Dajiang lens parameters
The following are some of the Djiang lens parameters: - **DJI PL PZ 17 - 28mm T3.0 ASHH lens **: - The lens frame was full frame (36* 24mm). The lens was used as a movie lens. The lens type was zoom. The lens structure was 11 sets of 13 pieces. The lens mount was a PL mount. The filter size was 67mm. - In terms of optical parameters, the maximum aperture was T3.0, the minimum aperture was T22, the focal length range was 17 - 28mm, the closest focusing distance at the 17mm end was 0.19m, and the closest focusing distance at the 28mm end was 0.26m. - The diameter of the lens was 78mm, the length of the lens was 117.2 mm, the weight of the lens was about 520g, the working temperature was-10 ° C to 55 ° C, the storage temperature was 10 ° C to 35 ° C, and the storage humidity was 45% to 75%. - **DJI TL 75mm F1.8 lens **: It is suitable for the 75mm medium telephoto focal length of Zenith X9 - Air lens. The F1.8 large aperture can capture a richer depth of the picture. It has a shallow depth of field and a larger amount of light. It can enhance the performance of the main body and the night scene. It weighs only 269 grams. Read more exciting novels for free
Single lens reflex lens parameters
The angle of view of the medium focal length lens was between 40 degrees and 18 degrees, and the focal length range was between 61mm and 135 mm. The angle of view of a standard/medium-focus lens was about 40 - 55 degrees. In terms of optical characteristics, the photos taken at this focal length had the least distortion and could accurately reflect the shape of the subject. It was also relatively easy to design a large aperture. Different models of medium-focal lenses had different performance parameters in terms of distortion, dispersion, resolution, contrast, and so on. For example, the Olympus OM Zuiko auto-macro 90mm f/2.0 lens had an actual focal length of 90.44mm, an aperture of f/2.04, a pincushion-shaped distortion of 0.47%, and an edge loss of 0.3 stops at f/5.6. Minolta MC Rokkor -85mm f/1.7 lens, the actual test focal length was 85.6mm, with 0.5% barrel distortion, etc. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
The optical parameters on the lens
The following is some common optical parameters on the lens: 1. ** effective focal length (EFL)**: The distance from the center of the lens to the focal point. It could be divided into image focal length (the distance between the main surface of the image and the focal point of the image) and object focal length (the distance between the main surface of the object and the focal point of the object). If the focal length is too short, it will cause the field of view to be too large, causing distortion, difficulty in controlling the angle of the chief ray, low contrast, serious lens bending, difficulty in correcting the phase difference, and other problems. If the focal length is too long, the lens will be too long, which is not conducive to the miniaturized system. Moreover, the field of view is too small to meet the user's needs (FoV>60°). 2. ** Total length of lens (TL)**: It is divided into optical length (the distance between the first surface of the lens and the image surface) and mechanism length (the distance between the end of the lens barrel and the image surface). 3. ** Back focal length (BTL)**: The distance from the last side of the lens in the optical system to the image plane. 4. ** Front focal length (FFL)**: The distance from the first surface of the lens to the object surface in the optical system must be distinguished from the back focal length of the mechanism. 5. ** Mechanical back focal length (FTL/FFL)**: The distance from the last mechanical surface of the lens group to the image surface. 6. ** Field of View (FoV)**: The largest field of view that the camera can capture. It can be divided into diagonal field of view (FoV-D), horizontal field of view (FoV-H), and vertical field of view (FoV-V). The diagonal field of view is the largest, followed by the horizontal field of view, and the vertical field of view is the smallest. The so-called field of view refers to the diagonal field of view of the digital camera module. The size of the field of view was related to the focal length. Generally, the larger the field of view, the shorter the focal length. 7. ** Joules (F/NO.)**: It was the ratio of the effective focal length to the diameter of the pupil, which was used to determine the brightness of the lens. Under the premise of ensuring the same aperture, the shorter the focal length, the smaller the relative aperture should be. In general, the smaller the F/#, the larger the aperture. 8. Distortion: It is the off-axis phase difference. It is the height difference between the intersection point of the off-axis point and the main ray on the image plane and the ideal (paraxial-like) image plane. It is a function of the field of view and has nothing to do with the aperture. Distortion was divided into TV distortion and optical distortion. TV distortion was further divided into pillow type and cylinder type. Distortion is the image quality that users can easily feel. Different application scenarios have different requirements for distortion. For example, Optical-Distortion <3% is not easy to detect by the human eye, and the objective lens generally requires Optical-Distortion <2%. 9. ** relative illumination (Ri)**: The ratio of the central illumination to the peripheral illumination. If the contrast was too low, the center of the image would be bright and the surroundings would be dark (vignette phenomenon, commonly known as dark corners), which would also cause color distortion. The Ri is directly proportional to COS4 (semi-fov). Different semi-fov correspond to different theoretical values of the Ri. When the Ri<50%, the human eye can distinguish it. In serious cases, the four corners of the picture will be completely black. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Canon lens parameters
Canon lenses had many parameters: ** 1. Type of bayonet ** 1. **EF** - It can be used directly on Canon's Canon's Canon 'Canon's Canon' Canon 2. **EF - S** - Canon's APS-C frame DSLR lens could not be directly installed on a full-frame DSLR. It could be used on the Eos-M series micro-lens and the Eos-R full-frame micro-lens through the transfer ring. 3. **EF - M** - Canon's Canon 'Canon's Canon's Canon 4. **RF** - Canon's Canon 5. **MP - E** - For macro photography, only MP-E 65mm f/2.81 - 5x. 6. **TS - E** - The electronic control shifted the lens. ** 2. Focus ** - The focal length in the lens model was the physical focal length. Standing in the same position, a small focal length meant a wide field of view, and a large focal length meant a good range of vision. For non-full-frame cameras, the actual use may need to consider the equivalent factor conversion according to the camera model. For example, the focal length range of the lens was 70 - 200mm, the angle of view at the 70mm end was relatively narrow, and the telescope ability at the 200mm end was better. ** 3. Maximum aperture ** 1. ** Permanent Aperture ** - For example,"f/2.8" could be set to this aperture value over the entire focal length range. For example, the EF70 - 200mm f/2.8 lens was a constant aperture lens. 2. ** Floating Aperture ** - Two numbers like "f/3.5 - 5.6" indicated that the maximum aperture changed over the entire focal length range. ** 4. Screen Level Identification ** - **L (Luxury) logo ** - It would only appear in Canon's professional lens identification information. It was the logo of the top Canon civilian lens. These lenses usually had a red decorative ring on the front end (red circle head). ** 5. Function ID ** 1. **IS (Image Stabilizer)** - This type of lens was equipped with Canon's unique image stabilizing device, which could offset the image blurring caused by hand shaking within a certain range. It was commonly used in Canon's high-end professional lenses. 2. **USM (ultrasonic motor)** - The lens using USM technology could achieve silent and fast-response autofocus. It was divided into three types: micro, ring, and NANO. There was also the STMs (Stepping Focus Machines), which were divided into two types: gear type and lead screw type. 3. **AL (Aspherical lens)** - It showed that the lens was designed with aspheric lenses to reduce the number of lenses. While reducing the weight and volume, it could provide better optical performance. It could solve the glare and edge distortion problems in wide-angle and zoom lenses, and it could also improve the optical quality of telephoto lenses. 4. **DO (Diffraction Optics)** - Lenses marked with this logo were equipped with multi-layered diffusing optical lenses, which had the characteristics of both fluorite and aspheric lenses. They were generally high-end Canon lenses. 5. ** DPS (a coating technology that optimized bokeh)** - It was commonly used in some Canon lenses to enhance the bokeh effect. 6. ** S-ud (S-ud glass) and UD (UD glass)** - The optical performance of S-KD glass was close to that of fluorite. The effect of one S-KD lens was equivalent to that of one fluorite lens, and the effect of two KD lenses was equivalent to that of one fluorite lens. These labels indicated that the lenses used the corresponding glass lenses. 7. **EMD (Electromagnetic Aperture)** - Lenses with this technology could open and close the aperture by electronic control. 8. **Float (Floating Function)** - When shooting at close range, the floating lens would compensate for the aberrations at close range to obtain better image quality. 9. ** CP (Focus Preset)** - It was Canon's high-end professional lens logo. The focus preset function allowed the lens to remember a certain focus distance. After setting the distance, the lens could automatically return to the set focus distance. This focus recovery function was even effective in manual focus mode. 10. ** ft-m (full-time manual)** - Canon lenses were equipped with full-time manual operation. The focus of the lens could be adjusted manually in the AF-mode. 11. ** Marco/macro ** - It means that the camera has a strong close-up ability. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Sony DSLR lens parameters
The following are some of the parameters related to common Sony-grade DSLR lenses: ** 1. Focus ** 1. ** SonyMDT18 - 135mmF3.5 - 5.6Sam**: The focal length range is 18 - 135mm. 2. ** PE PZ 28 - 135mm F4G OSS**: focal length 28 - 135mm. 3. ** ESF-S 18 - 200**: The focal length range is 18 - 200mm. 4. ** Sony70 - 400mm F4 - 5.6G SSM**: The focal length range is 70 - 400mm. 5. ** SonyFE24 - 240mmF3.5 - 6.3OSS**: The focal length range is 24 - 240mm. 6. ** SonyFE24 - 70mmF2.8GM**: The focal length is 24 - 70mm. 7. ** SonyFE24 - 105mmF4 **: The focal length range is 24 - 105mm. ** 2. Maximum aperture ** 1. ** SonyMD18 - 135mm F3.5 - 5.6Sam**: It is a floating aperture lens, and the maximum aperture changes between F3.5 - 5.6. 2. ** PE PZ 28 - 135mm F4G OSS**: A constant aperture lens with a maximum aperture of F4. 3. ** ESF-S18 - 200**: The maximum aperture is F2.8. 4. ** Sony70 - 400mm F4 - 5.6G SSM**: It is a floating aperture lens, and the maximum aperture varies between F4 - 5.6. 5. ** SonyFE24 - 240mmF3.5 - 6.3OSS**: It is a floating aperture lens, and the maximum aperture changes between F3.5 - 6.3. ** 3. Identification and characteristics of the lens type ** 1. ** PE **: E-mount full-frame lens, suitable for all E-mount devices. 2. **E**: E-mount APS-C frame lens, can be installed on all E-mount devices, but when paired with a full-frame camera, there will be frame trimming by default (only the central part of the CPU is used). If the image is not trimmed, there will usually be obvious halation or black blocking. 3. **G**: Inherited from Minolta's high-end lens logo, most of them have nano-coating. 4. **ZA**: A lens product jointly developed by Sony and Zeiss. The lens body and packaging have the double logo of Sony and Zeiss, all with T* coating. The lens may also have the words representing the lens structure (such as Warrio-Tessar, Planer, Distagon, Sonnar, etc.). There is no new product since July 2016. 5. GM (G-Master or "G-Master"): It was the highest-end lens product line from Sony, and all of them were nano-coated. ** 4. Other characteristics ** 1. ** PE PZ 28 - 135mm F4G OSS**: It has a power zoom function, which can provide smooth angle conversion and anti-shake function. 2. ** ESF-S18 - 200**: Automatic focus and anti-shake support. 3. ** Sony70 - 400mmF4 - 5.6G SSM**: It has SSM (ultrasonic motor), which is good for autofocus operation. 4. ** SonyFE24 - 240mmF3.5 - 6.3OSS**: With OSS (optical image stabilization system). <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Soviet camera lens parameters
The following are some of the parameters of the Soviet camera lens: - HELIOS44 58/2 lens ("Eight-feathered monster"). The specific parameters were not mentioned. - Mir - 1 2.8/37 lens: 37mm focal length (37.38mm), aperture ratio 1:2.8, field of view 60°, frame size 24x36mm, number of lenses/groups 6/5, front focal length-3.49mm, back focal length 37.17mm, distance from the first surface to the last surface 52.8mm, working distance (45.2mm for Mir - 1, 44.0mm for Mir - 1 -auto, 45.5mm for Mir - 1V), aperture ratio limit of 1:2.8 - 1:16, close-up focus limit of 0.7m, resolution of 45/23 lines/mm according to specifications (center/edge), light transmission rate of 0.78, connection (Lens-to-camera: Mir - 1 is M39×1, Mir - 1 -auto mount)(f/a Kiev - 10), Mir - 1V for M42×1; for screw attachment: Mir - 1 for Sp M49×0.5, Mir - 1V for M49×0.75; for snap-on attachment 51mm), overall size (The length of the lens with the lens cover: Mir - 1 is 62mm, Mir - 1V is 56mm, the largest frame diameter is 59mm), weight (Mir - 1 is 200g). - "JUPL- 9"("JUPL- 9" 2/85) lens: focal length 84.51MM, aperture 1:2 to 1:16, field of view 28 degrees 51 minutes, filter size M49*0.75MM, closest focusing 0.8M, seven pieces in three groups, the middle and back two parts are made of three lenses, the resolution is 32 lines/MM in the center, 23 lines/mm at the edge, volume 65(diameter)* 66mm, weight 0.36kg. - A particular camera had a focal length of 50mm and a clear aperture of 1:3.5. It was a three-piece, three-group orthoscope. The lens could be disassembled, and the shutter speed range was 1 - 1/1000. It also had a T-door and a B-door. There were ten levels of speed regulation, but the specific name of the lens was not mentioned. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Interpretation of the parameters of the Tuli lens
The interpretation of the parameters of the Tuli lens involved many aspects: ** 1. Usage and Type of the lens ** 1. ** Usage of the lens ** - There were wide-angle lenses and other lenses for different purposes. For example, some lenses were designed for wide-angle shooting. Different uses determined the angle of view and imaging characteristics of the lens. The wide-angle lens could shoot a wider scene, suitable for shooting scenes such as landscapes and buildings. 2. ** Shot Type ** - There is a zoom lens type. The zoom lens could adjust the focal length within a certain focal length range, allowing the photographer to change the viewing range of the picture without changing the lens, providing more flexibility in shooting. ** 2. The lens mount ** - For example, the Sony-alpha mount. The lens mount determined the type of camera body that the lens could fit into. A lens with a different mount could not be directly installed on a camera with a different mount. ** 3. size of the filter ** - It was expressed in terms of 77mm. The filter size was the parameters that needed to be paid attention to when installing the filter. Only the appropriate filter size could be installed on the lens. The filter could be used to adjust the light, color, and other effects. ** 4. Aperture related parameters ** 1. ** Maximum Aperture ** - For example, F2.8. The maximum aperture determined the maximum amount of light that entered the lens. A larger aperture could be used in low-light environments with a higher shutter speed or a lower IQ value. At the same time, it could also produce a shallow depth of field effect and highlight the subject. 2. ** Smallest Aperture ** - For example, F22. The smallest aperture was used in scenes that required a small aperture, such as large depth of field landscape photography. A small aperture could allow the image of the near and far scenes to be clear. 3. ** Number of Aperture Blades ** - For example, nine aperture blades. The number of aperture blades would affect the shape of the aperture. A larger number of aperture blades could make the aperture closer to a circle, which could produce a more rounded and natural light spot effect when blurring the background. ** 5. Focus related parameters ** 1. ** Nearest Focus Distance ** - For example, 0.3m. The closest focus distance represents the shortest distance that the lens can focus. When the shooting distance is less than this value, the lens cannot focus clearly. This was very important when taking close-up or macro photos. 2. ** Maximum Magnification ** - For example, 0.086 times. The maximum magnifying power reflected the degree to which the lens could magnify the subject. A larger magnifying power would help to take close-ups of small objects. ** 6. Range of View ** - For example, a range of 104 - 82 degrees. The angle of view determined the range of the image that the lens could capture. The wide-angle lens had a larger angle of view and could capture a wider scene. The telephoto lens had a smaller angle of view and was suitable for capturing distant objects or compressing space. ** 7. Other parameters ** 1. ** Lenses diameter, length and weight ** - These parameters affected the lens's mobility and the camera's overall weight. For example, the lens diameter was 77mm, the lens length was 84.1mm, the lens weight was 560g, etc. The heavier and larger lens may require more stable support equipment when carrying and using. 2. ** Repair Information ** - For example, you can enjoy a nationwide guarantee, three guarantees, and a one-year guarantee. This was related to the after-sales guarantee if the lens had any problems during use. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Nikon lens parameters setting
There were many parameters for Nikon lenses. The following are some of the main parameters: ** 1. Type of bayonet ** 1. **F mount ** - The FX-lens was suitable for all of Nikon's DSLR cameras, similar to Canon's EF-lens, while the DX-lens was suitable for Nikon's APS-C format camera, similar to Canon's EF-S lens. - Generally speaking, the price of the DV lens was more affordable and could be regarded as an APS-C (half-frame) entry-level lens, while the XP lens was a professional lens and had a higher price. However, Nikon's DV lens could be installed on a full-frame camera, but it might produce black circles or dark corners. If you didn't have a full-frame lens on hand, you could replace it after trimming the image. - Among the Nikon AF-S and AF-F lens models, the ones with the word "DK" were called "DK" lenses, and the others were "FO" lenses. The capital letter N was more commonly seen on the lens body of the FO lens. 2. ** Z-mount ** - The Z lens was suitable for Nikon micro-cameras, similar to Canon M-series lenses. ** 2. Type of motor ** 1. **AF** - This lens does not have a focus motor. You need to use a body equipped with a motor to achieve autofocus. 2. **AF - I** - It meant that the lens had a built-in motor design. 3. **AF - S** - It meant that the lens had a built-in ultrasonic motor design, which made focusing faster and quieter. Some half-frame lenses of Nikon also had this motor, which was different from Canon (Canon's similar logo was USM and was mostly used for full-frame lenses). 4. **AF - P** - It meant that the lens had a built-in stepping motor, similar to Canon's ATM logo. If there was the word (PC), it meant that the lens was a shift-axis lens. ** 3. Focus related parameters ** - Numbers such as 24 - 70mm/105mm on the lens indicate the focal length of the lens. The zooming lens was marked with the values at both ends of the focal length range, and the fixed-focus lens was represented by a single value. ** 4. Aperture related parameters ** 1. ** Maximum Aperture Value ** - For example, 1:3.5 - 5.6/1:2.8 represents the maximum aperture value. When the zoom lens had two values, they represented the maximum aperture of the wide-angle end and the telephoto end respectively; the fixed focal lens and the zoom lens used a single value to represent the constant maximum aperture. 2. ** Aperture Type ** - No Suffix meant that the lens had an aperture ring and could not provide distance information;D Suffix meant that the lens had an aperture ring and could provide distance information;G Suffix meant that the lens did not have an aperture ring but could provide distance information;E Suffix meant that the lens did not have an aperture ring, but an electromagnetic aperture could also provide distance information. E was more advanced than G. ** 5. Other parameters ** - II meant that the lens was a second-generation product. - TL, ED, PR, and so on indicate the type of lens used (Canon lenses do not indicate such information). - VR indicated that the lens had a shock absorption function, similar to Canon's IS logo. - N represents a special (nano) coated lens, which can effectively alleviate the ghostly shadows caused by red light and reduce the ghostly shadows and glare caused by the light entering the lens diagonally. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Canon lens shooting parameters
The common shooting parameters of Canon lenses were as follows: - ** Shot Type **: - "EP: Can be used with Canon's Canon's Canon 'Canon's Canon' Canon - ESF-S: Canon's APS-C frame single-lens reflex lens. It can't be directly installed on a full-frame single-lens reflex. It can be used on the eos-M series micro-lens and eos-R full-frame micro-lens through the transfer ring. - "ESF-M: Canon's Eos M series micro-lens. It cannot be used on other Canon cameras. - <<PR>: Canon's Eos R series full-frame micro-lens. It cannot be used on other Canon cameras. There were also MP-E (specialized for macro photography) and TS-E (electronic controlled shift lens), two special products. - ** focal length of lens **: A small number means a wide angle of view, and a large number means a good telescope. The focal length in the lens model is the physical focal length. For non-full frame cameras, you may need to consider the equivalent factor conversion according to the camera model. - ** Maximum Aperture **: For a zoom lens, if it is in the form of "f/2.8", it means that it is a constant aperture lens, and the entire focal length range can be set to this aperture; if it is similar to "f/3.5 - 5.6", it is a floating aperture lens, and its maximum aperture changes over the entire focal length range. - ** Lenses Grade **: L (Luxury) means Canon's high-end lenses, which are red circle lenses. These lenses usually have a red decorative ring at the front. - ** Image Stabilizer **: The IS (Image Stabilizer) logo indicates that the lens is equipped with Canon's unique image stabilizer, which can offset the image blurring caused by hand shaking within a certain range. It is commonly used in Canon's high-end professional lenses. - ** Focus motor **: - USM (Ultra-Sonic Motor): The lens using USM technology can achieve silent and fast-response autofocus. It is divided into three types: micro, ring, and NANO. - <strong></strong> - ** Other Marks **: - AL: It means that aspheric lenses are used in the lens design, which can reduce the number of lenses, reduce weight and volume, and provide better optical performance. It is used to solve the problems of glare and edge distortion in wide-angle and zoom lenses. It can also improve the optical quality of telephoto lenses. - DO: Lenses marked with this logo are equipped with multi-layer reflective lenses, which have the characteristics of fluorite and aspheric lenses. They are generally high-end lenses. - EMD: It means that the lens can open and close the aperture by electronic control. - Float: When the lens is used for close-up shooting, the lens will compensate for the aberrations at close range to obtain better image quality. - XP: The lens with this logo is a high-end professional lens. It has a focus presetting function that allows the lens to remember a certain focus distance. After setting it, it can automatically return to the set focus distance. It is also effective in manual focus mode. - FT - M: A lens with full-time manual function. You can manually adjust the focus of the lens in autofocus mode. - S-KD: It means that the lens uses S-KD glass lenses, and its optical performance is close to that of fluorite. The effect of an S-KD lens is equivalent to that of a fluorite lens. - KD: It means that the lens is made of KD glass lenses. The effect of two KD lenses is equivalent to that of a fluorite lens. - <MACRO>: This means that the lens has a strong close-up ability. - [DPS: A coating technology that optimized bokeh.] <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
hitachi projection lens parameters
The parameters of the Hitachi projection lens were different. For example, the parameters of one projection lens were F = 1.7 - 2.1, f = 36.8 - 47.8mm; the other was F = 1.74 - 2.08, f = 36.8 - 47.8mm; and the zooming method was a zooming lens (F = 1.7 - 2.1, f = 24 - 29mm). <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
The technical parameters of the optical lens
The main technical parameters of the optical lens were as follows: 1. ** effective focal length (EFL)**: The distance from the center of the lens to the focal point. It was further divided into image focal length (the distance between the main surface of the image and the focal point of the image) and object focal length (the distance between the main surface of the object and the focal point of the object). If the focal length is too short, the field of view will be too large, resulting in distortion, difficulty in controlling the main ray angle, low contrast, serious lens bending, difficulty in correcting the phase difference, and other problems, which is not conducive to the design; if the focal length is too long, the lens will be too long, which is not conducive to the miniaturized system. If the field of view is too small, it is difficult to meet the user's needs (FoV>60°). 2. ** Total length of lens (TL)**: It is divided into optical length (the distance between the first surface of the lens and the image surface) and mechanism length (the distance between the end of the lens barrel and the image surface). 3. ** Back focal length (BTL)**: The distance from the last side of the lens in the optical system to the image plane. 4. ** Front focal length (FFL)**: The distance from the first surface of the lens to the object surface in the optical system must be distinguished from the back focal length of the mechanism. 5. ** Mechanical back focal length (FTL/FFL)**: The distance from the last mechanical surface of the lens group to the image surface. 6. ** Field of view (FoV)**: refers to the largest field of view that the lens can capture. It can be divided into diagonal field of view (FoV-D), horizontal field of view (FoV-H), and vertical field of view (FoV-V). The diagonal field of view is the largest, followed by the horizontal field of view, and the vertical field of view is the smallest. The so-called field of view usually refers to the diagonal field of view of the digital camera module. 7. ** Joules (F/NO.)**: It is the ratio of the effective focal length to the diameter of the entrance pupil, which is used to determine the brightness of the lens. Under the premise of ensuring the same aperture, the shorter the focal length, the smaller the relative aperture should be. In general, the smaller the F/#, the larger the aperture. 8. ** Distortion **: It is the off-axis phase difference. It is the aberrations of the off-axis thin beam. It is the height difference between the intersection point of the off-axis point and the main ray on the image plane and the ideal (near axis) image plane. It is a function of the field of view and has nothing to do with the aperture. The primary distortion changes with the cubic power of the field of view (image height), and the percentage distortion increases with the square of the image height. The distortion varies with different fields of view, and the distortion changes are non-linear. It is only the distortion of the image and does not affect the clarity of the image. Distortion is divided into TV distortion and optical distortion. TV distortion is further divided into pillow type and cylinder type. Different application scenarios have different requirements for distortion. For example, Optical-Distortion <3% is not easy to detect by the human eye, and Optical-Distortion <2% is the distortion requirement of the photographic objective lens. 9. ** relative illumination (Ri)**: The ratio of the central illumination to the peripheral illumination. If the contrast was too low, the center of the image would be bright and the surroundings would be dark (vignette phenomenon, commonly known as dark corners), which would also cause color distortion. The Ri is directly proportional to COS4 (semi-fov). Different semi-fov values correspond to different theoretical values of the Ri. When the Ri<50%, the human eye can distinguish it. In serious cases, the four corners of the picture will be completely black. 10. ** resolution **: It can be defined as the number of pairs of black and white stripes that can be distinguished in millimeters when the lens is used to observe the black-and-white grid pattern. When selecting a lens, the lens resolution is usually required to be slightly higher than the resolution of the picture element. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>