Photographic background axis switch

Instantaneous exposure leaves all kinds of things, and there are thousands of words between square inches. It is the good wish of many alumni to keep beautiful moments and unforgettable memories with their own cameras.

Because of this, some friends have tasted the ups and downs of failure and success. But for more friends, photography seems mysterious, but it is out of reach.

A successful photographic work needs the perfect combination of photography technology and art, and a photographer should be a "saint".

On this page, I will introduce some knowledge about photography to my friends. If friends encounter problems in photography, they can write to us and we will answer them in a targeted way.

How is the image in the photo formed?

Anyone who has taken photos knows that the birth of a perfect photo needs to go through a complicated technological process.

The process of image formation is shown in the following figure:

1. Shooting exposure

First of all, the photographer must record the picturesque scenery and colorful scenery on the built-in film of the camera through the lens of the camera. This step is usually called photographic exposure and is an indispensable part of the whole photographic process. At this time, there is an invisible image on the film, which is called "latent image", as the name implies.

2. Development of negatives

The shot film must be developed to turn the potential image into a visible image. The work of developing film can be done by a professional development shop or by yourself. If a color negative film is used, after developing, bleaching and fixing, we can see that there is an image on the film that is opposite to the original scene and has complementary colors. Usually, we call this image a "negative image". Movies with negative images are called negatives.

I would like to remind my friends that:

Film is a special recording material, which is different from all kinds of paper used by painters and writers. This material can't be opened in a bright room before it is washed with water, and no image can be seen when it is opened. Moreover, if you open the cassette at this time, it will ruin your previous shooting results!

Don't underestimate the small negative, only its quality is good, the image in the photo can be good. The developed film must be kept clean to prevent dust and scratches. Therefore, after the wet film is dried, it should be cooled in a clean environment. Don't let dust stick to the film, and don't touch the film casually with hands or rags, which will easily leave fingerprints or scratches on the film. Don't expose the washed film to the sun, but store it in a special film bag to avoid dust. Because once there are scratches on the negative, it will leave dark stripes on the photo, and if there is dirt on the negative, it will leave a corresponding white image on the photo.

Step 3 print or enlarge

Seeing negative images is not the ultimate goal of photography. If you want to see the image with the same brightness and color as the original scene, you need to enlarge the negative image on the small negative to the required size through the lens of the printer and print it on colored paper after exposure. When you zoom in, you can cut pictures, correct colors, copy multiple pictures and copy them into different sizes. After printing, what remains on the photographic paper is also an invisible "latent image".

4. Washing photographic paper

The processing methods of photographic paper and negative film are basically similar, but not exactly the same. After development, a color image with the same brightness and similar color as the original scene will appear on the photographic paper.

The photography process involves many specific technical problems. For example, the grasp of shooting conditions and the control of developing conditions. Every link can not be ignored, because they will affect the quality of the picture.

Use and maintenance of camera

The camera is a kind of high-precision equipment, durable and reliable. This camera will serve you well if you operate it correctly and maintain it properly. However, if you don't treat it well, it will often put you in an awkward position. Therefore, when using the camera, you should take care of the camera like your own eyes.

The following precautions I hope friends will pay attention to:

1. Don't try to open the lens cover of the automatic camera by hand. The lens cover will open automatically only when the switch is turned on, and will close automatically when the switch is turned off.

2. If the camera has a date display mode, don't take it out until the battery is dead, because the date function needs battery power to keep it continuous.

3. Automatic cameras should use films with DX codes. When buying film, please make sure that the tape is marked with DX code. If a film without DX code is loaded, the sensitivity will be automatically set to a certain value, regardless of the true sensitivity of the film, which may lead to incorrect exposure.

Be very careful when using and carrying the camera. Don't drop or smash the camera to avoid strong vibration, impact or squeezing. When carrying a camera on a motorcycle, car, boat, plane, etc. You should protect it with a thick cushion. When using a tripod, be sure to stand firm, especially to prevent the tripod from being kicked over or blown down by the strong wind.

5. Avoid putting the camera in the closet with sanitary balls, or in the laboratory with chemicals that will seriously damage the camera. It should be stored in a cool, dry and well ventilated place. Never use paint thinner, alcohol or benzene to clean the camera.

6. If you take the camera from a low-temperature outdoor to a warm indoor, water vapor will condense into water droplets inside and outside the camera. When you bring the camera into a warm room, you should put the camera in a box or plastic bag to make the temperature of the camera change gradually. When the temperature difference decreases, open the bag again.

7. The normal working temperature range of a general camera is 40℃- 10℃. Attention should be paid to avoid placing the drivers in high temperature and humidity environment for a long time, such as cars in summer.

8. Dirt, dirt, dust, moisture, harmful gas or salt water that seeps into the camera will damage the camera and make it unable to run. At the seaside, it is necessary to prevent the camera from touching the salty and humid air, and to prevent the camera from splashing any liquid and rain. When the camera is caught in rain or damp, it should be dried.

9. When replacing batteries, all old batteries should be replaced at the same time. Batteries of different brands, models and trademarks, or old and new batteries cannot be mixed. Don't damage or charge the battery, and don't bake the battery on fire, because it will cause battery leakage, self-heating and explosion. The battery should be installed according to the positive and negative poles shown.

10. Never try to disassemble the camera.

Because the lens quality has a great influence on the imaging quality, it is also one of the finest parts. So its use and protection is more important.

First, keep the lens clean.

When you hang the camera around your neck, the lens must be covered with a lens cover or a transparent UV mirror to protect the lens from dust, oil or other debris, and don't accidentally leave fingerprints on the lens. Don't stack the lens with other objects without covering it, don't touch the lens with your hands at will, or let hard objects touch the lens, and don't get into the habit of misplacing it. Because the lens is dirty, it will reduce the image quality. For example, images taken with dusty lenses will have low contrast and blur. If there are fingerprints on the lens, they will be truthfully reflected in the printed photos. In your camera bag, you should have a lens brush, a hair dryer (also called an ear wash ball), lens paper and so on. If the lens is found to be dirty, you can use a special lens brush to remove dry substances such as dust, while oil stains and fingerprints need to be wiped with a special cleaner and a special soft cloth. Never scratch the lens with a hard object, because it will not clean the lens, but will do more harm to the lens-scratch the road. The light ones should be sent for repair, and the heavy ones should be scrapped.

In addition, it should be noted that lenses are generally made of glass, and the axes of lenses in each lens group and the positions between lenses are carefully designed and arranged. In the process of use, attention should be paid to prevent the lens from being strongly shaken and bumped, so as to avoid the lens glass from being broken or displaced, which will affect the imaging quality. This kind of problem is easy to happen when you put the camera on a tripod, so be more careful.

Types and selection of cameras

In the photographic equipment market, there are many styles of cameras and accessories to choose from. For most families, cameras are valuable items. Perhaps the initial snapping up of cameras is exciting, but it is also daunting, especially after the choice proved to be a very wasteful wrong choice. Therefore, it is suggested that friends decide the model according to the actual needs and economic situation when buying cameras, and don't blindly buy high-end cameras with many "extra functions".

Although some manufacturers have tried to produce a single camera that can meet all the needs of photography, the result is regrettable. No camera can meet all the needs of photography as an ideal boutique. So, either you have to limit your photography work according to the work that the camera you choose can undertake, or you have to buy several different types of cameras to meet all the needs you may encounter.

There are many kinds of cameras. According to the frame size, cameras can be divided into large cameras (such as the studio machine, which can be used to shoot loose pages), medium cameras (such as 120 camera, which is used to shoot 6 cm ′ 6 cm, 6 cm ′ 9 cm and other frames) and small cameras (such as 135 camera, which is used to shoot 24 mm ′ 36 mm frames). According to the way of framing, it can be divided into two categories: coaxial framing (single lens framing) and paraxial framing (viewfinder is located above the lens or obliquely above it). According to the degree of exposure automation, it can be divided into manual, semi-automatic and full-automatic (called "fool") cameras.

At present, 135 camera is the mainstream model of household cameras. From the experience, the camera model 135 is small in size, easy to carry, convenient for framing and focusing, and convenient for developing color film, and there are many brands of cameras, including medium, high and low grade. You can buy according to your own needs.

If it's just for taking commemorative photos or traveling with you, you can buy a 135 side camera. This kind of camera has three types: automatic, semi-automatic and manual. Generally, it has a flash and can be used in dark environment. This kind of camera is relatively simple to operate. If you want to use it for artistic creation, you still need to buy a mid-range single-lens reflex camera, but it can't be a "fool" type. There should be a manual adjustment device to manually control exposure and depth of field according to creative needs. If conditions permit, you can also match your own lenses with different focal lengths.

When making a specific choice among many brands, I suggest you consider the following factors:

1. What is the function of this camera? Are these functions exactly what you need? The main technical problems are: framing mode, working mode of focusing mechanism, focal length metering and exposure mode of lens, film winding mode and flash mode, etc.

2. Is it convenient to use?

3. Is there a corresponding series of accessories? If there are lenses with different focal lengths that don't match the fuselage, connect appropriate filters to add them when necessary.

4. Whether the price is reasonable.

After deciding to buy a certain model, you should choose carefully:

1. Appearance inspection: whether it is metal shell, plastic shell or leather, it should be flat and free of scratches, deformation and wear marks. The connection between the lens and the fuselage should be firm and tight. The back cover and the fuselage should also be seamless. There is no sign of repeated disassembly.

2. lens inspection. The quality of the lens directly affects the imaging quality, so you should pay special attention when choosing. If the lens is detachable, it can be disassembled. If it is a fixed lens, you can set the shutter speed at door B, open the back cover, aim the lens at the bright place, and check whether there are mildew, big bubbles, cracks and scratches. On a lens that transmits light. Also use the reflected light to check the coating from the side for scars. The aperture blades of the camera should be flexible and free from rust or oil pollution. When adjusting the aperture, you should feel smooth, not too astringent.

3. Check the focusing device: when focusing, the focusing ring should make people feel a little resistance, but it is not astringent and even. The image in the viewfinder should be clear and bright. If it is an automatic exposure camera, make different scenes in the center of the viewfinder and try whether the autofocus system is sensitive. In the manual focusing system, the scale line at infinity on the focusing ring should be aligned with the baseline. When observed in the paraxial viewfinder, the images at infinity should completely overlap in the center of the viewfinder, and the divided images in the viewfinder of a single-lens reflex camera should be aligned. When focusing on a close object, you can measure the distance between the scene and the camera with a tape measure to check whether the scale on the focusing ring is accurate.

4. Check the exposure device: open the back cover and shoot and expose scenes with different brightness. If it is an automatic camera or an automatic exposure camera, try the response of automatic aperture and automatic shutter. For manually exposed cameras, check whether the display data of the exposure meter changes when the scene brightness is different, and listen to whether the shutter opening time is different when exposed at different shutter speeds.

5. For cameras with flash, check the flash. Turn the flash switch to "ON" on the premise that the battery is in good condition. When the charging indicator is on, press the shutter. Try flashing the flash several times in a row, and pay attention to the charging interval of the flash, not too long.

6. Check the film conveying structure and other mechanical devices: the camera with automatic film winding should be able to automatically wind up the film after loading and shooting exposure. Manual film feeding camera should feel a certain tension when feeding film. The counter should work normally and return to zero automatically when the cover is opened.

7. Display screen inspection: For fully automatic cameras, install batteries to see if there is a display on the screen, and follow the instructions to check whether the displayed symbols are consistent with the operation results.

Finally, I would like to remind my friends that the above selection methods should be approved by the sales staff, and you should not act rashly to avoid getting into trouble.

Get into the good habit of holding a camera.

First of all, when shooting scenery, whether the picture to be shot is horizontal or vertical, the bottom of the frame must be parallel to the horizon, otherwise, the house, trees and people will look down.

Normal buildings (pictures), rickety pavilions (pictures)

In addition, when shooting with a camera, hold the camera with both hands. Take a horizontal camera as an example. Generally, you hold the camera in your left hand, focus on your left thumb and forefinger, and press the shutter with your right forefinger. Try to keep the camera still. Hold your breath and move gently when you press the shutter. If the force is too strong, the camera may vibrate and the image recorded on the film may be blurred. You can put your elbow on your body, or put the camera on a solid and stable object, such as a tripod, knees, or leaning against a post or wall. Especially when the shutter speed is low, it is best to find a support point, otherwise it is difficult to get a clear result.

When using a tripod, you must not be careless. After putting the camera on a portable tripod, it is often top-heavy and may fall over when it is windy. People may trip when they walk by. Therefore, people should never leave the camera. It should be noted that when the vehicle passing near the tripod vibrates greatly, the image will be unclear.

Also, don't hold the zoom head in your hand, because the lens moves back and forth when zooming!

Fingers and hair, camera straps and other things should not touch the lens, autofocus window, sensor window, flash, etc. You should not stand in front of these parts, because it will block a part of the photo and make it impossible to record the image, and it will also dirty the lens, thus affecting the clarity of the image in the photo.

Camera lens blocked-photo sketch

Attention should be paid to the adaptability of human eyes during photography.

Instantaneous exposure leaves all kinds of things, and there are thousands of words between square inches. Almost everyone wants to keep beautiful moments with their own cameras. However, some friends may have noticed that on some occasions, we seem to feel the light is very bright, but the images we can shoot are quite dark. Some scenery, bright and dazzling to people's eyes, can't be recognized when shooting on the screen. Why is this?

Anyone who has taken photos knows that picturesque scenery and colorful moving objects are recorded on photographic film after passing through the camera lens, which is purely a physical and chemical process. However, our visual experience is not so simple, because the physiological function of the human eye is at work, as well as the memory function and psychological factors. Therefore, the feeling of scenery is not as "objective" as that of movies. This characteristic of human vision is called "visual adaptation". People often turn a blind eye to this "visual adaptation", which leads to photography mistakes in some cases.

"Visual adaptation" is manifested in many aspects.

The first performance is "full brightness adaptation". For example, when people walk into the room from the outside, they often feel that the indoor scenery is as bright as the outdoor scenery. However, if you shoot indoor scenery with the same aperture and exposure time as outdoor shooting, you will find that indoor photos will look dirty and dark because of underexposure. This is because when people enter the room, the low indoor illumination will enlarge the pupil of the human eye and improve the sensitivity, thus doubling the amount of light entering the human eye, sometimes up to ten times, so they will not be aware of the change of illumination. This is the human eye? Quot brightness is fully adapted. "However, film does not have such an adjustment function. Therefore, from the perspective of photography, due to the wide adjustment range of human eyes, it is often impossible to correctly estimate the actual light intensity, which is not good for photography. The solution is to measure light with an exposure meter before pressing the shutter, and make necessary adjustments to the aperture and speed of the camera to compensate for the "brightness adaptation" that the film does not have.

Correspondingly, the feeling of color also has the phenomenon of "full adaptation of color vision". For different lighting conditions such as sunshine and light, sunny and cloudy days, morning and dusk, although the spectral components of the light source have changed, people can't see how much the color of the object has changed because of the self-adjusting function of the sensitivity of the photoreceptor cells on the retina of human eyes. In addition, people can remember the color of objects under white light. Therefore, when the light source changes, people are not aware of the color change of the object due to psychological effects. At this time, it must be remembered that film does not have such adaptability. Therefore, different types of thin films or corresponding filters should be selected according to different light sources. Otherwise. There will be different color casts.

Another manifestation of visual adaptation is "local brightness adaptation". For example, there is a fairly bright object in the field of vision. Staring at it for a long time will reduce the sensitivity of this part of the retina because of fatigue. When we move our eyes to another light-colored reflective surface, we will leave a "afterimage" of a dark object. On the contrary, when we look at a black object and move our eyes to another light reflective surface, we will see a white object. Quot afterimage ". As the sensitivity is adjusted again, the afterimage will gradually disappear. If you stare at a colored object for a long time, when you turn your eyes to another plane, you will produce a "afterimage" with the opposite color of the object. For example, if you stare at a red object, the residual image left behind is almost cyan. This phenomenon is called "local adaptation of color vision" and "color afterimage".

The practical significance of understanding this adaptation is that if you stare at a picture for a long time and then observe the next picture, the "residual image" of the previous picture will be superimposed on the next picture, which will have an impact on its brightness and color. This has both advantages and disadvantages. Before the second picture appears, displaying the complementary colors in the previous picture will make the colors in the second picture more vivid. When correcting the color of a photo, you should try to avoid staring at a picture for a long time to prevent the sensitivity from decreasing and the color from being misjudged due to visual fatigue.

The third visual adaptation is called "lateral adaptation". In color photography, we should also pay attention to the "lateral adaptation" of vision. In the picture, if the brightness or color of adjacent areas are different, the sensitivity adjustment of photoreceptor cells in different parts of human retina will change vision. The rule is that bright objects appear brighter on a dark background, and dark objects appear darker on a bright background (see figure 1). The color of the foreground object will change to the complementary color of the background. See figures 2, 3 and 4. Figure 1 shows the normal skin color of human face, and Figure 2 shows the skin color of human face on a red background. Obviously, the skin color is biased towards the complementary color of red and cyan; In fig. 3, on the blue background, the color of human face is biased towards blue and yellow complementary colors. Therefore, when shooting portraits, we must consciously pay attention to the influence of background color on human face skin color.

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