Field of view (FOV) is a term used for masks that refers to the visual range that the user experiences when wearing the mask. This range can be horizontal as well as vertical. There are groups that evaluate field of view but they do it in relationship to scuba diving rather than snorkeling and while the sports are different from one another, the field of vision principle is the same. Quality manufacturers do take the field of view into consideration when they design their products and the parts can have the greatest effect on the field of view include the viewing lens, the frame and the skirt.
In looking at the viewing lens, one will notice that masks may be constructed with a single viewing lens or multiple lens configurations. The most common positioning with multiple lenses would either be one or two lenses in the front of the mask with two additional windows on the sides. (There are rare exceptions and having more than four lenses but again that is rare.) The purpose of the multiple lenses is to increase the field of view more horizontally than vertically. The designs with side windows that are set perpendicular to the front windows do allow for an increase in peripheral vision but do not really increase the field of view of the front windows. This is because the windows separated from the from front is by a the frame. There are designs that have windows that are angled rather than perpendicular to the front lenses and this styling is where the lenses are chemically bonded to the front lens itself creating a truer panoramic view. This style does increase the horizontal field of view significantly as well as giving better peripheral vision. The shape of the lenses are also a factor with regard to field of view. Lenses that are vertically longer in length will increase field of view vertically while wider length lenses will increase it horizontally. To read more about mask lenses, click here.
The frame of a mask can also have an affect on the field of view, ones with thicker frames may inhibit the field of view and may be less than a mask with a thinner frame. It should be noted that there are styles that have no frame at all and these are designed to have the lenses attached directly to the skirt.
The skirt has both a direct relationship to the field of view and a relationship that can be considered illusionary. If the skirt places the viewing lens farther away from the eyes, then the field of view may be decreased and this is the direct relationship. The illusionary relationship is with regard the skirt being made using clear silicone or black silicone. The clear silicone allows for more light to enter the internal viewing area giving the sense of openness. The black silicone can produce an effect that is referred to as "tunnel vision". This would give the user a feeling similar to standing in a tunnel and looking out the entrance. This feeling can cause a closed in feeling to one who may have a touch of claustrophobia. More on skirts, watch our video to the right.
As was stated previously, the manufacturers do take field of view into consideration when designing their masks. The descriptions of field of view should be considered general rather than definitive descriptions. To compare field of view when trying on different mask styles, the user should stand in one spot and fix their eyes forward at a predetermined object such as a picture on a wall. The user should take note as to how much space they can see to both the right and the left side of the chosen object. They should also take note of how much viewable space there is both above and below the object as well. One should remember that fit and comfort will take precedence in this process so mask to be compared should be checked for fit and comfort first.