زوايا رؤية العدسات lens angles .. كتاب المرشد العملي

(Explanation of tables from 88 to 100)

LENS ANGLES ANGLES OF VIEW

The photographic lens records what lies in front of it within the limits of a specific angle, which we know as the angle of the lens.
vice versa .

These tables are of great importance to all those whose workers are involved in the initial planning for the production of the film prior to the start of shooting it, such as directors, screenwriters, set designers, those in charge of calculating production costs, etc., in addition to that. To its importance - no doubt to the photographers. Based on our knowledge of the data received about each of the horizontal and vertical angles that the school records with a specific camera, it can be decided in advance all the positions and places in which the camera can be placed to photograph a specific scene, whether it is on paper in the initial planning of the shots, or it is in a place Photography . Also, these tables are important when you want to compare the angles of view of the different lenses used in the different methods of displaying on the Wide Screen Systems. The angle of view of the lens depends on the following factors:

First: the focal length of the lens: the angle of view narrows the longer the focal length.

Second: Camera aperture: The rectangular aperture that is located behind the lens in the cinematographic camera, in front of which the film passes. This aperture exposes the flag, and the length and width of the aperture varies according to the size of the camera (for example, 16 mm or 35 mm) as well. The ratio of the aperture’s width to its length varies according to the shooting method, whether the film is 35. For those who speak, sound film, or a 35-millimeter silent film, or a 35-millimeter film prepared for disease on the wide screen. It is evident that the size of the image frame, that is, the size of the frame recorded on the film, corresponds to the size of the window of the cinematographic camera.


And in the 35 mm silent films, the image occupies the maximum space located between the perforations on both sides of the film, and its height occupies the equivalent of four consecutive perforations, and this area is known as the full screen aperture. : 1 . And the talkie film industry is progressing, and the ratio of 4:3 has also remained, but the image area has become less long and wide in order to make it easier to leave a place for the Sound Track, as it occupies a space on one side of the image. This new size is known internationally as the Academy Aperture, meaning the Academy Aperture, and these same names apply to the camera window, whether it is the Full Screen aperture or the Academy Aperture. When wide screen projection methods were invented, the ratio of width to length of the image displayed on the screen became Aspect Ratio =
(1.66:1) sometimes or (1.75:1) or
(1:185) or (1:2.2) or (1:35:2), it became necessary to change the size of the camera window as shown in Table No. 101 on pages 200 and 201.

Third: Anamor lenses in you
Anamorphic Lenses:

They are lenses used in photography in preparation for the disease on the broad screen, and it may be placed in front of the original lens as an additional piece or the original lens combined with the you've lens in you to be one lens. Whether this or that method is followed, they are lenses that cause anamorphosis intentionally, calculated with extreme precision, and this anamorphosis is in the form of horizontal compression only, not vertical compression. As an explanation for this, we say that assuming that we were going to photograph a perfectly round ball in nature, and we photographed it with a VIC lens that compresses the image in a ratio of 1:2, then this ball will appear oval in the image, and its width will be half its length in the image.

As a second example, we mention that assuming that the width of the scene being photographed is = 4 meters and its height is 1.5 meters, then we photographed it with an Ana Mor Vic lens whose compression ratio to the image is a Lens Squeeze Ratio of 2:1, which means that this scene will only compress its width by a ratio of 1:2. As for its length, it will remain the same, and thus the aspect ratio (width/height) of the image recorded on the negative film = 15:2.

For example, in the case of using anamorphic lenses for filming purposes, the 35 Cinema scope or I-Vision 35 mm, then the “camera window” is equal to the height of the full screen aperture (735 of an inch), while its width is equal to the width of the Academy aperture (6 of an inch). inch) and the image recorded on the film is squeezed by an Anamorphic lens at a ratio of 1:2, then the image is unsqueezed by a projector lens at a ratio of 1:2 as well.

It is the pressure value of the anamorphic lens, so the image width-to-length ratio becomes 2.35:1 when we see it on the screen.

It is hoped that we should mention in this regard that it is not only the size of the camera window or the amount of pressure that the negative image receives during imaging with the digital lens and your hips are the two factors that determine the aspect ratio of the image displayed on the screen Aspect Ratio in the conditions of multiple imaging methods in preparation for the disease on the screen Wide Screen Projection. Rather, the Projector aperture window also plays a role in this field, and the lens of the disease device may contribute to determining the final ratio of the disease to the length of the image on the screen. Aspect Ratlo

We will find in the following tables that the horizontal and vertical viewing angles are not considered absolute values, but rather they are relative values ​​that differ according to several factors, for example assuming that a lens with a specific focal length is used.
(60 Mali, for example) and the camera window was equal to 0.868 x 631 0 of an inch (ie the aperture of the academy), so the horizontal angle allowed by the width of 1868 0 of an inch is equal to 8 24 degrees, even if we used a lens with this same focal length in the photography preparation For disease using the Cinema Scope method (035 to) in which the size of the camera window is equal to
868, 0 x 735, 0 of an inch, you'll see that the horizontal angle
(which is allowed by the width of the window, which is 0.868 of an inch) is equal to 4706 degrees. It is seen that despite the agreement of the width of the camera window in both cases (which is 0.868 of an inch), the horizontal angle has changed a lot, and this is due to the fact that the image in the case of filming using the cinemascope method is compressed in a ratio of 2: 1 with an Anamorphic lens in the horizontal direction.

Likewise, the angle of the lens changes if the marks that define the visible view on the ground glass marking in the viewfinder are taken into consideration.
View finder despite using the same camera and the same lens.

And we show in the following table an example of what we notice when imaging the disease using the cinemascope method, according to what was stated in Table No. 91. . p. 186.

How to make use of the following tables
(From Table No. 88 to No. 99)

Example: What are each of the following: the horizontal and vertical angles between which the view that will be recorded on the film is confined if the filming was done with a lens whose focal length is 50 millimeters, and it is desirable that the positive film be displayed on a wide screen in which the image’s aspect ratio is to its length. 85, 1:1

Answer: From Table No. 89 p. 184, we conclude the following:

​​​​​​ - The horizontal angle = 23.7 degrees and the vertical angle = 12.9 degrees. Note: For more information about the imaging methods mentioned, starting from (Table No. 89 page 184 - . - to Table No. 97 page 192), please Refer also to Table No. 101 in its two parts on pages 200 and 201 of the book, and the explanation related to Table No. 101 starting from page 196