Introduce some simple digital photography terms.

"Pixel" consists of letters of the words "picture" and "element", which is the unit used to calculate digital images. Just like photos, digital images have continuous shadows. If you enlarge the image several times, you will find that these continuous tones are actually composed of many small squares with similar colors, which are the smallest unit "pixels" that make up the image. This smallest graphic unit can usually display a coloring point on the screen. The higher the pixel, the richer the sample and the more realistic the color is. Pixel is usually considered as the smallest complete sample of an image. This definition is very relevant to the context. For example, we can say that pixels in a visible image (such as a printed page) are pixels represented by electronic signals, pixels represented by numbers, pixels on a display or pixels in a digital camera (photosensitive element). Many other examples can be added to this list. Depending on the context, there will be some more accurate synonyms, such as pixels, sampling points, bytes, bits, dots, spots, supersets, triples, edge sets, windows and so on. We can also discuss pixels abstractly, especially when using pixels as a measure of resolution, such as 2400 pixels per inch (ppi) or 640 pixels per line. Dots are sometimes used to represent pixels, especially computer marketers, so ppi is sometimes written as DPI (dots per inch). The more pixels used to represent an image, the closer the result is to the original image. Although there is a more specific definition of resolution, the number of pixels in an image is sometimes called image resolution. Pixels can be represented by a number, such as a "3 megapixel" digital camera with a rated pixel of 3 million, or by a pair of numbers, such as a "640 × 480 display" with 640 pixels in the horizontal direction and 480 pixels in the vertical direction (just like a VGA display), so its total number is 640× 480 = 307,200 pixels. The color sampling points of digital images (such as JPG files commonly used in web pages) are also called pixels. Depending on the computer monitor, these pixels may not have a one-to-one correspondence with the screen pixels. In this obviously different area, the points in the image file are closer to the texture elements. In computer programming, an image composed of pixels is called a bitmap or raster image. The word grating comes from analog TV technology. Bitmap images can be used to encode digital images and some types of computer-generated art.

Pixel is the most important index to measure a digital camera. Pixel refers to the resolution of a digital camera. Depending on the number of photosensitive elements on the photoelectric sensor in the camera, 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 is determined by pixels. The larger the pixel, the greater the resolution of the photo, and the larger the print size without reducing the print quality. Early digital cameras were all below 6.5438+0 million pixels. Since the second half of 1999, 2-megapixel products have gradually become the mainstream of the market. (joke, now mobile phones are generally 2 million pixels, and domestic cameras are generally about 5 to 6 million pixels. Otherwise, you might as well take pictures with your mobile phone. At present, the development trend of digital cameras is that pixels, like the CPU frequency of a PC, have an increasing momentum. In fact, from the perspective of market classification, for popular products, considering the factor of cost performance, the bigger the pixel, the better. After all, a 2-megapixel product can meet most applications of ordinary consumers. For this reason, while most manufacturers pursue high-end digital cameras with high pixels, the largest output at present is still the popular mega-pixel products. Professional digital cameras have products with more than 1 100 million pixels. With the progress of CCD (imaging chip) manufacturing technology and the further reduction of cost, 3 million pixel products will soon become the mainstream of the consumer market. In addition, it is worth consumers' attention that the current digital camera products are nominally divided into CCD pixels and software-optimized pixels, and the latter is much higher than the former. For example, a brand of Volkswagen digital camera has 2.3 million CCD pixels, while the pixels after software optimization can reach 3.3 million.

When you say microphotography, you mean macro photography, right?

Macro photography is a relatively large category in photography activities. It can be said that most people engaged in photography have been exposed to macro photography to some extent.

Macro photography is not mysterious, but some photographers have an elusive feeling about this kind of photography, mainly thinking that macro photography is an alternative way after engaging in ordinary photography. In fact, macro photography is an extension of ordinary photography, and its working mechanism is the same as that of ordinary photography, and it must abide by the basic laws of optics.

Macro photography also has its particularity, so it involves many accessories. How to use these accessories flexibly is the starting point of this paper.

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In photography, a concept of magnification is involved, which is related to the reproduction ratio of the image. The copy ratio is the numerical relationship between the actual size of the subject and the size of the image, which is usually expressed by the numbers on both sides of the colon:

[Image Size]: [Actual size of object]

Generally, any number on the left or right is classified as 1, which is generally expressed as: 1: X/X: 1. The former means that [the actual size of the subject] is x times the size of the image; The latter means that [image size] is x times the actual size of the object.

For example, it is labeled as:

1: 10: indicates that the actual size of the subject is 10 times the size of the image, or the size of the image is110;

1: 1: indicates that the actual size of the subject is equal to the image size.

According to the magnification, macro photography can be subdivided into close-range photography and ultra-close-range photography. There is no strict definition, but the general definition is:

Close-range photography: the magnification is1:10 ~1:1;

Ultra-close photography:1:1~ 6:1;

Beyond this magnification, it begins to enter the scope of photomicrography.

Another focus of the lens is zoom capability, including optical zoom and digital zoom. Although both of them are helpful to enlarge distant objects in telephoto shooting, only optical zoom can support adding more pixels after the main body of the image is imaged, making the main body not only larger but also relatively clearer. Usually, the larger the zoom factor, the more suitable for telephoto shooting. Optical zoom, like traditional camera design, depends on the focal length of the lens, so the resolution and image quality will not change. Digital zoom can only reduce the size of the original image and make the image larger on the LCD screen, but it does not help to clarify the details. So when buying a digital camera, we often suggest that you pay attention to the multiple of optical zoom. At present, mid-range cameras generally have about 3 times optical zoom, but there are also products with long zoom function, such as 10 times optical zoom models.

Another focus of the lens is zoom capability, including optical zoom and digital zoom. Although both of them are helpful to enlarge distant objects in telephoto shooting, only optical zoom can support adding more pixels after the main body of the image is imaged, making the main body not only larger but also relatively clearer. Usually, the larger the zoom factor, the more suitable for telephoto shooting. Optical zoom, like traditional camera design, depends on the focal length of the lens, so the resolution and image quality will not change. Digital zoom can only reduce the size of the original image and make the image larger on the LCD screen, but it does not help to clarify the details. So when buying a digital camera, we often suggest that you pay attention to the multiple of optical zoom. At present, mid-range cameras generally have about 3 times optical zoom, but there are also products with long zoom function, such as 10 times optical zoom models.

Another focus of the lens is zoom capability, including optical zoom and digital zoom. Although both of them are helpful to enlarge distant objects in telephoto shooting, only optical zoom can support adding more pixels after the main body of the image is imaged, making the main body not only larger but also relatively clearer. Usually, the larger the zoom factor, the more suitable for telephoto shooting. Optical zoom, like traditional camera design, depends on the focal length of the lens, so the resolution and image quality will not change. Digital zoom can only reduce the size of the original image and make the image larger on the LCD screen, but it does not help to clarify the details. So when buying a digital camera, we often suggest that you pay attention to the multiple of optical zoom. At present, mid-range cameras generally have about 3 times optical zoom, but there are also products with long zoom function, such as 10 times optical zoom models.

The noise of digital camera, also called noise, mainly refers to the rough part of the image when CCD(CMOS) receives and outputs light as the received signal, and also refers to the foreign pixels that should not appear in the image, usually caused by electronic interference. It looks like the image has been dyed and covered with some tiny rough spots. The digital photos we usually take may not be noticed if we use a personal computer to reduce the high-quality images and then look at them. However, if the original image is enlarged, there will be a color (pseudo-color) that did not exist originally, and this pseudo-color is image noise.

In addition to noise, there is another phenomenon that is easily confused with noise, which is a bad point. Under the same digital camera setting conditions, if the clutter always appears in the same position in the captured image, it shows that this digital camera has bad points. General manufacturers have regulations on the number of bad spots. If the number of bad spots exceeds the specified number, you can replace the camera with dealers and manufacturers. If the noise points do not appear in the same position, it means that these noise points are due to the noise formed during use.

Thermal pixel: both CCD and CMOS photosensitive elements have thermal stability problems, which are related to imaging quality and temperature. If the machine temperature rises and the noise signal is too strong, it will form mottled spots where the picture should not be. These points are what we call dry points. Various brands and models of cameras have different ability to control dry spots. Cameras of the same model also have certain individual differences, and some cameras have the function of reducing dry spots. But the problem of dry spot is a problem that all DC can't completely overcome now (improving the sensitivity (ISO), especially when the exposure time is long or the camera temperature rises).

A shutter is a device that blocks light from entering a camera lens. Generally speaking, the longer the shutter time range, the better. Low seconds is suitable for shooting moving objects, so a camera emphasizes that the shutter can reach116000 seconds at the earliest, which can easily capture fast moving targets. However, when shooting traffic at night, the shutter time will be lengthened, and the silky water flow effect in ordinary photos can only be photographed with a slow shutter. As for the common B shutter function of monocular cameras, although you can freely decide the exposure time and have high shooting flexibility, most consumer digital cameras can't support it at present, and can provide the default values of slower speeds such as 2 seconds, 8 seconds, 16 seconds at most. Together with the aperture, it is called an important part of determining the exposure time. There are lens shutters installed in the lens part, electronic shutters that control the opening and closing time by electronic means, focal plane shutters close to the film, etc. Taking a single lens reflex camera as an example, its advantages and disadvantages are compared. The lens shutter has the convenience of frequency flash synchronization, the shutter vibration is small, and it is expensive to replace the lens. The focal plane shutter is just the opposite. Electronic shutters, especially slow shutters, have good accuracy. The shutter speed of aperture priority camera can be adjusted at will.

Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens, usually in the lens. We use the f value to represent the aperture size. For the manufactured lens, we can't change the diameter of the lens at will, but we can control the luminous flux of the lens by adding a polygon or circular aperture grating with variable area inside the lens. This device is called an aperture.

Aperture f value = lens focal length/lens aperture diameter

As can be seen from the above formula, to achieve the same aperture f value, the aperture of a long focal length lens is larger than that of a short focal length lens. The complete series of aperture values is as follows:

f 1，f 1.4，f2，f2.8，f4，f5.6，f8，f 1 1，f 16，f22，f32，f44，f64

It is worth mentioning here that the smaller the f value of the aperture, the more light enters in the same unit time, and the light entering amount of the upper level is exactly twice that of the lower level. For example, if the aperture is adjusted from f8 to f5.6, the amount of light entering will double. We also say that the aperture is enlarged by one level. For consumer digital cameras, the aperture f value is often between f2.8-f 16. In addition, many digital cameras can adjust the aperture by 1/3.

The English name of Aperture is aperture. Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens. It is also an extremely important index parameter of the camera, usually in the lens. Its size determines how much light enters the photosensitive element through the lens. We use the f value to represent the aperture size. Aperture f value = lens focal length/lens aperture diameter According to the above formula, to achieve the same aperture f value, the aperture of a long focal length lens is larger than that of a short focal length lens.

Aperture and shutter take precedence.

In addition to providing automatic mode, advanced digital cameras usually have two options: aperture priority and shutter priority, so that you can decide a certain aperture value or a certain shutter value on some occasions, and then match the appropriate shutter or aperture respectively to present different depth of field (sharpness) or effects.

Aperture priority exposure mode

After we decide the aperture f value ourselves, the camera metering system will automatically choose the appropriate shutter speed (which can be an accurate stepless shutter speed) according to the light conditions at that time. A digital camera with an exposure mode dial usually engraves the letter "A" on the dial to indicate the aperture priority mode (see Figure 4). Aperture prerequisite mode is suitable for photography that emphasizes the depth of field effect.

Because the focal length of digital camera is much shorter than that of traditional camera and the aperture of lens is small, it is difficult to produce narrow depth of field. Some digital cameras have a special portrait exposure mode, using built-in programs to blur the foreground and background.

Aperture type

Fixed aperture. The simplest camera only has a fixed aperture with a round hole.

Walter Hauser aperture. The initial variable aperture is just a series of circular holes with different sizes, arranged around a disk with a central axis; Rotating the disc can move the circular hole with appropriate size to the optical axis, thus controlling the aperture. John Vaught Hauser invented this kind of aperture in the middle of19th century.

The cat's eye aperture consists of a metal plate with an oval or diamond hole in the middle, which is divided into two parts. Two metal sheets with semi-elliptical or semi-diamond holes are arranged in opposite rows and moved relative to each other to form a cat's eye aperture. Cat's eye aperture is mostly used for simple cameras.

Iris-type aperture is composed of a plurality of overlapping arc-shaped thin metal blades, and the size of the central circular hole can be changed by the clutch of the blades. Some cameras can change the aperture of the diaphragm by rotating the ring on the lens barrel, while others automatically change the aperture of the diaphragm by controlling the micro-motor through the microprocessor chip. There can be as many as eighteen arc-shaped thin metal blades. The more arc-shaped thin metal blades, the closer the aperture is to a circle. By designing the shape of thin metal blades by computer, a nearly circular aperture can be obtained with only 7 thin metal blades.

Instantaneous aperture

The aperture of a SLR camera is instantaneous, and only when the shutter is opened will the aperture be reduced to a predetermined size. Usually the aperture is at the maximum position.

Double shutter aperture

The aperture of some simple cameras has shutter function. Most of these double shutter apertures are cat's eye apertures with two blades. Different from the simple cat's eye aperture, the double shutter aperture is usually completely closed: at the moment when the shutter is pressed, the double shutter aperture opens to a predetermined aperture, and then it is closed immediately after maintaining the aperture for a predetermined shutter opening time; In this way, the aperture also acts as a shutter.

aperture size

The smaller the value after f, the larger the aperture. The function of the aperture is to determine the amount of light entering the lens. The larger the aperture value, the more light enters. On the contrary, the smaller. Simply put, under the condition of constant shutter, the larger the aperture, the more light enters and the brighter the picture; The smaller the aperture, the darker the picture.

Although they are all copied and pasted, it doesn't mean that I don't know, but I dedicate the most professional explanation to the questioner. Can you guarantee that your summary is correct? What's more, copying and pasting takes time.