What do you mean by focus?

Question 1: What does the focal segment mean? If you have seen f = in the English manual of the camera, then the number behind it is usually its focal length, that is, the focal length. For example, f=8-24mm, 38-1 15mm (equivalent to 35mm) means that the focal length of this camera is 8-24mm, and the converted diagonal viewing angle is equivalent to 3×-115 mm. Generally speaking, the standard lens focal length of a 35mm camera is about 28-70mm, so if the focal length is higher than 70mm, it means that the telescopic effect is supported. If it is less than 28mm, it means that it has wide-angle shooting ability.

Focal range is the extension of focal length, which is usually divided into general shooting distance and close-up distance. The general shooting distance of a camera is usually marked as from a certain centimeter to infinity, and advanced design products often provide close-up shooting function (macro) to make up for the problem of not focusing in general shooting mode. Some cameras emphasize the magical ability of supporting 1 cm close-up, which is suitable for shooting fine objects.

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Question 2: What are the concepts of photographic focal length and focal length? The physical definition of focal length is the distance from the center of the lens to the focal point. Because the photographic lens adopts multi-lens structure, the meaning of focal length is more complicated than the physical definition of single lens, so it can be considered that the lens has a theoretical single lens surface, which is easy to understand.

Photography is a process in which an object is imaged onto a sensor (negative) through a lens. The distance from the object to the theoretical lens surface of the lens is the object focal length, and the distance from the theoretical lens surface of the lens to the sensor is the image focal length.

Generally speaking, the focal length of a lens refers to the focal length of an image, and the focal length of photography essentially refers to the viewing angle of a shot, and the larger the focal length, the smaller the viewing angle.

The change of focal length does not affect the clarity of the image, but affects the range of the shot image.

Clarity is a matter of focusing, not focal length. Focusing is to make the focus of imaging fall right on the sensor. As long as the focus is accurate, any focal length imaging is clear.

The focal length is aimed at the zoom lens, and the focal length of the zoom lens can change in a continuous range, so the minimum focal length and the maximum focal length are written together, which is called focal length.

Question 3: What does full focal length mean? As far as zoom lens is concerned, it refers to the lens focal length from the shortest focal length end to the longest focal length end of the lens; As far as brand lens group is concerned, it refers to the focal length covered by the brand's wide-angle (fisheye) lens with the shortest focal length to the ultra-long focal length lens with the longest focal length.

Question 4: What does the focal length of SLR lens mean? The focal length is the focal length range of the zoom lens.

The division of lens focal length: first, the meter head-the so-called standard lens. Its viewing angle is about 43 degrees, and the viewing angle of the photo is closest to the human eye. Different frames have different title focal lengths. The standard lens of 135 film is about 50mm, the focal length of the 6×6 title of 120 is about 80mm, and the title of 300d is about 50 ÷1.5 = 33 mm. Documentary photos can faithfully record what you see by using the title, so most documentary photographers like to use the title, such as French photographers.

When the focal length is smaller than the pan/tilt, the lens can record images with a larger angle of view, so it is called a wide-angle lens. The perspective of a wide-angle lens is exaggerated. Under the wide-angle lens, the closer you are, the smaller you are, especially in landscape photography, you can take more photos with visual impact.

A lens whose focal length is 1.5 ~ 4 times larger than that of the meter head is called medium focus. Generally, the medium focus lens has the smallest deformation, and it is relatively easy to design it into a super-large aperture, so portrait photography is what the medium focus lens is best at. Generally, the focal length of the title is 1.5 ~ 2 times, which is used to take photos of the whole body and chest circumference. Shots larger than 2 times are mostly used for close-ups, and several shots called "portrait king" in the shot all appear in this focal part.

A lens that is more than twice the focal length of the head is called a telescope head. As the name implies, the telescopic lens can achieve "telescopic" shooting, which is mostly used to shoot sports, animals and so on. The application of telescope lens in scenery film can compress the far and near perspective of the scene.

Question 5: What does the number of lens focal length mean? The focal length of the lens represents the focal length of the lens. For example, the number of focal lengths in EF-S 18-200mm f/3.5-5.6 means that the focal length of this lens is continuously variable between 18mm and 200mm.

Question 6: What does the focal length of the lens mean? 18-200MM: First, the variable focal length lens, 18MM wide focal length and 200MM telephoto end. That is to say, the focal length can be arbitrarily lengthened or shortened between 18-200mm.

EF-S 55-250MM F4-5.6 IS: IS stands for anti-shake (electronic stabilizer), which means your hand is unstable. It can save you a little and prevent the photos from blurring (relative) because of shaking. F4-5.6 means that the maximum aperture of this lens is F4 of 55 focal length, and 5.6 is 5.6 of 250 mm focal length. The focal length has changed, so has the aperture. The aperture of the advanced lens is constant, such as 70-200 F2.8, which means that the maximum aperture can be kept at 2.8 whether you order 200 lenses at 70 terminals or not.

18-200mm is the focal length of the lens. The shortest focal length of this lens is 18mm, and the longest focal length is 200mm.

55-250mm f/4-5.6 IS, in which the focal length of the 55-250mm lens is the same as that mentioned above; F4-5.6 is the maximum aperture of the lens at the wide-angle end and telephoto end. EF-S IS the lens name used by Canon in APS scale, and IS is Canon's anti-shake lens.

Question 7: What does the focal length of the lens mean? 18 focal length is the range of lens focal length.

For example, evaluating the lens of 18- 135, it can be said that the focal length of this lens conforms to most shooting scenes.