Introduction of SLR camera.

Ultra-wide angle: generally, it belongs to ultra-wide angle below 28 mm.

Wide-angle: Generally, all below the header are wide-angle.

Title: 55MM official traditional lens belongs to the title.

Medium coke: generally 70- 135MM belongs to medium coke.

Telephoto: telephoto above 2 10MM generally belongs to telephoto.

Ultra telephoto: Anything over 500MM 1000MM belongs to ultra telephoto.

When shooting birds, because the birds are far away, they usually choose telephoto; When shooting scenery, you need a big scene, so it is a wide-angle lens. 85mm standard lens is very good for taking portraits, so it is called portrait head. 100mm fixed focus lens is called Budweiser, and the macro is very good.

Two. drawing

APS is positioned in the amateur consumer market. In order to increase the public's interest in photography, APS designers changed the single frame format of 135 system and designed three (C, H, P) negative frames:

The H-shape is the whole frame (30.3× 16.6mm), and the length-width ratio is16: 9;

Type C is at one end of the left and right ends of the whole frame, and the length-width ratio is 3:2, which is the same as that of 135 film;

P mode is called panoramic mode, which blocks the upper and lower sides of the whole picture one by one, so that the aspect ratio of the picture is 3: 1.

The CCD size of SLR digital cameras is xx. Xx× xx mm (for example, 23.5× 15.7mm). The CCD size of ordinary DC is x/x.x inches (for example,11.7 inches), and11.7 inches is diagonal.

120 film and 135 film: 135 generally refers to 35mm film with a size of 36mm by 24mm. The membrane of 120 is larger, with dimensions of 6*4.5, 6*6, 6*7, 6*9, 6* 12 cm. 135 negative camera is also small and portable, used for family, news, documentary photography, etc. 120 negative film is fine in quality, suitable for taking photos with high quality requirements such as landscapes and portraits. At present, most cameras on the market are 135 cameras.

Three. Lens parameters

Relative aperture: It represents the ability of the lens to pass light, expressed by D/F. For example, if the maximum aperture diameter of a lens is 25mm and the focal length is 50mm, then the maximum relative aperture of this camera lens is 1/2.

Aperture: The reciprocal of the relative aperture is called the aperture coefficient or aperture number of the lens, also called F number, that is, f = f = F=f/D d, and the aperture number should be marked on the lens. For example: 1.4, 2, 2.8, 4, 5.6, 8, 1 1, 16, 22 ... If the influence of various lens transmittance differences is not considered, no matter how long the focal length of the lens is, how big the aperture diameter of the lens is, as long as F number is a particularly important parameter for lens. The smaller the F number, the wider the scope of application of the lens, so the smaller the F number, the higher the price. The smaller the number after f is, it is called a large aperture, and the blades controlled by the lens are almost fully open, indicating that more light enters. The larger the number after f, the less light there is, which means that the lens control blade is not obviously opened. In addition, the smaller the value after f, the easier it is to highlight the subject and blur the background. The greater the value after f, the smaller the difference between the subject and the background, and the larger the clear range.

Angle of view 2 Ω: In fact, as far as 135 camera is concerned, its standard frame has been determined to be 24mm X 36mm, and its diagonal length is 2η=43.266. There is the following relationship between the focal length f of the lens and the viewing angle ω:

tgω=η/f

Where: 2η- diagonal length of frame; F- the focal length of the lens.

Four. Fundamentals of photography

Color temperature: at a certain temperature, the color of the light emitted by the light source is the same as that radiated by the blackbody, and the temperature of the blackbody is called the color temperature of the light source. The bluer the light color, the higher the color temperature; The lower the color temperature of red. Different color temperatures of light sources lead to different light colors. The color temperature below 3300K is stable and gives people a warm feeling. The color temperature of 3000-5000 K is the middle color temperature, which has a refreshing feeling; The color temperature is above 5000K, and it feels cold. Under the irradiation of high color temperature light source, if the brightness is not high, it will give people a turbid atmosphere; Under the irradiation of low color temperature light source, too high brightness will give people a sultry feeling.

Color temperature of light source

Northern clear sky 8000-8500k

6500-7500k on cloudy days

Summer noon sunshine 5500k

Metal halide lamp 4000-4600k

Afternoon sunshine 4000k

Cold fluorescent lamp 4000-5000k

High pressure mercury lamp 3450-3750k

Warm color fluorescent lamp 2500-3000k

Halogen lamp 3000k

Tungsten lamp 2700k

High pressure sodium lamp 1950

Candle lamp 2000k

White balance: the colors of light emitted by different light sources are different, and the colors of objects will change due to the different colors of projected light. Photos taken by the same object under different lighting conditions will have different colors. The human eye can distinguish various colors, but the CCD of DC does not have this function; In order to make the color of the image shot by DC basically consistent with the color seen by human eyes, it is necessary to adjust the "white balance". White balance can make the color of photos taken by DC in various light conditions basically the same as that seen by human eyes.

Balance means that the digital camera defaults to "white" regardless of the ambient light, that is to say, it can recognize white under colored light and balance the tones of other colors.

Manual white balance function, that is, set white balance parameters according to standard white. Under the lighting condition of the shooting scene, aim the DC lens at the pure white object to make the scene full of DC viewing range, and manually adjust the white balance.

In addition, white balance can be used flexibly when shooting. When shooting with a flash, the color temperature of light emitted by an electronic flash is basically the same as that of sunlight, so the white balance should be set to sunlight, even when shooting at night. This setting is also good for restoring the color of close-range characters, while the foreground light is generally warm yellow in photos, which most people like. If you only have a distant view and no close-up people when shooting at night, you can set the white balance to incandescent lamp. Don't use automatic white balance when shooting flowers, just adjust it according to the light source at that time. If you shoot flowers in the sun and adjust the white balance to incandescent lamps, you can make white flowers shoot some blue, just like the "blue witch" sold by Valentine's Day flower shops! When shooting sunrise or sunset, the color temperature is relatively low. Don't use automatic white balance or set it to incandescent lamp, set it to daylight. The photos taken in this way will be redder and more in line with the atmosphere at sunrise or sunset.

Depth of field: What is depth of field? Simply put, it is a clear part and a fuzzy part in a photo, which makes the subject clear and the background blurred. Sometimes we need greater depth of field, for example, when taking a group photo, we hope that the people in the front row and the people in the back row can express clearly, and sometimes we need to control the depth of field slightly smaller, for example, when taking a single portrait, in order to highlight the characters, we blur the background behind the characters, so we must control the depth of field on the characters, and sometimes control the depth of field within a certain distance in order to achieve a certain effect.

So, how can we control the depth of field? Control the depth of field from two aspects, one is the aperture and the other is the focal length! Forget the complicated theory. The depth of field is the smallest and the blur effect is the most obvious when the inverse aperture is large and the focal length is long. This is the truth from theory and experience. Just remember it when you take pictures, but how to use it is a personal matter.

Aperture priority: the user decides the aperture size, and then the camera calculates the amount of light according to the ambient light and exposure settings. This mode is more suitable for shooting still objects.

Shutter priority: the user decides the shutter speed, and then the digital camera calculates the appropriate aperture size according to the environment. Therefore, shutter priority mode is more suitable for shooting moving objects, especially digital cameras are very sensitive to vibration. Even shaking the camera slightly will produce blurred photos during exposure, which is more obvious when using a long focal length.

Constant aperture: Constant aperture and floating aperture are corresponding concepts, which are generally used for zoom lenses. Constant aperture usually means that the zoom lens can use its nominal maximum aperture in all focal lengths. For example, the lens indicates 28-70 mm/2.8, which is a constant aperture lens. This means that the lens can shoot at a focal length of 28-70mm, and the maximum aperture value is F2.8 If the lens logo is 28-70 mm/3.5-4.5, it is a floating aperture lens, that is, the maximum aperture of 28mm focal length can be F3.5, and the maximum aperture of 70 mm can only be F4.5. ..

Generally speaking, a constant large aperture lens has the following practical significance:

1。 You can get a faster shutter speed in dark light, which is suitable for photography in dark light.

2。 A smaller depth of field can be obtained. This can get a more blurred background when shooting portraits.

3。 Generally, better shooting quality can be obtained. Generally speaking, lenses with constant large aperture belong to professional lens series, and the lens quality is better than that of floating aperture lenses.

The complete series of aperture values are as follows: f 1, f 1.4, f2, f2.8, f4, f5.6, f8, f1,f 16, f22, f32, f44. The amount of light entering the upper layer is exactly twice that of the lower layer. For example, if the aperture is adjusted from f8 to f5.6, the amount of light entering will double. For consumer digital cameras, the aperture f value is often between f2.8-f 16.

In fact, it is of little significance to use a constant large aperture in wide-angle zoom, because it is rarely used in landscape photography and is only used in photography where the depth of field is often controlled.

ISO:ISO sensitivity is an index to measure the photosensitive speed of film used in traditional cameras, which reflects the photosensitive speed of film (actually, the photochemical reaction speed of silver and light). The ISO sensitivity of a digital camera also reflects its exposure speed. When the ISO value increases by 1 times, the photosensitive speed also increases by 1 times.

The ISO sensitivity means that if you choose a higher ISO sensitivity under the same EV exposure value, you can get the same exposure with a faster shutter speed under the same aperture. On the contrary, a smaller aperture can be used to maintain correct exposure without changing the shutter. Therefore, when shooting in dim light, you can often choose a higher ISO sensitivity.

Night shooting often uses a smaller aperture and a longer exposure time. If you choose a higher ISO sensitivity, it will inevitably produce noise and noise. At this time, a tripod can be used, and cable release may be used again. By choosing a lower ISO sensitivity, noise and noise can be avoided.

The performance of various digital cameras is different under different ISO sensitivities, so it is necessary to test them, even if they are improved, they should be controlled within a tolerable range. Because, although it can be adjusted by software later, it will inevitably reduce the clarity of the image accordingly.

Therefore, when buying a digital camera, you need to consider choosing a camera with noise reduction function. The lens aperture is larger, which is more conducive to shooting in low light. Try to use flash and tripod when shooting, and try not to use one with higher ISO sensitivity.

Generally speaking, outdoor 100-200, indoor 400, and evening 100-200. The same is true for lighting. Without lights and shelves, there will be a high sense and poor effect, and it will only be used when there is no way. If the shutter aperture combination is not adjusted in place, ISO can also be used to achieve the goal. Generally, the sensitivity of 400-800 is helpful to show the details, but it doesn't make much sense to be higher. If the film is to be clean, it is almost a general principle to choose the lowest sensitivity possible.

Original format:

Some people say that the storage space of RAW is too large, and the conversion of special software is too troublesome. If you don't pay much attention to photos, there is no need to use RAW format. RAW format has its unique advantages, and this format is also the original data recording method that experts like.

RAW files are almost unprocessed information obtained directly from CCD or CMOS. Through post-processing, photographers can maximize their artistic talents.

RAW file has no white balance setting, but the real data has not been changed, which means that the author can adjust the color temperature and white balance at will without loss of image quality.

On a computer with a microprocessor, color linearization and filter row-column transformation can be processed faster, which allows the application of some more complex algorithms that are not allowed on a camera.

Although the RAW file is attached with marking information such as saturation and contrast, its real image data has not changed. Users can freely make personalized adjustments to a picture without having to base on one or two preset modes.

Perhaps the biggest advantage of RAW is that it can be converted into 16-bit images. That is to say, there are 65536 levels that can be adjusted, which is a great advantage for JPG files. This is very important when editing images, especially when you need to make important adjustments to shadow areas or highlight areas.

Exposure compensation: additional auxiliary adjustment mode of automatic exposure control mode. In addition to the automatic program control mode, automatic exposure control needs to set one factor of aperture or shutter in advance, and the other factor is set automatically by the camera. If further adjustment is needed under a given exposure combination, it must be achieved through exposure compensation. When adjusting exposure with exposure compensation, the actual adjustable factor is the camera control factor, not the predetermined factor. For example, when an aperture is used, exposure compensation adjusts the shutter speed; When using the shutter speed, the exposure compensation is adjusted by the aperture value. When adjusting the exposure manually, most cameras can only adjust one EV. When the exposure is automatically controlled, the exposure compensation can be adjusted not only by 1EV or 2EV, but also by 1/2EV and 1/3EV, which is more flexible to use. camera

Learn to add white and subtract black. If you shoot black, you should reduce your exposure. If you encounter white, you should increase your exposure and measure your feelings. The reason is that the camera always uses the gray scale of 18% to judge the subject. If the photometric position in the scene is 18% gray, then the scene will be truly reproduced, but when measuring white objects, then the camera thinks that our subject is 18% gray and then exposes it, then the white will turn gray, so the exposure should be increased. This is also a principle. Therefore, exposure compensation can actually be omitted. Why do you say that? I found a subject photometry in the scene similar to 18% gray scale, so the exposure is accurate, but in fact, many scenes do not have accurate 18% gray scale, so this one has exposure compensation function. Our exposure combination is generally related to the measured light. According to Bresson's method, the scene is divided into ten areas, and his light is measured in five areas, so that the shot scene is basically close to the original scene. This requires long-term training.

Histogram/histogram: A digital image consists of many squares (pixels) with the same color. Because these squares are small, they look exactly the same. Because it is difficult to distinguish pixels only by color, engineers distinguish pixels according to 256 levels of brightness, from black (0) to white (255), with 254 gray levels in the middle. Image processing software automatically classifies images according to 255 levels of brightness and piles up "brightness squares". Each "heap" or "column" tells us how many pixels belong to a certain brightness.

Correctly exposed image

Underexposed image

An overexposed image

An image with high contrast.

Most quasi-professional digital cameras and all professional digital SLR provide users with real-time histogram display function. When shooting, users can watch the histogram of photos taken under a certain exposure setting through LCD, and adjust the exposure setting according to this histogram.

Hood: function: anti-glare, anti-ash, anti-splash. Generally, they are original factories, but they are not as accurate as the original factories, and it is easy to produce black edges. Under normal circumstances, the lens is taken out. When not in use, the cover can be stored on the lens.

UV mirror: the main function is to filter ultraviolet rays and protect lenses. Usually buy lenses, many friends have to go to UV. Personally, I think it is unnecessary. First, it affects imaging, and second, it wastes money. In the case of a point light source, UV will reflect light and form a speckled ghost in the photo. If you add other filters before UV, the black edge will be more serious. Of course, you can go there if you want. Generally, UV has single film and multi-film, with different thickness, different brands and different prices. Don't go there for tens to hundreds of dollars and cheat money from merchants. When tilted under a fluorescent lamp, the multilayer film UV will have images of multiple tubes.

Circular polarizer (CPL): used to eliminate reflection, such as shooting content through glass. The reflection of green leaves, water, etc. , but it can't eliminate the reflection of metal. Generally, the thumb is 90 degrees from the index finger, the thumb is facing the light source, and the direction pointed by the index finger is the best elimination direction. Turn the CPL and observe the extinction from the observation frame until it is satisfactory. In addition to extinction, it has a certain grey mirror effect, and can also eliminate the diffuse reflection light in nature. Therefore, when shooting landscapes, CPL is usually used to get good images.

Cleaning set: leather hair dryer, lens pen, suede.

Cameras are prone to static electricity, just like vacuum cleaners. Pay attention to daily maintenance and clean it every time you come back. After a long time, you will develop good habits. Common lens dust, fuselage dust, focusing screen dust. Blow off the dust at the interface before changing the lens, try to change it without wind or shelter, and don't change it if you can. It is best not to deal with the dust on the fuselage and lens, and spend a little money directly to the quick repair center. Suede is used to wipe the lens, and it is an animal's skin. Very soft, mainly used to wipe the lens, much better than inferior lens cloth and lens paper.

Right-angle viewfinder: mainly to change the observation direction of eyepiece, which is very useful when shooting at low angles. The original is more expensive. You can consider domestic seagulls, a few hundred dollars, without lying on the ground.

Safety shutter: the safety shutter speed is the reciprocal of the focal length, that is, the safety shutter speed = 1/ focal length. Safe shutter speed is usually a clear and fuzzy watershed. One thing to note here is whether the camera you are using is Quan Huafu or non-Quan Huafu. Pay attention when switching the safety shutter. For non-Quan Huafu cameras, the reciprocal of the lens conversion coefficient and the actual focal length after conversion should be added. The whole picture has the same focal length as the lens. For example, a 50mm lens needs to add a coefficient of about 1.6 to 550D, which translates to 50* 1.6=80, so the safety shutter should be placed at 1/80 seconds. If 50mm is used on the Quan Huafu model 5DII, it will be more than 1/50. This is a factor that needs to be considered frequently when there is no shelf, but this shutter speed has a great relationship with the actual operation level of the operator, and the safe shutter is only a reference index. If the personal stability is good, you can ensure that the shutter speed is lower. If someone shakes his hand, it may be empty again.

Metering mode: There are usually four metering modes that come with the camera:

Spot metering: It's easy to understand. Where is the focus, the camera will calculate the position. Mostly used for backlight shooting or emphasizing that the subject ignores the background.

Local measurement: mainly concentrated in the center of the picture. Generally, headshots are used more.

Center measurement: the center is the main part, supplemented by the edge. Different from the above, it is necessary to detect other parts of the picture except the middle part, and then bind the peripheral data with the central data. This metering mode is more used for product shooting.

Multi-point measurement: all operations should balance the highlights and dark parts of the picture, usually shooting large scenes, such as landscapes, snapshots and other occasions with complex surrounding environment.

Professional photographers will use exposure meters. Its principle is based on the brightness with reflectivity of 18%, which is what we often call neutral gray, medium gray or medium gray. From this, we know one thing. If you have money, you can buy an exposure meter. If you have no money, you can get a card with reflectivity of 18%. This is the grey card that is often mentioned in various tutorials. The practical use of the gray card: it should be consistent with the position of the subject and under the same light. If a person is standing in the shade of a tree waiting for you to take a picture, you take out a gray card and put it in the sun to test it. Don't pretend, people in the industry will laugh at first sight, or let people who want to take pictures hold gray cards.