".

The distinction, in fact, does not lie only in the width of the angle of view, but in the fact that the lines are curved and not kept straight as in wide-angle lenses.

Deformation and curvature of the image in fisheye

One of the typical and peculiar characteristics of this kind of lens is in fact that of curving the lines.

This is an extremely evident deformation, which strongly characterizes it and constitutes its true identity, in addition of course to the width of the field angle.

The difference compared to super wide angles, which have similar focal lengths, lies in the fact that in them the lines are kept straight.

Outwardly, the circular fisheye is always devoid of a lens hood, for the obvious reason that it "sees" all around up to the edge.

The rectangular one is instead equipped with a lens hood, albeit very small, which proves to be invaluable in preventing the entry of stray light and therefore the generation of flare on the photo.

It should also be said that this type of lens is much less sensitive to the problem of stray light and internal reflections, so much so that you can photograph the sun without too much fear of seeing strange flashes appear.

Do not think that the curvature is a defect or a limitation, just as the fact of keeping the lines straight represents an advantage or a value, because things are not exactly like this, quite the contrary.

Let's refer to the lesson on super wide angles for what concerns their strengths and weaknesses, and now let's focus on those of fisheye.

As we can see from the image, the only lines that remain perfectly straight in the frame are the vertical and the horizontal which form the central cross .

All the others tend to curve towards the extremes of the photo. The following photo is extremely clear to illustrate what has just been said.

It portrays a square mesh fence and this helps to clearly highlight how only the vertical and horizontal wires that pass through the central cross in the photo have remained linear and straight.

All the others tend to curve symmetrically (that is, in equal measure up and down, for the vertical ones; to the right and left, for the horizontal ones), arching more and more as they move away from the central cross .

How to manage curvature

This feature is, as we repeat, the crux of fisheye lenses and must be managed with great care to make the most of it and not be penalized.

In the lesson on "how and when to use fisheye lenses" we will see better in which type of photography they are indicated and where they should be avoided.

Never in architecture or portraiture, but…

Let's just say that, in principle, they are not recommended in all those cases in which there are evident and dominant lines in the shot, therefore in particular architecture and interiors, but also when people have to be portrayed, because the deformation is also evident on the faces .

On the contrary, they are suitable for landscapes and outdoor environments, without notes of lines, and to emphasize the circularity of structures, both natural and architectural.

The two photos that follow offer us two examples of when to avoid its use and when instead it is even ideal to use it.

The first shows a totally (and I would say horrendously) distorted view of Venice and its architecture; evident that this photo required a wide angle and not a fisheye.

The second concerns the Colosseum and instead shows how the curvature of the lines typical of this lens even enhances the circularity of the monument and emphasizes the depth of the shot, giving the reader the sensation of "falling into" the photo.