Field of view (FOV)

Field of view (FOV)

In photography, the angle of view (angle?of?view) is the angle range at which the camera can receive images in a general environment, and it can also often is called the field of view. The angle of view is different from the imaging range. It describes the image angle that the lens can capture. Generally speaking, the imaging circle of the lens is large enough to cover the film or sensor ( There may be a little edge vignetting). If the imaging range of the lens cannot cover the entire photosensitive element, the imaging circle will be visible, usually accompanied by severe edge vignetting. In this state, the viewing angle will be limited by the imaging range.

Field of view in English: field angle; The relationship between focal length is as follows:?

h?=?f*tan\[Theta]?

Image height?=?EFL*tan?(half FOV)?

EFL is the focal length?

FOV is the field of view

Contents

1 Definition:

2 Category:?

p>

3 Classification of lenses according to field of view

4 Field of view (FOV) of a camera

Definition:

1. In optics In the instrument, with the lens of the optical instrument as the vertex and the angle formed by the two edges of the maximum range through which the object image of the measured target can pass through the lens, it is called the field of view angle. As shown in Figure 1. The size of the field of view determines the field of view of the optical instrument. The larger the field of view, the larger the field of view and the smaller the optical magnification. In layman's terms, if the target object exceeds this angle, it will not be included in the lens. ?

Figure 1

2.? In the display system, the field of view angle is the angle between the edge of the display and the line connecting the observation point (eye). For example, in Figure 2, the AOB angle is the horizontal field of view, and the BOC is the vertical field of view.

Category:?

The field of view is divided into object side field of view and image side field of view. Generally, users of optical equipment are concerned about the object field of view. For most optical instruments, the measurement of the field of view is calculated based on the diameter of the imaged object as the field of view. Such as: telescope, microscope, etc. For optical equipment such as cameras and video cameras, since the photosensitive surface is rectangular, the field of view is often calculated based on the diameter of the imaged object at the diagonal of the rectangular photosensitive surface, as shown in Figure 1 left. There are also ways to calculate the field of view based on the length of the long side of the rectangle, as shown in Figure 1 on the right. The calculation method can be seen in Figure 1. You can also use metric methods to obtain the field of view angle parameters. Wide-angle parallel light tubes are generally used for measurement. Because they resemble a funnel, they are commonly known as: funnel meters. The measurement method is shown in Figure 2. At one end of the lens under test, check the scale on the glass plane at the bottom of the wide-angle collimator and read the angle value. The maximum scale value is the field of view of the optical instrument under test. The lens under test may have different focal lengths, resulting in the scale not being visible to the naked eye. A convex lens with appropriate focal length can be added as an auxiliary lens to view the measurement results. When measuring, the lens under test should be moved back and forth along the optical axis until the observed angle is the largest, which is the field of view of the lens under test. The measurement method of the camera is the same as above. When measuring the camera, you can check the viewfinder window. Because the resolution of the LCD screen of the digital camera is low, you can check the photos taken by the camera. The relationship between field of view and focal length: Generally speaking, the larger the field of view, the shorter the focal length. Here are a few examples: The field of view of a long focal length lens is narrower than 40°. For example, the focal length of the lens is 2.5mm and the field of view is about 45°. The focal length of the lens is 5.0mm, and the field of view is about 23°. The focal length of the lens is 7.5 mm, and the field of view is about 14°. The focal length of the lens is 10?mm, and the field of view is about ?12°. The focal length of the lens is 15mm, and the field of view is about 8°.

Lenses are classified according to the field of view:

Standard lens: The field of view is about 45 degrees, and it has a wide range of use. ?

Telephoto lens: The viewing angle is within 40 degrees, which can be used to shoot at long distances. ?

Wide-angle lens: Angle of view above 60 degrees, large observation range, near-image distortion

Viewing angle (FOV) of one camera

FOV-5

For images of distant objects produced by rectilinear projection lenses (without spatial distortion), the effective focal length and image format size are sufficient to define the viewing angle. ?Computing nonlinear images is relatively complex and not very useful in most practical applications. (In the case of distorted lenses, such as fisheye lenses, a long lens with distortion can have a wider angle of view than a shorter lens with lower distortion) [1]? The angle of view may be horizontal (from the left end of the image to the right end) , calculated vertically (from the top to the bottom of the image) or obliquely (from one corner of the image to the opposite corner). For rectilinear projection images, the angle of view (α) can be calculated from the selected size (d) and the effective focal length (f) as follows:

α=2arctan(d/2f)

< p > d represents the calculation of the size of the film (or photosensitive element) and one direction.

For example, for a 36mm wide film, d=36 mm can be used to obtain a horizontal viewing angle. ?Since this is a trigonometric equation, the angle of view does not have a linear relationship with focal length. However, except for wide-angle lenses, it is reasonable to approximate α≈d/f radians or (180d/pi *f) angle.

The effective focal length approaches the stated lens focal length (F), except for micro The distance from the photographic lens to the subject is close to the focal length. In this case, the magnification (m) must be taken into account

f=F*(1+m)

(In photography m? is usually defined as a positive value , albeit an inverted image.) For example, at a magnification of 1:2, we find that f=1.5F and the angle of view is reduced compared to one with the same focal length for distant objects. 33%.

Another influencing factor in macro photography is lens asymmetry (lens asymmetry refers to the fact that the aperture of the lens looks different from the front to the back). Lens asymmetry will cause distortion. Surface (nodal?plane) and?pupil?positions. ?The?effect?can?be?quantified?using?the?ratio?(P)?between?apparent?exit?pupil?diameter?and?entrance?pupil?diameter.?The?full?formula?for?angle? of?view?now?becomes

α=2arctan(d/(2f(1+m/p))

For viewing angles, you can also use FOV tables. Or paper, or lens calculation software to find it.

Example[edit] Suppose a 35mm camera is equipped with a lens with a focal length of ?F=?50mm.

The image specifications of a 35mm camera are 24mm (vertical) × 36mm (horizontal), and the diagonal distance is approximately 43.3mm. When focusing at infinity, f=F, and the angle of view is:

FOV-4