When buying a digital camera, many users will ask, what is digital zoom and what is optical zoom? Below, we will use the chart to illustrate.
Optical zoom is achieved by changing the position of lens, object and focus. When the image plane moves in the horizontal direction, as shown below, the visual field and focal length will change, and the farther scenery will become clearer, making people feel that the object is moving forward.
Obviously, there are two ways to change the perspective. One is to change the focal length of the lens. In photography, this is optical zoom. The focal length of the zoom lens is changed by changing the relative position of the lens. The other is to change the size of the imaging plane, that is, the diagonal length of the imaging plane. In today's digital photography, this is called digital zoom. In fact, digital zoom does not change the focal length of the lens, but changes the viewing angle by changing the diagonal of the imaging plane, thus producing an effect equivalent to the focal length change of the lens.
Therefore, we can see that some digital cameras with long lenses have more room for moving the internal lens and photoreceptor, so the zoom factor is also larger. We see that some ultra-thin digital cameras on the market generally have no optical zoom function, because the roots in the fuselage are not allowed to move the photosensitive devices, while Sony F828, Fuji S7000 and other "long lens" digital cameras have optical zoom functions as high as 5 or 6 times.
At present, the optical zoom multiple of digital cameras is mostly between 2 and 5 times, which can zoom objects beyond 10 meter to 5-3 meters; There are also some digital cameras whose optical zoom effect is 10 times. The optical zoom factor of home camcorder is 10 ~22 times, and it can clearly shoot things 70 meters away. Using a magnifying glass can increase the optical zoom factor of the camera. If the optical zoom factor is not enough, we can add a zoom lens in front of the lens. The calculation method is as follows: A 2-fold zoom lens is set on a 4-fold optical zoom digital camera, and then the optical zoom multiple of this digital camera will be changed from the original 1, 2,3,4 times to 2,4,6 times and 8 times, that is, it is obtained by multiplying the zoom lens multiple and the optical zoom multiple.
Digital Zoom, also known as digital zoom, is called digital zoom in English. Digital zoom is to enlarge the area of each pixel in the picture through the processor in the digital camera, so as to achieve the purpose of enlargement. This technology is like enlarging the area of a picture with image processing software, but the program is executed in a digital camera. Some pixels on the original CCD image sensor are enlarged by interpolation, and the pixels on the CCD image sensor are enlarged to the whole picture by interpolation algorithm.
Different from optical zoom, digital zoom is the change of the vertical direction of the photosensitive device, which gives people a zoom effect. The smaller the area on the photosensitive device, the user can only see part of the scene visually. However, because the focal length has not changed, the picture quality is worse than normal.
Through digital zoom, the shot scene is enlarged, but its definition will be reduced to some extent, so the practical significance of digital zoom is not great. However, Sony's original "intelligent digital zoom" is said to be an advanced technology that can keep the image clear after digital zoom.
The total zoom number of a digital camera is calculated as follows: For example, the optical zoom of Sony F7 17 is 5 times, while the digital zoom is 2 times, so the maximum zoom number is 10 times. Digital zoom in digital cameras can usually be turned off. In addition, there is a brand-new and unique Sony intelligent zoom function, which can enlarge the zoom shooting without enlarging the particles, so that the enlarged image can maintain the original detail quality. Intelligent zoom provides different degrees of enhanced zoom function according to the choice of different image sizes. Unlike digital zoom, smart zoom can maintain the same image quality as the original image.
At present, the digital zoom of digital cameras is generally about 6 times, and the digital zoom of cameras is about 44 times to 600 times. In actual use, 40 times is enough. Because too large digital zoom will seriously damage the image, and sometimes even because the magnification is too high, it is impossible to distinguish the shot picture. If the zoom factor is not enough, we can add a zoom lens in front of the lens. The calculation method is as follows: A 2-fold zoom lens is set on a 4-fold optical zoom digital camera, and then the optical zoom multiple of this digital camera will be changed from the original 1, 2,3,4 times to 2,4,6 times and 8 times, that is, it is obtained by multiplying the zoom lens multiple and the optical zoom multiple.
Interested parties can take a look at the following detailed introduction.
1. What are the imaging devices of digital cameras?
Digital cameras use electronic components to image rather than film-this is the most essential difference between digital cameras and traditional cameras. Imaging devices of digital cameras are mainly divided into two categories:
CCD-abbreviation of English Charge Coupled Device, Chinese name is "Charge Coupled Device".
Cmos-abbreviation of English complementary metal-oxide semiconductor, Chinese name is "complementary metal-oxide semiconductor".
2. Charge Coupled Devices
1)CCD is the mainstream imaging device at present, which is mainly divided into:
(1)R-G-B primary CCD: This is the most widely used CCD in digital cameras.
(2)C-Y-G-M complementary color CCD: Some Nikon digital cameras used this complementary color CCD earlier.
(3)R-G-B-E four-color CCD: This is the latest CCD released by Sony, which has one more E (Emerald) color than RGB primary CCD.
2) Super CCD: It is a patented technology of Fuji Company in Japan. Its Chinese name is super CCD, which evolved from CCD and has now developed to the fourth generation.
3)CMOS: As an imaging device of digital camera, it has not appeared for a long time, but it has developed very rapidly and is likely to compete with CCD. There is no essential difference between the pixel arrangement in its basic structure and the R-G-B primary color CCD. Canon is the main supporter of the CMO camp.
4)Foveon X3: Its essence is also CMOS, but its structure is very different from that of CMOS. At present, the highest pixel reaches 5 million.
3. How does a digital camera image?
A) light is projected onto the surface layer of a photosensitive element through a lens;
B) the light is decomposed into different colors by the surface filter of the photosensitive element;
C) The colored light is induced by the photosensitive unit corresponding to each filter to generate analog current signals with different intensities, and then these signals are collected by the circuit of the photosensitive element;
D) Analog signals are converted into digital signals by digital-to-analog converters, and then these signals are processed by DSP and restored into digital images;
E) transmitting the digital image to a memory card for storage.
4. What are the characteristics of 4.CCD?
The CCD technology is mature and the imaging quality is good. After all, it is the most widely used imaging element now, but it also has shortcomings:
1) consumes a lot of power. Early digital cameras were known as "electric tigers", and one of the main reasons came from CCD. Although the use of low-energy components such as low-temperature polysilicon display screen reduces the power consumption of the camera to a certain extent, CCD is still a big power consumer of digital cameras-CCD keeps working at any time after the digital camera is turned on, which consumes a lot of electricity unnecessarily.
2) The process is complicated and the cost is high. The complex structure of CCD determines the complexity of its manufacturing process, so so far, only a few electronic giants can produce CCD.
3) pixel promotion is difficult. The first two shortcomings of CCD also directly lead to this shortcoming. There are only two ways to improve CCD pixels: one is to increase the CCD area by keeping the unit area of photosensitive elements unchanged, and integrate more photosensitive elements on a large CCD. However, this method will lead to low yield of CCD, high manufacturing cost and high power consumption, which is unrealistic in the civil field; Second, reduce the unit area of photosensitive elements and integrate more photosensitive elements on the existing horizontal CCD area. However, this method will reduce the unit photosensitive area of photosensitive elements, reduce the overall sensitivity and dynamic range of CCD and affect the image quality.
5. What are the characteristics of 5.CMOS?
In recent years, the development speed of CMOS is quite good, and it has great potential to compete with CCD-even the top DSLR (Single Lens Reflective Digital Camera), Kodak DCS/KOOC-0/4N and Canon EOS/KOOC-0/DS all use CMOS imaging.
Compared with CCD, CMOS has two outstanding advantages:
1) has low price and simple manufacturing process. CMOS can be produced by ordinary semiconductor production line, unlike CCD, which requires special production process, so the manufacturing cost is much lower. Moreover, the size and output of CMOS are not as limited as CCD.
2) Low power consumption. Although there is little difference between CMOS filter layout and CCD, the circuit structure of photosensitive unit is very different. Each photosensitive element of CMOS has an independent charge/voltage conversion circuit, which can independently amplify and output the electrical signal after photoelectric conversion-this is much faster than CCD collecting all the signals and then amplifying the output. Moreover, the photosensitive element of CMOS only works during photosensitive imaging, so it saves electricity compared with CCD. However, CMOS also has disadvantages. If there are many imaging actions when using a digital camera, CMOS will heat up due to the changeable current when it is started frequently, which will lead to disorder and affect the image quality.
6. How to understand the basic parameters of imaging elements?
Imaging element is the core of digital camera, so it is necessary to know some important parameters correctly, which will bring a lot of help to understand the basic performance of digital camera and how to buy digital camera.
Total pixels-Total pixels refer to the number of imaging units on the imaging element of a digital camera. A CCD with a total pixel of 5.24 million means that 5.24 million imaging units are integrated on it. The total number of pixels is basically used to mark the performance of digital codes one by one.
Effective pixel-When a digital camera is imaging, the edge of the photosensitive element will be blurred due to the diffraction of light. In order to ensure the imaging quality, this part of the imaging on the photosensitive element will be discarded, so the photosensitive unit cannot use 100%. The utilized pixel, that is, the final image, becomes an effective pixel.
Size-refers to the diagonal length of the photosensitive element, usually in inches. Common ones are11.8 inch, 1/2.7 inch, 2/3 inch and so on. Generally speaking, the larger the size of the photosensitive element, the better the performance and imaging effect of the element. In addition, the photosensitive elements of digital cameras generally adopt the aspect ratio of 4: 3, especially 3: 2.
ISO- refers to the sensitivity of photosensitive elements to light induction. The larger the value, the higher the sensitivity. Common values are 50, 80, 100, 160, 200, 400, etc. At present, the highest ISO value of photosensitive elements of digital cameras can reach 3200. It should be noted that although a high ISO value can improve the imaging quality of a digital camera in a dark environment, the higher the ISO value, the more obvious the impact on the image quality and the more noise there will be.
7. What is the conversion relationship between the print size of digital photos and the resolution of photos?
What is the conversion relationship between the print size of digital photos and the resolution of photos? It can be expressed by an expression:
The number of pixels on the long side of a digital photo ÷ photo output accuracy = the size of the output photo.
Take a 5 megapixel digital camera as an example. The maximum resolution of the output photos is 2560× 1920, and the effective pixels are 2560×1920 = 4915000, which is about 4.92 million. If the print output accuracy is 300 dpi (dpi-dots/inch), you can output 2560÷300=8.5 inches, that is, you can output 8 inches of photos; If the digital photos are developed digitally, according to the minimum printing accuracy of digital printing 150DPI, 2560÷ 150= 17 inches can be output, that is, photos with 17 inches can be output. In other words, a 2-megapixel digital camera can generally achieve a photo resolution of 1600× 1300. If you print digitally with the lowest printing accuracy of 150DPI, you can get a photo of 10 inch, which is enough for ordinary families.
8. What is an aperture?
Aperture is a parameter used to express the luminous flux of lens, and it is also an important index to measure the quality of lens. Generally, we use the maximum aperture value of the lens to represent it. Aperture is generally expressed as "F+ number", which is based on the ratio of lens focal length to lens effective aperture, that is, the larger the lens effective aperture, the smaller the value after f, which means the larger the aperture. Generally, the numerical value of the aperture is increasing or decreasing in geometric series, such as F 1, F 1.4, F2.8 A lens with a large aperture is called a fast lens. For example, in a poor light environment, the lens with the maximum aperture of F2.8 needs only a shutter of 1/30 seconds to get a proper exposure because of its large luminous flux, while the lens with the maximum aperture of F4 can't. So generally speaking, the larger the aperture, the higher the lens quality. In addition, a parameter related to the aperture is the aperture of the lens. The aperture of a lens is the diameter of the lens. The larger the aperture of the lens, the more light it passes, the better the imaging, and of course, the more expensive it is. The aperture is expressed in mm, and the significance of understanding this parameter is that when you want to choose accessories such as UV mirror, color filter or external lens for the lens in the future, you must buy corresponding accessories according to the aperture of the lens.
9. How to identify the various values marked on the lens?
Take the lens of Canon G5 as an example to explain how to read the values marked on the lens.
Canon zoom lens-indicates that the camera uses Canon zoom lens.
7.2-24.8mm—— It means that the actual focal length of the zoom lens used in this camera is 7.2mm-24.8mm, which is 35- 140 when converted into a traditional 135 film camera.
1:2.0-3.0- indicates that the maximum aperture of the wide-angle lens is F2.0 and that of the telephoto lens is F3.0. ..
& amp52mm—— It means that the diameter of the lens interface is 52mm. That is to say, if the lens wants to use external filters such as UV mirrors, it must use an external lens with a diameter of 49 mm. ..
10, what are the common lens brands on cameras?
There are many brands of lenses used in digital cameras. Knowing these lens brands is helpful for understanding and buying digital cameras.
Canon lens: Canon is a traditional optical manufacturer. This company's EF series lenses in the field of traditional cameras, especially the red circle lens representing aristocratic descent, have always been the dream of many photographers. Therefore, with years of accumulated experience in the field of traditional lens manufacturing, Canon's digital camera lenses are also of first-class quality. Canon lens has sharp imaging and true color reproduction, which effectively ensures the final imaging quality. At the same time, it also designs and provides lenses for some digital camera manufacturers, such as Casio.
Nikon Nicol lens: Nikon is a world-famous lens manufacturer with the same reputation as Canon, and its Nikkor series lenses are loved by photographers for their excellent imaging quality. Nikon's digital cameras all use Nicol series lenses, especially some high-end models, and also use expensive ED (ultra-low dispersion) lenses to obtain perfect images. Although these high-end models are expensive, many photographers don't choose them because their lenses are excellent, not Nikon's digital cameras.
Minolta GT lens: Minolta is also a well-known optical equipment manufacturer. One of the highlights of its digital camera is the GT lens-the letter "GT" indicates that it is an advanced lens specially used for digital cameras, which means that this lens is an extraordinary high-quality lens made by concentrating Minolta's unique key image processing technology (GT=G Lens Technology), which keeps chromatic aberration and distorted astigmatism to a minimum. Most of Minolta's DiMAGE series digital cameras use GT lenses.
Olympus: The fully automatic cameras produced by Olympus have a large market share in China, and its digital camera brand CAMEDIA is also deeply rooted in people's hearts. CAMEDIA series cameras all use the lenses designed and produced by Olympus, and some use the lenses with the maximum aperture of F 1.8, which is very rare in digital cameras. Olympus also gave this kind of lens a nice name-super bright.
Fuji's Fuji Dragon Lens: In addition to producing and selling films all over the world, Fuji is also a traditional camera manufacturer, and its lens brand is Fuji Dragon. After entering the digital age, Fuji is making every effort to promote the popularization of digital cameras. In order to ensure the excellent imaging quality, Fuji has made great efforts in the lens, and used super EBC coating on the lens, which has played a great role in improving the performance of the lens, which is enough to show Fuji's good intentions.
Pentax lens: Pentax's fame doesn't seem as loud as the brand mentioned above. Actually, it is not. Pentax is not only highly accomplished in the field of 135mm professional SLR cameras, but also in the field of medium-sized professional cameras. It is also for this reason that he doesn't have many opportunities to meet ordinary consumers. Pentax doesn't have many digital cameras, but each camera uses excellent Pentax lenses. In addition, Pentax also designs and supplies lenses for other manufacturers, such as Casio.
Carl. Zeiss lens: Carl? Zeiss lens is a brand from Germany and one of the few non-Japanese manufacturers at present. Carl. Zeiss is a manufacturer of optical instruments with a long history, and its lens has always been synonymous with "nobility" in the field of traditional cameras. Many color lovers have Carl? Zeiss is proud of the camera. Sony has used Carl in some of its digital cameras. Zeiss lens, and use it as a selling point. It should be noted that Sony generally uses Carl? Zeiss lens, while ordinary Sony lens is used for low-end products.
Leica lens: Leica is also a German optical instrument manufacturer with a long history.