DC
digital camera. What people call DV is a digital video camera.
Pixels: 68p'
Simply put, a pixel can be regarded as a point. Such a point has size and area. The size unit can be converted into centimeters. The formula I Can't remember clearly. Photos are made up of many such points. Each point records the corresponding color information. The relationship between pixel size and display resolution can be understood as: at 1024*768 resolution, it is just right to use 1024*768 photos as wallpapers. 1024*768=786432. Simply think of it as so many dots, so many pixels, about 800,000. In other words, an 80-megapixel camera can take such large photos. O
Generally speaking, it can be roughly thought that a 1 million pixel photo is a photo of 1024*768 size, and a 2 million pixel photo is 1600*1200. As for the corresponding photo development, 1 million can develop 5-inch photos, barely 6 inches; 2 million can develop good 5-inch photos, 3 million can develop 7-inch photos, and 4 million can develop 8-10 inches. But this is not absolute. In addition to pixels, the quality of developed photos also depends on the degree of image compression and your acceptance of the developed photos. If you can accept larger particles, just enlarge. $1
Generally speaking, 2 million is enough for a family, 3 million is enough, and more than 4 million is really not necessary. You can think about how many 5-inch photos you have at home, how many photos are larger than 5 inches, and how much money you have to develop and enlarge photos of great people all day long. Generally, people who buy digital products do not want to develop photos. If you only watch it on a monitor, the requirements are lower. Generally, the monitor resolution is 1600*1200, 1280*1024, 1024*768, and 800*600. Four million is 22xx*17xx. With my Canon G3, I took less than 30 16xx photos at 4 million, and the rest were at 2 million. -Z`
There is another thing to note: large photo sizes take up a lot of space. Taking the 32M CF card that comes with POWERSHOT G2 as an example, Canon’s official data shows that 1,600 x 1,200 normal image quality (JPEG format) can store 104 pictures; 2,272 x 1,704 normal image quality (JPEG format) format) can save 54 pictures; if you use 2,272 x 1,704 for the best effect and use lossless compression format, you can only save about 10 pictures. That is, if you want to print or develop good photos, you have to pay the price of storage space. However, if you are just looking at it on the computer, don’t worry too much about the storage capacity of the card. Let’s use the machine just now as CCD (cmos) O~g
This is the photosensitive element of a digital camera. At present, Say, most low-end cameras (many 800,000-pixel and 1-megapixel cameras) use CMOS, and generally most use CCD. The photosensitive principles of CCD and CMOS are different. The 800,000-pixel and 1-megapixel cameras on the market use CMOS to reduce costs, which is one of the reasons why these cameras are cheap, but the imaging effect is... miserable. .
In principle, it is not recommended to buy 800,000-pixel and 1-megapixel images because they are not CCD photosensitive originals. The 640 x 480 normal image quality (JPEG format) commonly used on web pages can store three images. More than a hundred. p
ISO
The ISO value describes the sensitivity to light. The larger the ISO, the faster the photosensitive speed. In order to allow the object to get enough exposure on the photosensitive medium to form a clear image, we use a high sensitivity to shoot night scenes or fast-moving objects. However, it does not mean that the higher the ISO, the better. For digital cameras, high ISO pictures will have a grainy feel, and too high an ISO will also cause a lot of noise in the picture. When choosing a camera, you must consider the range of ISO values.
Sharpness: "w: Q4
To put it more simply, sharpness, didn't we just talk about pixels? Sharpness can be understood as the contrast between each point and its surroundings. Think about it, if the difference between each point and its surroundings is large, would it feel clearer? Therefore, a picture with high sharpness will give people a clear feeling, but if the sharpness is too high, it will be miserable because the sharpness is too high. , the edges of the graphics will appear jagged, and the graininess will be obvious |
Focal length: NS~[
The camera lens can be regarded as a magnifying glass. We know that a magnifying glass can focus light. One point, this point is the focus. The focal length is the distance from the focus to the center of the mirror (to be precise, it is the distance to the optical center). When we talk about a lens of several millimeters, the millimeter here is the value of the focal length. p>The focal length value is small, and the imaging range is large (because the light is severely deflected), which means that the scenery seen in the photo is wide; for example, when taking pictures of landscapes, we hope to take in the blue sky, white clouds, green mountains, green water, gentle breeze and setting sun as much as possible For images, a small focal length should be used. A lens with a small focal length is called a wide-angle lens. If the focal length is large, the imaging range is small, but the image we see is large. For close-up photos of models, use a larger focal length to make them clearer. Also, if you are taking photos of sports competition scenes where you are afraid of being hit by a shot put if you are too close to the venue, you should also use a lens with a long focal length. We call it a long lens. Cq
The lenses used by sports reporters and paparazzi are just like those used by rocket launchers. We call them telephoto lenses. Jq?
Optical zoom: 2Kt@
In a traditional camera, the focal length of a lens is fixed. We can change the focal length by changing the position of each lens (this will be discussed later). (Explanation) Let’s make a difference. The principle of zooming is the same as that of traditional cameras, which is called optical zoom. The focal length of DC is smaller than that of traditional cameras, but for the convenience of comparison, the focal length is equivalent to that of traditional cameras, such as the Canon G3 focal length. Equivalent to the traditional 35-140mm, divide 140 by 35 to get 4. This 4 is a 4x optical zoom, which is also equivalent to a 4x telescope:
The advantage of optical zoom is: you can stand still. You can change the picture size by zooming. As mentioned in the above post, use a wide angle when taking pictures of scenery, and use a telephoto lens when you need to zoom in or take a distant view. For example, there is a cliff in front of you. You are admiring the scenery and suddenly find a pine tree growing in the gap of the cliff in the distance (not too far away). You decide to take a close-up of this vigorous vitality. OK, zoom to 1xx-2xx mm, but done! , what should I do if it’s a 35mm fixed focus (the average household fixed focus DC is about this value)? Then try to jump in that direction. Generally speaking, the wide angle should be as small as possible, and the telephoto should be as large as possible, good! The scenery is large, and the telephoto lens is just like a telescope. However, the large optical zoom range also affects the image quality. For example, the Olympus C730 has a 10x zoom, which is great as a telescope, but the picture quality is not as good as some other DCs.
Digital zoom: i
The principle of digital zoom is different from that of optical zoom. It does not optically magnify the actual object, but magnifies the image that has been formed on the CCD, that is to say , which is equivalent to enlarging the photo. This kind of magnification is not the effect of using a magnifying glass to look at the photo, but calculating each point on the photo so that these points occupy a larger area. The image obtained by digital zoom is poor! The feeling is vague. Just imagine, what would happen if the color originally applied to a large area of ??millet is applied to an area the size of a mung bean? What you see this way is not a detail, but a color spot or block of color. GfBfp
Think about it, is MM’s photo comfortable to look at with the dots that are almost indistinguishable to the naked eye, or is the effect of the piles of color blocks/spots outstanding? Therefore, digital zoom is just a lie on DC and has no practical use at all. On a computer, this can be achieved using some graphics processing software.
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When buying a DC, don’t look at how many times the digital zoom is, it’s useless! It’s no use multiple times! When processed by a computer, digital amplification is higher than DC. The greater the digital amplification, the worse the effect. To zoom, you need optical zoom! Optical zoom basically does not affect the subtle parts of the image. After optical magnification, the image is still composed of points (rather than blocks). t
In addition, some digital cameras can combine optical zoom and digital zoom. It is recommended that the digital zoom be turned off
Storage medium 3S8~o
DC memory cards are generally semiconductors that can retain data after power is turned off. They have no mechanical parts and are small in size. Light weight and low power consumption. y#x
DC also has other storage media, such as small hard drives and CDs. Small hard drives are too expensive and consume power. If you need large storage space, it is recommended to use other methods. CD, no good, don’t use it (it’s hard to hold, not compatible, and consumes a lot of energy). $y
The commonly used cards in DC are W
CF, MS, SM, SD, MMC, and XD. The size (not capacity) of the card decreases from left to right. .
CF card (compact flash), nDlt; 4g
There are two specifications: CFI and CFII. The difference is basically in parameters and specifications, which is of little significance to ordinary users, but don’t worry , there are many basic CFIs on the market, and CFII is backward compatible with CFI, which means that if you can use CFII, you can plug in CFI. Nowadays, DCs that use CF cards basically take both types. Just buy CFI (you said buying a CF card, JS Just give you CFI and will never give you CFII unless you specify). F?a
There are DCs that use CF, CANON, NIKON full series, Minolta D5 D7 series, OLYMPUS C5050 also uses CF. i
It is best to bring a camera with you when buying CF. There are many CF manufacturers now, some are not compatible, and some have DC cards (such as D5 D7). The disadvantages of CF are that the capacity is not too large (but 256M is basically enough), the speed is not very fast (cannot be felt), and the size is relatively large (much smaller than a camera). It is used in most machines, including professional SLRs, so it has the widest compatibility. In addition, the price is cheap, and the advantages are obvious: I borrow one from a friend when I go out to play, and who makes it compatible with me? There are no disadvantages. Xiao: Friends may also go out to play. ]
The memory stick used by SONY_=jTw
It is called memory stick or MS for short. !j hi
SONY is rich and awesome. It launched MS by itself, which means that SONY DC can only use memory sticks, and SONY DC can only use memory sticks, so this thing is not compatible, and The transmission speed is not that fast either. What's even worse is that the price is a rip off. X
Although SONY's MS is not compatible with other cards, it is not useless. Memory sticks are universal for other SONY products such as camcorders, MP3s, etc. If you plan to follow SONY all the way To the black, you can avoid repeated investment, 2fTN
However, we must also remind you that SONY's MEMORY STICK PRO is now incompatible with the previous MS. That is to say, the new memory stick cannot be used with previous SONY products. , everyone must pay attention to the distinction when buying SONY DC cards. The ones that are compatible with PRO are the latest (relatively the most expensive) machines. '9
SM card: smart media card#hu4~c
Compared with the CF card, the SM card removes the control circuit and has no special interface pins. It only uses surface circuits. The contacts are connected to the reading device. Because there is no control circuit, SM is much thinner than CF, and the cost is much lower. However, it also seems a bit fragile (as thick as a few sheets of paper, but not much smaller than CF). SM cards should be cheaper than CF cards, but the price is limited. When you buy it, take the camera with you and try it out to see if there are any compatibility issues.
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The machines that support SM cards are Fujifilm and Olympus. xoP
MMC card and SD card?H\OYamp;
The appearance of these two cards is the same, but MMC cards are rare and not commonly used, and SD cards are relatively more commonly used. Panasonic, Minolta, Kodak and other small manufacturers use SD cards. (Generally, anything that can use SD can use MMC.) SD cards are more expensive, the price is about the same as a memory stick, and the volume is smaller than CF, SM, and MS. Small. ez
Let’s talk about the last one - XD card gt;
This card was recently jointly launched by Olympus and Fujifilm. It is a very small card (such as the one above The picture above) has a larger capacity (currently 128M, which is not big at all, but will it be launched in the future? G) and faster speed. fscYQ4
New machines from Olympus and Fujifilm such as Olympus C5050 (eat SM, CFI CFII, XD4 types), U300, Fujifilm S304, etc.
Noise and dead pixels Plt; 5:
As mentioned before, DC is a photosensitive element (CCD or CMOS or other, mostly CCD) that senses light and then converts the light signal into electrical signals, processed, and then imaged. The CCD is composed of millions of photosensitive units. During the photosensitive process, if a certain unit on the CCD is damaged, this place will not be able to sense light, and there will be a white dot on the final image. This dot is a dead pixel (dead pixel). ). As for the noise, it is because the photosensitive unit will generate heat during the photosensitive process, and the temperature will rise, so the noise will increase. When the noise increases to a certain level (when the camera's noise reduction system cannot eliminate it), noise and dead pixels will be detected in the picture: ~ xe
Put the camera lens cover on. If there is no lens cover, such as the one for NIKON2500, find something opaque to block it. Remember, no light should be exposed during the test! Then press the shutter. The shutter time is generally set to 1/60, 1/8, 1/4, 1/3, 1/2, 1, 2, 3, ... the maximum, then adjust the sensitivity, and then Try it. If it is a point-and-shoot camera and these cannot be adjusted, then there is no other way. Try to slow down the shutter. Since noise only appears when the shutter is open for a long time and the sensitivity is high, it is best to try each at the slow shutter stage (which is more troublesome). 'l1O2^
After taking such a photo, theoretically the image should be black (but in reality it is impossible). The location of dead pixels is fixed and will appear regardless of the shutter speed or sensitivity. Noise is not necessarily the case. The location is not fixed. Whether the shutter is fast or slow, because the exposure time is long, the CCD will heat up, which is inevitable. Because of this, DC has more noise when used for a long time than when it is first turned on. `j
Check to see if there are any bad pixels and noise. You can’t see them clearly on the DC LCD screen, that’s for sure! To view the original picture on the computer, you need to transfer the photos to the computer, use PHOTOSHOP or ACDSEEE or other picture viewing software to view the 1:1 picture, look up, down, left, and right, and compare several pictures (there are no bad pixels). 6
If it’s still not enough after reading it, it’s best to use software, deadpixeltest software. j=
Variable spots remain on the film. This spot is noise. I
Dead pixels are acceptable defects under the current technical conditions. In other words, it is legal to have one to three dead pixels. One or two points won't affect the image quality very much, but it will make people uncomfortable! Therefore, when buying a DC, you should check for bad pixels on the spot. If there are any, let JS replace it. Anyway, we are still God until you pay the money. If you pay the money, just appoint it. The Consumers Association cannot save you. D~9]#
Noise (hotpixel) is inevitable, and the same type of machine may have more or less noise. Therefore, it is best to compare several machines and find the one with the least noise. hW
A good DC has a noise reduction function, which is turned on when the shutter is slow, which is very important for night scene photography. Moreover, the shutter speed should be lowered when the light is poor. However, noise reduction comes at the expense of details, but without noise reduction, it may be the photos that are sacrificed.
Therefore, I personally think that noise reduction is still more important. However, some DCs without noise reduction can still produce acceptable night scenes. r_8O
There is another point that I forgot to mention, and that is the bad pixels on the LCD. This is an acceptable flaw. What, if you say you can't accept it, then you have to be careful and choose one that doesn't have them. Dead pixels on the LCD screen do not affect the image, so even if there are any, the harm is not too big. Of course, it's still no good. Take a light-colored picture (must be clear) and a dark-colored picture. Use DC playback mode and zoom in to see if the color of the dot does not match the actual color and the position of the dot does not move with the movement of the image. If so, this is white balance: '
White balance is a function that helps the camera identify white colors. It’s not that the camera is too stupid to recognize white, it’s just that it’s too strict. When we enter a room with light bulbs on (more obvious when there are spotlights), in theory, things that are originally white under daylight, such as walls, will have a little yellow under the light of the lights, because the color of the light changes. , shooting on objects will have different effects (see general physics for details). However, after the information received by our eyes is processed by the brain, it will be regarded as white, but CCD will not work. CCD maintains meticulous The scientific attitude reflects truthfully, and the consequence of this is that we cannot bear it. In the photos produced like this, PLMM will either turn into a yellow-faced woman (twilight, incandescent lamp, etc.), or a green-faced fang (fluorescent lamp, etc.). In order to allow us to accept the effect and ensure the safety of poor photographers like us, DC has a function such as white balance. Automatic white balance uses a set of automatic procedures to enable the camera to identify which part is white, and then determines the image based on this. 'gt;^7
Some DCs have excellent automatic white balance and can accurately reflect colors under any lighting conditions. However, when the automatic white balance is not so good, you need to change it. There are white balances at dusk, incandescent lamps, fluorescent lamps, etc. This is because the camera takes these common occasions into consideration and balances colors under these lighting conditions. In these cases, you need to select the corresponding white balance (if automatic is accurate, you can ignore it). If the ambient light shows these situations, which are more complicated, such as in museums, hotel lobbies, etc., you need to use manual white balance and let us personally help it find the feeling. |x: PP
Manual white balance: t
This function must be available on the camera. Turn on this function (usually search it in the menu), then find a white object, wall, paper, etc., the area should be enough to fill the camera's viewfinder, and then press some button (some half-press the shutter, some have special buttons) ), even if it is defined. O
^
Talk about batteries: G
DC is a large consumer of electricity, so good batteries are essential! S
When using DC, a rechargeable battery is required because DC requires a large discharge current. Generally, electrical appliances that require large currents, such as DC and four-wheel drive vehicles, are charged. To advise you like this is not to underestimate your financial strength, because I am afraid that you will not be able to afford the battery. The alkaline batteries on the market cannot withstand high currents, and generally ten minutes are enough. ^k
There are several types of rechargeable batteries. I don’t know how many there are, only the commonly used ones. 1"M
Nickel-cadmium battery: This is actually not commonly used, but a few days ago a friend bought a Walkman with this kind of battery, which is infuriating! The disadvantage of nickel-cadmium batteries is that they have serious memory effects! Also That is to say, the electricity must be completely discharged before charging. If there is still residual electricity, the battery will use the capacity discharged in the last discharge as the capacity for subsequent charging. To put it simply, you can charge it with 80% of electricity left. The battery is equivalent to the original 20, which is basically useless. ]4K~m
Lithium battery: The advantage of lithium battery is that it has no memory effect! The charging time is relatively short, like Canon's BP511, it can be charged in 80 minutes. 90, but the remaining 10 is slower, about an hour. Lithium batteries are generally specially designed and can be very small, which is very helpful for reducing the size of the camera, but the problems it brings are: The versatility is poor. DC lithium batteries cannot be used universally, and it is very expensive to buy a spare. They are not sold everywhere like AA batteries.
gn; The advantage of nickel metal hydride is that it can be made into the shape of an ordinary AA battery. Using the DC of this kind of battery, you can use ordinary AA batteries for emergency use after the power is exhausted. The disadvantage is that the charging time is slow, usually taking one night. Of course, there is fast charging now, which can be done in more than an hour, but fast charging involves a violent chemical reaction in the battery, which affects the lifespan. ; Ro
Because the battery has a lifespan when charging and discharging, and has a number of cycles. Someone (pchome, the post is hard to find) has done calculations. The result is: a fully discharged battery can be charged more during its life. . When the battery life is over, the charging and discharging endurance is no longer good. g/vU1
New batteries or batteries that have not been used for a long time should be activated, such as warming up before exercising. The solution is to cycle it full and empty several times. Because the battery is not used for a long time, the activity of the chemical substances will become worse, so that the capacity will not reach the normal value. After activation, it can reach normal. Od9
The nickel metal hydride charge should be charged for a while, maybe 14-15 hours. You need to charge it for a while every time you activate it again. GB\
The lithium battery also needs to be activated, but it only needs to be fully charged and drained several times. It is not necessary to charge for more than 10 hours for the first time like the legend. Lithium batteries have very strict requirements for charging and discharging, because lithium batteries have powerful and strict protection circuits. This protection circuit is troublesome and makes it difficult to make lithium batteries into AA shapes. When fully charged, a protection circuit prevents further charging, and the battery naturally discharges in the air. If it is still on the charger at this time, it is equivalent to performing a charge and discharge cycle, which is meaningless. Lithium batteries cannot be overcharged or overdischarged. The protection circuit also works during discharge to prevent battery damage due to overdischarge. y!mH
Because it cannot be over-discharged, the battery will naturally run out of power in the air. Therefore, when storing lithium batteries, some power (70 to 80%) should be reserved to avoid being unable to charge in the future.