About camera diopter adjustment and other related camera problems

Some high-end cameras have added diopter adjustment devices to facilitate people with mild myopia or presbyopia to watch the effect directly in the viewfinder without glasses. In fact, the diopter adjustment device is to add a group of lenses to the eyepiece of the camera, and adjust the position relationship of the lenses through the knob to realize continuous diopter conversion within a certain range. The range is generally between -3D and +2D. Because the diopter adjustment range is limited, users with moderate myopia beyond this range can choose a special eyepiece adjustment mirror. The eyepiece adjusting mirror specially developed for myopic users has diopters of-1, -2, -3, -4, etc. The eyepiece adjusting mirror specially developed for hyperopia users has diopters of +0.5,+1,+1.5, +2 and +3 respectively. Pixel is usually considered as the smallest complete sample of an image. Pixel refers to the resolution of a digital camera, which is determined by the number of photosensitive elements on the photoelectric sensor in the camera, and one photosensitive element corresponds to one pixel. Therefore, the larger the pixel, the more photosensitive elements, and the greater the corresponding cost. The image quality of a digital camera depends in part on the pixels. When it is larger than a certain size, it is meaningless to simply compare it with pixels, because the resolution of the display we use is limited, generally between 1024×768 and 1920× 1200. If a picture with too high pixels is displayed at this resolution, the picture will be compressed to the size of the current screen, and some pictures will appear sharp at this time. The imaging quality mainly depends on the size and quality of camera lens and photosensitive element. The larger the pixel, the higher the resolution of the photo and the larger the printable size. The largest pixel is obtained by interpolation. Effective pixel number refers to the pixel value that really participates in photosensitive imaging. The effective number of pixels is the key to determine the picture quality. Each pixel is the smallest unit in a digital picture. The larger the pixel, the larger the area of the picture. For a digital camera, there are two main factors in the imaging of an image sensor: one is the area of the sensor; The second is the color depth of the photosensitive element. The larger the area of the photosensitive element, the greater the imaging. Under the same conditions, more image details can be recorded, the interference between pixels is also small, and the imaging quality is better. Color depth, that is, color bit, is how many binary digits are used to record the three primary colors. Generally, the photosensitive elements of non-professional digital cameras are all 24 bits, while the sampling of high-end points is 30 bits, but it is still 24 bits when recording. The imaging element of a professional digital camera is at least 36 bits. For a 24-bit device, the maximum brightness value that the photosensitive unit can record is 2 8 = 256, each primary color is represented by an 8-bit binary number, and the maximum color that can be recorded is 256x256. For 36-bit equipment, the maximum brightness value that the photosensitive unit can record is 2 12 = 4096, and each primary color is represented by a binary number of 12, and the maximum number of colors that can be recorded is 4096x4096x4096, which is about 6.87 billion. For example, if the brightness of the brightest part of the subject is 400 times that of the darkest part, shooting with a digital camera with a 24-bit photosensitive element, if the subject is exposed in a weak light part, all the parts with brightness higher than 256 will be overexposed, and the layer will be lost, resulting in bright spots. If the subject is exposed in the highlight, then the part below a certain brightness will be underexposed. If you use a professional digital camera with 36-bit photosensitive elements, sensitivity is a commonly used term in traditional cameras, indicating the sensitivity of film to light. ISO sensitivity is divided into100,200,400. The higher the sensitivity, the more suitable for shooting in dim light. But at the same time, the vividness and authenticity of the color will also be affected. Although digital cameras don't use film, their functions are similar. The CCD sensitivity (ISO sensitivity) of digital camera is equivalent to the sensitivity of traditional film, and the ISO sensitivity can be changed by setting. ISO of digital camera is realized by adjusting the sensitivity of photosensitive devices or merging photosensitive points, that is, by improving the sensitivity of photosensitive devices or merging several adjacent photosensitive points, the ISO can be improved. Photosensitive devices have a kind of reaction ability and are fixed. Improving the ISO of digital cameras can be achieved in two ways: 1, forcibly improving the brightness and contrast of each pixel; 2. Using multiple pixels * * * can complete the task that only one pixel is needed. It can be seen that the image quality loss of digital cameras after upgrading to ISO is great, especially when the area of photosensitive devices is small, the improvement of ISO image quality will be greatly reduced. The influence of sensitivity on photography is manifested in two aspects. One is speed. Higher sensitivity can get faster shutter speed and be easier to understand. The second is image quality. The lower the sensitivity, the finer the image quality, the higher the sensitivity and the higher the noise.