Zooming and Reduction of Field of View has several consequences on the aesthetics of the photos. One must know these consequences for better photography. We elaborately wrote about Zoom Lens and Field of View. Unfortunately, there is another variable that can significantly add up as variable in zooming and reduction of field of view – Image Sensor Size and Field of View. Actually, the topic Zooming and Reduction of Field of View utilizes more the core concepts of Optics. We will obviously avoid the mathematical formulas as practically our need is the result.
Zooming and Reduction of Field of View : A little theory
We have already seen what the effects of focal length has on the perspective and the depth of field (i.e. blurring). In this article we will see how focal lengths can affect on the angle of view. In layman’s terms zoom affects the amount of things that we include in the picture, especially the background.
To understand what the field of view, think of how the human eye works. If you look straight in front of you, you can see all the things that are in an area (which we call the visual field) with a specified extension. When you see something that is outside of the area, to the right or left, you have to rotate the head. Do not calculate the fact that we can move our eyeballs.
This area form a cone that extends away from the eyes, so it is measured in degrees. The horizontal field of view (what is considered usually) of a single human eye is between 43° and 45°. The angle of the field of photographic objectives varies depending on the focal length. There are tables available to compare how the angle of view varies with the focal length. Please note that these are the valid values ??for film SLR camera and 35mm full-frame digital SLR cameras. If you want to relate them to your camera you must know the crop factor and then calculate the equivalent focal length.
What will interest you the most is the horizontal field of view. When we are using wide angle lens, the field angle is wider than that of a human eye. The lengths in case of tele, from 70mm up, has a field angle smaller than a human.
Zooming and Reduction of Field of View : Tests
In fact, you can do these tests :
- If you have a compact or bridge camera, minimize the zoom, if you set it to a lengths below 35mm, watching the scene in front of you with your eyes, with one eye will be even more evident, you are viewing the same scene through the camera. You will notice that the view of the camera is larger than the one you perceive with your eyes.
- If you try to contrast with a telephoto lens, you will see how things get tight. To make it even more scientific evidence, do this: framing a subject with wide-angle, you notice the width of the visual field, or a “how things are” in the frame, look the same subject with the naked eye and back until it becomes about the same size as opposed to when you were framing with the camera, Now observe how wide the field of view, you will see that things are including many thing less. Now read on, to see with your own eyes how the changes in angle of view change a photo.
Now watch this infographic :
Actually, it is not only the angle of view but the wavelength of incident light also matters :
FOVmin = rBWmin / ?Gmax
As we do not have such wide range of ‘viewing capability’ it is not mathematically expressed. Again, with the same focal length, the size of opening will also affect the Field of View.