Angle of View in Photography referred to that angle in the given object space which is limited by the edges of the recording format. It is field of view for a camera. To denote Angle of View in Photography, some people interchangeably uses with field of view. But, field of view is for living creatures, not machines. As human and other living creature’s vision is very complex, field of view can not be directly measured but indirectly calculated. When a technical instrument’s field of view is described, it is said in reference to human vision. That is why we said Angle of View is actually the Field of View of a Camera.
Basics of Angle of View in Photography
The Camera records on a Flat surface, be it a Digital Sensor or Film. Although there are cameras with concave recording surface, but those are not in common use. Take the situation, a nice looking solitary flower is on a normal background. As nothing is actually flat, has some depth and concavities, our eye’s retina is designed to capture it rightly. That is one of the reason why we can see more than a camera can see. Additionally the “post processing” of the image from both eyes are done inside the brain, sometimes we do not need to get the actual presence of something to “see it”. That is why we see peoples are showing various images that can confuse at one look.
A camera’s Lens is a part of a sphere. From this basic of optics, we calculate Angle of View. This is the actual equation for Angle of View :
α is the Angle of View, d is the size of sensor, f is the focal length of the particular lens. If we use 36 mm sensor, that means a full frame sensor, then the calculation of Angle of View in Photography becomes easier to some extent. But in practical life we need Angle of View for all possible combinations.
Usage of Angle of View in Photography
From the formula, the angle of maximum Angle of View in Photography for normal lenses is limited to -90 ° and +90 °, fish-eye lenses have some what more than 180 ° Angle of View. We need this Angle of View in Photography to get the Field of View (FOV). FOV needs not to be calculated from Angle of View, there are Tables and Softwares available.
More on Angle of View
Angle of View is quite wide in case of human eyes. Just like Fish Eye Lens, we do “feel” a peculiar rounded edges. We always “see” optically more rounded to get a more wide Angle of View, definitely that is lessened by concave retina and binocular vision but most importantly our brain corrects it. You will always see at distance as if the Sky is becoming like the inside of a dome and it is meeting with the rounded edge of the land at far. You never see a traffic light in the way a Fish Eye Lens reproduces, but distant sky becomes somewhat like that. This happens partially because of limitation of our eye’s optics to compensate the side effect to increase the Angle of View directly but more due to God’s naughty smile by not programing our brain to look far away by correcting it rightly ! Pathologically, in some diseases, this Angle of View of human eyes becomes smaller and the patent actually describes his / her sight to be somewhat like a Fish Eye Lens takes the photograph. Even if the Lens and Retina is stopped to get worsened or rather steps taken to keep or revert the optical system of eye to normal, the Angle of View unfortunately remains lower as we can not correct the brain somehow which was trying to compensate to retain the Angle of View.