מצלמת מכשירים אופטיים

מאמר על מצלמת מכשירים אופטיים

חלקי המצלמה

מצלמה פשוטה מורכבת מעדשה קמורה, דיאפרגמה, תריס ופילם.

עדשות קמורות מתפקדות ליצירת תמונה אמיתית והפוכה על גבי הפילם. בניגוד לעדשת העין, שאורך המוקד שלה יכול להשתנות, לעדשת המצלמה יש אורך מוקד שאינו יכול להשתנות. עדשת המצלמה היא עדשה קמורה, לא עדשה... עדשה קעורה מכיוון שהתמונה המופקת על ידי העדשה הקעורה היא תמיד וירטואלית. במקום זאת, התמונה המופקת על ידי עדשה קמורה היא אמיתית כאשר מרחק העצם גדול מאורך המוקד. תמונה אמיתית היא תמונה שקיימת משום שניתן להקליט תמונה זו על סרט. לעומת זאת, התמונה הווירטואלית היא תמונה כוזבת, כך שלא ניתן להקליט אותה על סרט. מיקום התמונה האמיתית וההפוכה המופקת על ידי העדשה הקמורה חופף למיקום הסרט.

Diaphragm or f-stop. The diaphragm functions to control the amount of light that affects the film. The size of the opening diameter depends on the size of the lens and is expressed by the f-number or f-stop. F-Stop is defined as the ratio of the focal length of the lens (f) to the diameter of the opening (D): f-stop = f / D. If the lens has a focal length of 100 mm and the opening diameter is 20 mm, then the lens has a f-stop of 100 mm / 20 mm = 5. In this case, the lens is set at f / 5. If the lens has a focal length of 100 mm and the opening diameter is 25 mm, the lens has an f-stop of 100 mm / 25 mm = 4. In this case, the lens is set at f / 4. Based on this calculation, it is concluded that the higher the diameter of the opening, the smaller the number of f-stops and the lighter about the film. The smallest f-stop number (the most significant opening diameter) is the speed of the lens.

Shutter speed. The length of the open shutter time interval affects the amount of light that hit the film because when the shutter opens, the film also opens and is subjected to light. Shutter speed is also called “lighting time”. The shutter speed is related to the shutter time interval open. Therefore, the shutter speed is expressed in seconds. The shutter speed is between several seconds to a second. The smaller the time interval for the shutter to open, the faster the shutter speed, the less light will hit the film. Fast shutter speed is needed when the amount of light is small. Fast shutter speed is also required to eliminate image blur due to camera movement.

סרט צילום. The film functions to record the real image formed by the camera lens. A few years ago, the film was still used on the camera, but now the film is no longer used on the camera. At present, the image formed by the camera lens are recorded electronically. Cameras that record images electronically are called digital camera. Cameras that record image using a film are called analog camera.

Focusing and formation of the image

The quality of the shooting, in addition to depending on the size of the diaphragm opening and shutter speed, is also affected by focusing. Before reviewing the focusing of the camera lens, first understand the following explanation. Regarding convex lenses, it is explained that if the object distance (s = do) is very far and is considered infinite, the real image produced by a convex lens coincides with the focal point of the convex lens. So, when the object distance is infinite, the image distance (s’ = di) is equal to the focal length (f). Regarding the image formation of the convex lens, it is learned that if the object distance gets smaller, the image distance gets more prominent and the image size is also getting bigger.

Focusing the camera lens is different from focusing the eye lens. Focusing on the eye lens is done by changing the curvature of the eye lens (changing the focal length of the eye lens) until the image falls right on the retina so that the most precise image is produced. If the camera uses a single lens (not a zoom lens that has many lenses), the focal length of the lens cannot be changed. Focusing the camera lens is done by changing the image distance (di) until the most precise image is produced.

If the object distance (s = do) is very far or infinite, the image distance (di) is the same as the focal length (f). Compare Figure 1.

If the object distance is smaller than infinite, the image distance (s’ = di) is greater than the focal length (f). The smaller the object distance (s = do), the higher the image distance (di) and the higher the image size. Based on this explanation, it is concluded that if the distance between the object and the lens are closer, the distance between the lens and the film must be enlarged. If the distance between objects with the lens farther away, the distance between the lens and the film is reduced. Compare Figure 2.

Focusing on the camera lens also needs to pay attention to the focal length of the camera lens used. The larger the focal length of the camera lens, the higher the image distance (s’ = di). Lenses that have a higher focal length also produce the larger image. If we want to get a precise figure while the distance of an object is distant, use a lens that has a large focal length. Lenses that have a large focal length are usually flatter or less curved.