Digital Camera terminology

When purchasing a digital camera, I believe many people will feel overwhelmed by the complicated parameters of the digital camera. Due to the rapid development of digital imaging technology, even those who often pay attention to this industry are often confused about some new technologies. Now let's talk about the definition of the main technical indicators on the market, hoping to help consumers buy digital cameras.
　　
I. Basic Knowledge pixel, photosensitive element, size, valid pixel, resolution
　　
Usually, consumers are most concerned with the camera's pixels. pixels are indeed the most important hard indicator of digital cameras. That is to say, high pixels are not necessarily good cameras, however, the pixel is too low (in the current mainstream market, if it is lower than 3 million), it cannot be regarded as a good camera.
　　
Pixels:
　　
First, let's talk about the photosensitive principle of a digital camera. To take a photo, you must first convert the optical signal into an electrical signal, which relies on the sensor ), there is a chip behind the lens of a digital camera, which is packed with these photosensitive elements. Each photosensitive element can only convert a very small point into an image, these small images add up to what we can see. Let's get to know a bit here. Good, pixels are actually the photosensitive elements. We usually say that the number of tens of thousands of pixels is the number of these photosensitive elements. Therefore, the larger the pixel, the clearer and more delicate the imaging. Of course, this is subject to many factors, which will be mentioned below.
　　
Next we will talk about the reason why high pixels are not necessarily good for cameras: Size
　　
Size:
　　
The size is generally referred to as the CCD size and CMOS size. Common ones include 2/3 inch, 1/1. 8 inch, 1/2. 7 inch. This unit is not too intuitive. Taking 1/2. 7 inch as an example, the unit we are familiar with is 5.27 × 3.96. With the same number of pixels, the more dense the arrangement, the more frequent the current interference between pixels, and the more frequent the noise interference imaging quality. So the larger the size, the better, the higher the cost, of course, will also increase-not in proportion, but in geometric progression. At present, 2/3 inch of machines are already quite advanced, such as d7hi of Meida, cp5700 of Nikon, and f717 of Sony, A few cameras that use the same size as the negatives of the 135 cameras we usually use, the price is even higher.
　　
　　
Figure 1: Comparison of various sizes
　　
Valid pixels:
　　
Most camera manufacturers use the total pixel to indicate the resolution of a camera. However, recorded pixels should be used to record pixels, which are not the same as valid pixels, however, people are used to using valid pixels instead of recording pixels.
　　
We use Sony's icx252aq 3.34 million pixel CCD to compare various "pixels ":
　　
Total pixels: 2140x1560 (3.34 million)
Photosensitive pixels: 2088x1550 (3.24 million)
Active pixels: 2080x1542 (3.21 million)
Recommended record pixels: 2048x1536 (3.14 million)
　　
Table 1: pixels
　　
Some of the total pixels are non-photosensitive, that is, bad pixels, which cannot be solved by the current technology; the rest of the pixels except for bad ones are photosensitive pixels, the edge of the photosensitive element must be used as a reference to determine the "black" value, and these pixels are not involved in imaging. Except for those not involved in imaging, the remaining pixels are active pixels; then some pixels are extracted from these pixels for a standard output (such as 2048x1536 ). In this way, we subtract the remaining recommendation record pixels, which we usually call effective pixels.
　　
Resolution:
　　
Resolution is directly related to valid pixels. For example, the maximum resolution of a 2 million pixel digital camera is 1704 × 1257, and that of a 3 million pixel digital camera is 2048 × 1536, the resolution is 2560 × 1920.
If you want to obtain the final photo by digital printing, the-million photo taken at the maximum resolution must be printed as a common 6-inch photo with a picture quality comparable to that of a normal film, A digital camera of over 5 million pixels can be used to produce posters and advertisements after printing. If you use an inkjet printer that is commonly used in your family to print photos on the photo printing paper, take the A4 format as an example. After the margins of the A4 size photo print paper are removed, the actual used area is 19 cm × 27 cm, the 3 million pixel standard meets the imaging requirements on A4 photo printing paper. If you only want to store photos on your computer, use a monitor to view them, even if you are using more than 17 inch mainstream display products, the resolution is greater than the mainstream 1024x768, the resolution provided by an ordinary 2 million-pixel digital camera can also be clearly displayed.
　　
After talking about photosensitive elements, you may still feel awkward, but when talking about CCD, you must be more comfortable. Yes, CCD is the most important photosensitive element in the current market. However, CCD should be used instead of simply replacing it, this is because the photosensitive element also has an important force-CMOS. The following describes their respective features and representative technologies.
　　
CCD: Charge coupler (charge-coupled device), the most important photosensitive device on the market, mature technology, sharp imaging, bright colors. Special technologies include the Super CCD technology developed by Fuji.
　　
Super CCD (Super CCD): Developed by Fuji, Super CCD is arranged in an staggered manner and has unique octagonal photosensitive elements, which can provide larger photosensitive elements for each pixel. The shape and arrangement of Super CCD sensors can generate a more balanced digital photo quality. The sensing degree has been further improved, and the dynamic range has also been improved. At the same time, it can improve the signal-to-noise ratio and provide higher resolution, better tones and more authentic colors. Super CCD is designed to control the total balance of these factors and aims to provide better image quality. Cameras using the Super CCD technology can achieve higher resolution than other models of the same pixel. However, in actual use, the Super CCD effect cannot be used to remove the opponent. Now the Super CCD has grown to the fourth generation, so we will not go into detail here.
　　
　　
Figure 2: Super CCD pixel Arrangement
　　
CMOS: Complementary Metal Oxide Semiconductor (Complementary Metal-oxide semicondu), CMOS imaging chip for digital cameras began in 1997, compared with the CCD chip widely used in digital cameras, the CMOS photosensitive chip has the advantages of low cost and low energy consumption. However, the technology is not very mature, and there are still few digital cameras using it as a photosensitive chip. The most famous is the foveon X3 Technology of foveon in the United States. In addition, Canon also widely uses CMOS as photosensitive elements in its high-end digital SLR cameras. However, Canon does not publicize this technology, there is not much external technical information.
　　
Foveon X3: foveon X3 is a CMOS image sensor technology that provides three primary colors in a single pixel. Unlike traditional single-pixel single-color CCD/CMOS sensor technology, X3 is similar to Silver-salt color film, and is vertically stacked by three layers of photosensitive elements. It provides a richer color reduction degree and avoids the color interference that is unique to traditional sensors using the Bayer pattern. In addition, because each pixel provides complete three primary color information, the process of combining color signals into image files is much simpler, reducing the computing requirements for image processing. The X3 image sensor using cmos semiconductor technology consumes less power than traditional CCD.
　　
　　
Figure 3: How foveon X3 works: different colors are absorbed at different depths of a silicon wafer.
　　
Ii. Lens parameters
　　
Any camera lens is crucial, and digital cameras are no exception. Speaking of the camera, we should first talk about the background of the current digital camera manufacturers. One is the manufacturers that originally produced cameras, such as Nikon, Canon, Minolta, Pentax, and Olympus, another type is consumer electronics manufacturers, such as Sony, Panasonic, Casio, and Samsung. The first category of manufacturers generally use their own lenses. The latter category uses lenses produced by other manufacturers, for example, Sony Uses German Zeiss lenses, panasonic uses Lycra from Germany, Samsung uses Schneider from Germany, and Casio uses Pentax from Japan. These are all well-known names. If you are not familiar with them, it doesn't matter. Here we will give you a brief introduction:
　　
Chinese name English name Nationality
Nikon nikkor * Japan
Canon canon Japan
Minolta Japan
Pentax Japan
Olympus Japan
Sigma Japan
Karl chase Carl Zeiss Germany
Lycra Germany
Sri Lanka Schneider Germany
　　
　　
Table 2: well-known shot Manufacturers
　　
* Nikon's body and lens use different trademarks. The body uses Nikon, and the lens uses nikkor.
　　
These are all famous brands, so consumers can purchase them with confidence.
　　
The main parameters of the lens include aperture, shutter, focal length, zoom, and shortest focus distance.
　　
Aperture
　　
Aperture is the unit that represents the amount of light that the lens uses per unit of time. We can see a circular movable "Door" from the lens. This is the aperture. By opening and closing the door, we can control the amount of light entering the camera. Common examples include f2.8, F4, f5.6, F8, and F11. The smaller the value, the larger the aperture, that is, the larger the door is opened. The maximum aperture of a common digital camera is f2.8, f1.8, and f2.0. The minimum aperture is f8.
　　
Focal Length
　　
The focal length refers to the distance from the lens to the lens focus (CCD or CMOS on a digital camera. To put it bluntly, the larger the focal length, the farther it looks.
　　
Zoom Lens
　　
As the name suggests, a zoom lens is a lens with a focal length that can be adjusted. Currently, most digital cameras use zoom lenses, and most of them use triple zoom.
　　
Shortest focus distance
　　
You can take a close picture of an object. This is the strength of a digital camera. Most digital cameras can reach 3-5 cm, and some can even reach 1 cm or less. This is useful for macro shooting.
　　
Depth of field
　　
Clear Distance before and after focus. We can often see that some images are clear only when the subject is being taken, and the rest are blurred. This is why the depth of field is small. Small depth of depth is often used to highlight the main body, large aperture is often used to create a small depth of depth effect, 4, large aperture causes a small depth of depth, so that only the lotus nearby is clear after the lotus leaves become blurred, highlight the subject.
　　
Shutter
　　
The shutter of most cameras is on the body, but we put it here for clarity. The shutter speed of most digital cameras ranges from several seconds to 1‰ seconds, and advanced machines can reach two thousand and four or even eight thousand copies to one second, high-speed shutter helps photographers capture moving objects. It is worth noting that the marked 2, 5, 125, and 500 on the camera are actually 1/2, 1/5, 1/125, and 1/500 seconds.
　　
Digital cameras are getting closer and closer to us, and people begin to learn more about digital cameras. I believe that every user has this feeling. when buying a digital camera, I don't know much about the many technical terms in the promotional materials, in more cases, I 'd like to hear the salesperson explain which one is better or better! In addition, many users do not have any research on photography, so it is more necessary to let everyone know about some technical terms about cameras. When purchasing digital cameras, let yourself be a clear consumer and select your favorite product!
　　
Basic knowledge:
　　
Valid records: The number of valid records that an image sensor receives from an optical lens. Valid records indicate the records of an image sensor, which are directly reflected in the final output data of a static image.
Interpolation is a method to increase the pixel size of an image without generating pixels. Based on the color of the surrounding pixels, the color of the lost pixel is calculated using mathematical formulas. Some cameras use interpolation to artificially increase the image resolution system.
Sensitivity (ISO): It is generally used to measure the amount of light required by the film for accurate exposure. The sensitivity is generally represented by an ISO value. This value increases the film's sensitivity to light, so that it can be shot in different light. To make it easier for digital camera users to understand, digital camera manufacturers generally convert the sensitivity (or light sensitivity) of CCD to the sensitivity value of traditional films.
　　
　　
　　
White Balance: The color is essentially an explanation of the light. In normal light, it looks like a white color. In a dark light, it may not look white, there is also "white" under the fluorescent lamp is also "non-white ". White Balance is a technology that defines "white" as "white" regardless of the ambient light.
Digital zoom: through the calculation of the Program on the body and the coordination of the optical system, we can make a local zoom of the subject, and simulate the optical zoom effect by interpolation. It works in a way similar to how we zoom in a part of the image on a computer. The difference is that "digital zoom" is done directly on the CCD during the shooting process. Specifically, "digital zoom" is only a crop tool because it can cut out part of the image-this part is out of the field of view when using a long focal length lens, only the selected local area is stored.
Optical zoom: for digital cameras, "optical zoom" does not change the image size or resolution, and the number of records used to describe the image remains unchanged, this is the fundamental difference between "optical zoom" and "digital zoom", embodied in the image, that is, the image quality will be different.
Exposure Compensation: After the camera detects the light, it can be adjusted in different levels to make the image approximate to the actual light. This is the exposure compensation.
Manual exposure: allows you to freely control the combination of aperture and shutter. the shutter speed display in the viewfinder allows you to adjust the aperture or Shutter for correct exposure. If necessary, you can increase or decrease the exposure to create a special effect.
Lens focal length: refers to the distance from the focal point to the lens after parallel light passes through the lens. Basically, if the position of the subject remains unchanged, the focal length of the lens is directly proportional to the magnification of the object.
Aperture: the number of aperture sizes at all levels is called the aperture coefficient, expressed as f/. It is the reciprocal of the relative aperture, for example, 5. the aperture coefficient is f/3.5 or 3.5, the smaller the aperture, the less incoming light. for each level of difference, the number difference is the square root of 2, for example: 1. L.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22 ...... the aperture coefficient is often said to be an aperture.
TTL: through the lens (through the lens) is a single lens reflector.
AF (Auto Focus) Auto Focus: auto focus can be set to active or passive based on the control principle. Active auto-focus emits a ray (usually infrared) from the camera, determines the distance between the subject based on the reflected ray signal, and then automatically adjusts the lens to enable auto-focus. Passive focus is a bit of a bionic taste. It analyzes whether the imaging of an object has been focused and is accurate. However, the technology is complicated and costly, and it is difficult to focus accurately under Low Illumination Conditions, it is mostly used for high-end professional cameras. Some highly intelligent cameras can also lock the motion of the subject or even eye-controlled focus.
　　
　　
　　
AE (Auto expose) Automatic Exposure: Automatic Exposure means that the camera automatically determines the exposure according to the light conditions. There are two fundamental Optical Metering principles: incident type and reflection type. The incident type is to measure the brightness of the light emitted to the camera to determine the exposure combination. Reflection is an ideal method for measuring the actual brightness of the subject, that is, the brightness of the imaging to determine the exposure combination. Based on the metering method, you can use multiple metering methods such as automatic exposure, automatic central focus exposure, and automatic multi-point balance exposure. Each method has its own advantages and disadvantages and is suitable for different lighting conditions or shooting purposes. The control process can be divided into Aperture priority, shutter priority, hybrid priority, program control, and reservation mode.
Aperture Priority: Determine the Aperture Used first, and then the camera determines the appropriate shutter speed based on the calculated exposure. This method is suitable for scenarios where the depth of field needs to be specified or when the ratio of light needs to be adjusted with the flashlight;
Speed first: Determine the shutter speed first, let the camera select the appropriate aperture size, applicable to the shooting body; mixing priority is to make up for the single priority and first determine the aperture or shutter range, then the camera determines the combination of exposures.
Program Control: allows the camera to be exposed according to a preset control procedure.
Reservation mode: The manufacturer preset reasonable exposure parameters for shooting based on several common lighting conditions.
AWB: (Automatic white balance) automatically adjusts the color temperature based on the light source of the shooting place.
Color temperature: the different color scales of the things that are taken due to different types of light sources.
　　
ISAPS technology: (Chinese name: intelligent scene analysis based on photographic space) is a unique technology of Canon. It uses Statistical Analysis Technology to Improve the Performance of AF, AE, and AWB. By analyzing the user's photo frequency and parameters, canon can set the focal length, focal distance, scene brightness, and other factors. Relying on different combinations of statistical frequencies and advanced prediction algorithms in various situations, canon digital cameras can more accurately and effectively optimize AF, AE, and AEB in any scenario. (Canon proprietary technology)
Broadband digital technology: Make full use of the memory card space to record activity images and sounds to the maximum extent. (Olympus proprietary technology)
Multi-Point intelligent autofocus: (Multi-Point AIAF) wide-area autofocus automatically selects one or more focal points for the subject in the context box. Work with ISAPS technology to achieve faster and more accurate auto focus in multiple shooting environments. (Canon proprietary technology)
　　
　　
　　
Flexizone AF/AE: flexizone AF/AE function. Photographers can freely move their focus points within the range of the picture frame. when the subject is not in the center of the picture, you do not need to repeat the picture. When you select a spot metering point, you can select the focal point in the context box to adapt to the complex lighting environment to a greater extent. (Canon proprietary technology)
Digital ESP metering system: select an appropriate exposure mode in different environments (or even when the light conditions are very bad. It ensures that accurate exposure results can be achieved in the case of backlight or high contrast. (Olympus proprietary technology)
Point metering system: you can measure the light at up to 8 points on the same screen to read a specific area of the photo to get the expected exact effect and use the exposure lock.
Center weighted average light measurement: based on the average light measurement, images in the center or near area are calculated based on different weighting coefficients. The center weight is the largest, and the center is the edge of the image, the smaller the weight. The final value is the metering value.
　　
Storage Medium:
　　
Cfcard: cfcard was first launched by SanDisk in 1994. This storage media uses Flash technology to permanently store information without power. Fast, light, and only the size of the matchbox.
　　
Xdcard: (extreme digital, Express Card) is jointly developed and held by Olympus, Fuji and Toshiba. Olympus and Fuji saw that smka had not kept up with the trend and technology, so they joined hands to launch a more sophisticated and advanced xdcard.
Mmccard: multimediacard, a multi-media card developed by SanDisk and Siemens, Germany. It can be used to carry phones, digital cameras, and digital cameras, MP3 and other digital products. It has the characteristics of small and lightweight, and is resistant to impact. It can read and write records 0.3 million times repeatedly.
SD card: Secure Digital card, a secure digital card developed by Panasonic, Toshiba, and SanDisk, in particular, the security and other features of the multi-functional memory card. It has an additional ID authentication function (sdmi Specification) for data copyright protection than the mmccard ). Currently, it is mostly used for MP3, digital cameras, e-books, micro-computers, AV equipment, etc. The read/write speed is 4 times faster than that of the mmccard, up to 2 MB/second. At the same time, it is compatible with mmccards, and most SD card plug-ins support mmccards.
Sony memory stick (memory stick): Sony memory stick is an ultra-micro volume (gum size) developed by Sony in July 1997 together with Casio, Fujitsu, Olympus, Sanyo and sharp) integrated circuit digital storage medium.
　　
　　
　　
Image Storage Format:
　　
EXIF format: (exchangeable image file-Abbreviation of interchangeable image files), which is specially set for digital camera photos. This format records attributes of digital photos.
Exif2.2: An improved digital camera file format that contains various shooting information required for optimal printing.
Dpof (digital print order format) Format: it is a standard format of printed and ordered materials, when a photo is printed by a personal photo camera or printer or by a professional photo printing service center, the ordering requirements of the records are automatically delivered to the output device.
DCF format: a unified record format for digital cameras. It is the abbreviation of design rule of camera file system in the jeida specification of the Japanese electronics industry revitalization Association (jeida) to facilitate the use of profile files between devices.
Raw format: Raw record data on the sensor (CCD or CMOS) is directly read, that is, the data has not been processed by exposure compensation, color balance, Gamma adjustment, and so on. To put it bluntly, it is an image that has not been taken out by any person as a factor and is not compressed. Therefore, professional photographers can use specialized software, such as Photoshop, to compensate for exposure, color balance, and gamma adjustments.
Tiff: Short for Tagged Image File Format. Other bit map file files may record information about preview images and large-size content. Because its software package can ignore the information that cannot be read, it can be said that its file form is relatively independent of the platform.