Diving knowledge photography

Q: Organize an underwater photography activity. If you have no diving experience, how long does it take to train?

Answer: If you want to take underwater photography, you must first learn the level of two-star divers and master considerable diving skills and experience, and then learn underwater photography. The whole diving course takes 5-6 days, and the experience of diving more than 30 bottles of gas in the sea is the basis for learning underwater photography well. The use of camera waterproof cover can be mastered in a few hours. If you want to take good photos underwater, you must master diving skills and understand underwater photography.

The only place suitable for underwater photography in Beijing is the Aquarium, but the number of people can't be large, 3-4 people at a time. And the aquarium can only be used for practice when you are just getting started. If you want to shoot more things and master shooting under different conditions, you still have to go to Sanya and other sea areas.

Q: The relationship between underwater photography and diving technology.

A: To start underwater photography, you need to learn safe underwater activities first, that is, learn diving first, and then learn underwater photography. The higher the diving technology, the deeper the understanding of the ocean, underwater environment and biology. It is also possible to take good photos. But it needs to be clear that underwater photography is much more difficult and complicated than on land, and it needs a long time of study and exploration.

Underwater photography technology is endless. If a standard must be set, then the diving technology is at least equivalent to the level of Samsung divers. But just like landscape photography, this is just an introduction. The level of underwater photography in the future depends on personal understanding, artistic accomplishment, inspiration and other factors.

Q: What other functions does the waterproof cover of digital camera have besides underwater photography?

A: Take the Olympus digital camera in 2003 as an example. All models of digital cameras are equipped with corresponding waterproof covers. Each waterproof sleeve can operate all the functions of the corresponding camera. At the same time, some cameras are also equipped with underwater color temperature balance function and life waterproof function. It allows you to take photos at will in various sports and various harsh environments.

The waterproof cover is small in size, light in weight, easy to carry and easy to operate. It is not only waterproof, but also excellent in dustproof performance. It is also suitable for skiing, rafting, upstream, boating, rock climbing, mountain climbing (snow-capped mountains), outdoor crossing (rainforest desert) and other outdoor sports. It has long been a standard outdoor equipment abroad.

Q: How to choose underwater photographic equipment and what should I pay attention to when buying it?

A: When you choose to buy a digital camera or video camera, you should first know in detail whether there is a waterproof cover of the corresponding model. When purchasing waterproof covers, be sure to confirm whether the buyer has trained in the use of waterproof covers and whether the after-sales maintenance is perfect, such as whether the after-sales service can be carried out at the place of purchase.

Every waterproof sleeve is put on the market after passing through high voltage test, and it will not leak underwater unless it is used improperly or accidentally. In order to avoid damage to your equipment, please be sure to attend the corresponding training after purchase and join the corresponding property insurance.

Photographic equipment and waterproof covers are very expensive. From several thousand yuan to hundreds of thousands and hundreds of thousands, the price of professional grade is even as high as millions. Therefore, when purchasing, you must fully negotiate with professionals or manufacturers before purchasing. There are many smuggled diving equipment and waterproof cover products in Chinese mainland. Please note whether the seller is responsible for after-sales maintenance, equipment insurance and technical training.

The waterproof ability of ordinary waterproof cover can reach 40 meters.

(1) Price and weight: With the development of digital cameras, the size of cameras has been greatly reduced, and waterproof accessories have also developed from traditional metal protective cases to plastic waterproof cases directly manufactured by camera manufacturers, which can generally withstand a waterproof depth of 40 meters. For example, the recently purchased 5 megapixel camera with waterproof case only costs about HK$ 2,500 and weighs less than 65,438+0 pounds. Regardless of the price and weight, it is equal to one part of the unified transmission package 10.

(2) Sensitivity and storage capacity: Digital camera technology is several times more sensitive to light than traditional film. This can reduce the exposure limit of traditional film under water due to the weakening of light intensity. Digital storage technology can effectively reduce the cost of photography and improve space efficiency.

(3) Post-production: Because the density of water is higher than that of air, luminosity and color disappear with depth. Traditional film has low sensitivity, and it is difficult for photographers to control its color because it is developed mechanically. Nowadays, with the development of science and technology, various easy-to-use editing software is provided on the market, which is convenient for us to adjust the related luminosity and chromatic aberration according to our personal preferences. You can also output through different media, including computers, televisions and even printers. You can master all the procedures by yourself and increase the satisfaction of photography.

With the development of digital cameras, underwater photography has become popular. However, no matter what kind of camera and equipment are used, what is a good underwater photo? Although photography is very personal, beauty is also a subjective feeling. But in general, if the focus and exposure are accurate, the light source and contrast are average, and the subject is distinct, this picture is very prominent.

How much does neutral buoyancy affect photography?

(a) The camera can be stabilized, especially for slow shooting;

(2) Reduce the chances of stirring seabed sediments and sand grains and affecting the photo structure;

(3) Reduce the chance of destroying coral and even avoid injury;

(4) It helps to reduce fuel consumption. I have seen some divers lose their breath because of ecstasy. Although it didn't lead to more injuries in the end, I can imagine the embarrassing scene at that time. Moreover, if not handled properly, it may lead to tragic results.

On neutral buoyancy

For an object placed in water, the buoyancy it receives is equal to the weight of the water it displaces. If the weight of water displaced by an object in water is greater than the weight of the object itself, the object will float on the water surface, which is called positive buoyancy. Conversely, sinking is called negative buoyancy. If the weight of the water discharged by an object is equal to the weight of the object itself, the object will be suspended in the water to achieve neutral buoyancy.

When diving, it is very important to learn to control the buoyancy on the surface and bottom. For example, when resting on the water, positive buoyancy can save physical strength, while when underwater, you need to maintain neutral buoyancy most of the time, so that you can swim freely in the water, maintain good visibility and avoid hurting you and fragile creatures in the water.

Divers can adjust buoyancy by counterweight, buoyancy control device (BC) and breathing depth.

How to improve neutral buoyancy skills? Of course, it's not difficult. It should be pointed out that:

(1) Everything starts with slow motion, which is much more resistant to air and water. Slow motion is the most effective way to save gas, at the same time, it can also reduce the degree of scaring the creatures, keep the natural shape of the creatures, and get closer to the subjects to get the best shooting position and angle;

(2) The airway is well controlled, slow and deep. Under water, inhalation and exhalation will affect buoyancy, leading to unstable holding of water. Slow motion can reduce the demand for oxygen and the airway is easy to control. When shooting, after handling the camera settings and composition, you can shield a proper amount of air before pressing the shutter, which is helpful to the stability of shooting;

(3) When swimming, it is best to bend the calf slightly upward to avoid the frog shoes touching the coral, and also to avoid the force generated by the frog shoes stirring the seabed and affecting the shooting effect;

(4) When shooting close-up, you can use the fulcrum suspension technology to stabilize your body. Of course, we must first examine the surrounding environment, and pay special attention to the possibility that corals may be damaged or injured below us. If necessary, you can touch the stone surface with one finger to keep balance. It is absolutely necessary to note that most of the creatures on the seabed have a strong desire to protect, and touching them casually will lead to a lose-lose situation at any time;

(5) Current will affect the stability of blasting. It is unwise to deliberately sail against the current for filming. If you encounter a large current, you are more likely to force your hand beyond your ability. It is wise to give up shooting, keep balance and protect the camera. Finally, it is a diver's habit to check the depth and pressure gauge frequently.

When we master the buoyancy control process at will, the process of shooting composition will become easy and handy. Undeniably, the color of light will gradually disappear due to the water depth, and the visual field is short when the depth or water surface is chaotic, which makes underwater shooting have many restrictions. Therefore, in order to achieve the best shooting effect, it is necessary to use diving technology to make the camera and the subject reach the nearest distance under a given composition, so as to obtain the best light source and color reflection effect.

Causes and improvement methods of common image quality problems in underwater photography

This paper analyzes the common image quality problems in underwater photography and their causes, and puts forward some improvement methods for these problems. Underwater photography (including underwater photography and underwater photography) is one of the commonly used underwater detection methods in marine engineering. Compared with other methods to detect the surface state of objects, such as visual inspection by divers, touch inspection and so on. It has the characteristics of authenticity and reliability, real-time observation on water and permanent data preservation, and is widely used in underwater structure detection of ships, oil platforms, docks, dams and other facilities.

Because of its application in water, many problems caused by it have great influence on underwater photography. In addition to solving a series of problems such as sealing, pressure resistance, anti-corrosion and electrical insulation of underwater photographic equipment, in practical application, we should also seriously study and solve the adverse effects of light scattering, refraction and absorption in water, buoyancy of water and impulse of water flow on underwater photographic imaging quality. According to the diver's underwater photography practice for many years, we feel that the common image quality problems in underwater photography mainly include three aspects: first, the image is blurred; Second, the framing is inaccurate or the picture is unstable; Third, the color image is blue. This paper analyzes the main causes of these problems and puts forward some solutions.

Causes and improvement methods of 1 image blur

Blurred underwater photos or TV images are the most common and serious image quality problems that affect the detection effect. There are many reasons for image blur, but no matter what the reason is, it needs to be overcome in practical application to ensure good photographic effect.

1. 1 The scattering of water reduces the clarity of the image.

There are many reasons for image blurring, but the main reason is the low transparency of water and the high content of tiny inorganic and organic particles in water. When shooting in this turbid water, because of the scattering effect of these tiny particles on light, whether underwater photography or underwater photography, the imaging effect is like "seeing flowers in the fog", which is blurred.

Judging from the application and development of optical imaging technology, it is difficult to fundamentally solve this problem at present. The following methods can be considered to improve the actual underwater shooting.

(1) Choose a water area with high transparency or a shooting opportunity. Usually, the working water area of underwater photography cannot be freely selected by the operator. However, in some cases, such as the nearby waters with high transparency and high image quality requirements, if conditions permit, the subject can be transferred to the waters with good water quality for shooting. In addition, even in the same water area, with the changes of tide, water flow and weather, the transparency of water will change. As long as the operator pays attention to observing and accumulating data and chooses a time with relatively high transparency, the shooting effect will be improved.

(2) use close-range shooting. Under the same shooting conditions, the closer the underwater camera or video camera is to the photographed object, the smaller the scattering effect of water on the light transmission process in water, and the clearer the photographed image. Therefore, in underwater photography, as long as the shooting requirements can be met, the shooting distance should be as close as possible.

According to the experience, usually the underwater shooting distance should not exceed 1/2 ~ 1/3 of the water transparency. The transparency of water can be roughly measured by the disk method. However, it should be noted that the actual minimum shooting distance cannot be less than the nearest shooting distance of the camera lens, otherwise the image will be blurred due to the inability to focus. For example, the minimum shooting distance of 35mm standard lens of Nikon OS-V underwater camera should not be less than 0.8m, and the minimum shooting distance of Nikon 28mm lens should not be less than 0.6m.. ..

(3) Use special muddy water underwater camera or muddy water photography auxiliary device. In this camera or device, a pressure-resistant or non-pressure-resistant photographic cover is installed in front of the camera lens, and the medium in the closed cavity in the cover is air or clear water. In this way, the path of light is shortened in the process of transmitting from the object to the lens in the muddy water, thus reducing the scattering effect of water and improving the clarity of the image. However, due to the limited length of this camera cover, the improvement effect is obvious only when shooting at close range.

(4) Underwater lighting uses oblique light instead of smooth light. Under the same shooting conditions, the different illumination directions of light sources have certain influence on the clarity of images. When the illumination direction of the light source and the shooting direction of the lens are in the same direction (that is, the light direction), the particles in the water in front of the lens have a great influence on the image clarity; When the illumination direction of the light source and the shooting direction of the lens form an included angle of 30 ~ 60 (that is, oblique light), the definition of the image will be better. Therefore, when underwater lighting, the lighting lamp should keep a certain distance from the camera or video camera to form oblique lighting.

(5) In the process of underwater shooting, prevent water turbidity. Especially when shooting underwater, divers move their positions or hit their fins, which will easily muddy the water and affect the shooting effect. Pay special attention to this before shooting. Generally shooting underwater, divers can wear work shoes instead of fins. When there is a current, divers should shoot in the direction of top current or side current.

1.2 Due to the shaking of the underwater camera, the image clarity is reduced.

Because of the buoyancy of water, current and swell, it is often difficult for divers to hold the camera steady when taking pictures underwater, which leads to blurred photos taken underwater.

To solve this problem, we must first improve divers' diving skills and ensure that they can control their stability in a more complicated underwater environment. In addition, the following methods can be considered to solve the problem.

(1) Build an auxiliary operation platform as a support for underwater shooting. When shooting underwater, especially in the case of large current and complex sea conditions, it is very effective to arrange a working platform for the working diver as a support to stabilize his body and camera, which can prevent the image from blurring caused by camera shake.

The working platform can be made by itself according to the actual situation of the working object, position and scope. Platforms can be varied, such as hanging baskets welded with steel pipes, diving ladders, decompression racks, etc. Sometimes you can tie a hemp rope on the job site as a support for divers, such as tying a submarine cable.

(2) Divers have correct shooting posture and can hold their breath when pressing the shutter. Divers should choose a good shooting posture according to the different shooting objects and positions. When shooting underwater, if the water flow is not big, you can choose to shoot in a kneeling position with two legs or one leg, which has good stability; If the water flow is large, you can choose to shoot in prone position. If you have a work platform, you can also adopt the above posture. It is difficult to shoot in floating or swimming posture, and it is generally only used in the case of no water flow and no swell.

(3) Wear heavy objects when shooting underwater. When shooting underwater, in order to increase the stability of divers, you can wear lead pressure, which is generally not less than 15 kg, and if you wear a diving suit, it should be not less than 15kg. However, these lead weights should not be worn at one time, nor should they be worn too much when shooting or swimming in suspension, otherwise it will bring danger to divers due to excessive negative buoyancy. Lead pressing can be divided into two groups. One group put on the normal diving weight. After the diver touches the bottom, the second group of lead will be sent down by the water surface, and the diver will tie it or press it on his leg.

1.3 Inaccurate focusing will reduce the image definition.

In underwater photography, with the change of shooting distance, it is necessary to focus the subject accurately. Improper or out-of-focus will lead to blurred images.

At present, the focus of the underwater camera of the commonly used diver underwater TV system is mostly controlled by the water console. During underwater shooting, the operator of the water console must concentrate on the image on the monitor. When the camera moves, the operator should first quickly judge whether the shooting distance is getting closer or farther, and then control the focus switch to track the focus in time and quickly according to the speed of distance change. When the shooting distance changes slowly, you can use the method of "inching" to focus, and when it changes quickly, you can use the method of "linkage" to focus. Divers should pay attention to the cooperation with the water surface when operating the camera underwater, and try to keep a relatively stable shooting distance so that the console operator can't track and focus.

If necessary and conditions permit, it can be previewed before the actual shooting, so that the cooperation between the operator and the diver is more tacit, and the timing and speed of focusing can be better grasped.

For underwater cameras without focus indicator or autofocus function, such as Nokonos-V underwater camera, the shooting distance should be accurately estimated and the focus button should be adjusted correctly before shooting. If the shooting requirements are high, the accurate shooting distance can be determined by measurement, but it should be noted that the distance measured by the meter ruler is multiplied by 3/4 and converted into "underwater distance". When an underwater camera equipped with a focus indicator focuses underwater, it may be difficult to adjust it due to dim light or turbid water, so it should be carefully adjusted and then checked by the method of line-of-sight estimation. For cameras with autofocus function, when focusing underwater, the subject must be placed in the automatic ranging area displayed by the viewfinder to prevent inaccurate ranging.

In addition, using wide-angle lens and small aperture can increase the depth of field, and using large depth of field in underwater photography can make up for the image blur caused by inaccurate focusing. When shooting underwater, divers should also ensure that the minimum shooting distance is not less than the nearest focusing distance of the lens.

1.4 The image cannot be recognized due to serious underexposure or overexposure.

Underwater photography usually needs auxiliary lighting to provide enough lighting for shooting. Underwater photography uses underwater lighting, and underwater photography generally uses underwater electronic flash. However, if the auxiliary lighting equipment is improperly used and the illumination of the light source is seriously insufficient or too strong, the photographed image will be dim or bright, and the photographed object cannot be identified.

When using flash to take underwater photos, first of all, adjust the aperture coefficient correctly according to the flash index and shooting distance, and don't forget to readjust the aperture coefficient when the shooting distance changes, and also prevent the shooting distance from exceeding the effective range of flash; Second, wait until the flash is fully charged. When the flash indicator lights up, it can usually only be charged to about 70% of the full charge. Don't shoot right now, wait a few seconds before pressing the shutter.

Generally, the brightness of the illuminating lamp equipped with an underwater camera can be adjusted. When taking underwater photos, the appropriate brightness should be adjusted according to the image display of the monitor and the reflective intensity of the scene surface. When shooting at close range, it is necessary to adjust the illumination direction of the lighting lamp to avoid strong reflection on the scene surface and leaving bright spots on the image.

In addition to the above reasons, there are other factors that will also affect the clarity of the image, such as ropes, bubbles, seaweed and other objects between the lens and the scene, which are not removed in time when shooting, resulting in partial occlusion of the image; When shooting a moving object, the shutter speed is too slow, which leads to the blur of "motion"; When the camera zooms from a short focal length to a long focal length, the focus is inaccurate.

2. Causes of inaccurate framing or unstable picture and improvement methods.

Inaccurate framing composition or unstable picture is also one of the common problems in underwater photography. Inaccurate framing will cause the required scene to be shot incompletely or incompletely, and the unstable picture will make it difficult for the surface personnel to see the image of the monitor clearly, which will affect the effect of underwater detection.

2. 1 camera or camera displacement leads to inaccurate framing and composition.

When divers shoot underwater, if the camera or video camera is unstable, it will not only blur the image, but also change the shooting scene because of the shaking of the lens, resulting in inaccurate framing of the taken photos or TV images. The key to solve this problem is to keep the fuselage, camera and video camera stable when shooting. See "1.2" for details.

In underwater photography, when the shutter is pressed, the diver holds his breath, which can better keep the camera stable.

2.2 The camera shake causes the picture to be unstable.

Because of the buoyancy of water, current and swell, it is often difficult for divers to hold the camera steady underwater, which leads to the image jitter taken underwater. To solve this problem, we must first improve divers' diving skills and ensure that they can control their stability in a more complicated underwater environment. In addition, we can refer to the method in "1.2" to solve the stability problem.

When pushing, pulling or shaking the lens, keep your body steady and don't jump. When pushing in or pulling out, you should move or swim slowly and in small steps. Generally speaking, the method of pushing in the lens is more stable than the method of pulling out. When shooting horizontally, the method of moving to the side of the subject slowly and in small steps is adopted, and the shooting effect is good. When there is water flow or suspension shooting, it is best to lay a guiding action rope so that divers can move and shoot with the help of the action rope.

2.3 Did not grasp the relationship between the scene and the shooting distance, resulting in inaccurate framing and composition.

The underwater camera or camera lens has different viewing angles, so the scenes shot at different shooting distances are also different. Some divers can't master and use this relationship well, and the shooting distance is not properly controlled, which leads to unqualified shooting scenes and inaccurate framing.

To solve this problem, it is mainly to grasp the relationship between lens angle and shooting scene and scene. Scene refers to the size of the picture taken by the lens at a certain distance, and the size of the scene mainly depends on the size of the lens angle of view. Scenery refers to the scale of the same scene displayed on the screen. The commonly used scenes in underwater photography include panoramic view, middle view and close view. The size of the scene mainly depends on the size of the scene and the size of the scene.

For example, when the underwater viewing angle of the 35mm lens of Nikon OS-V camera is 46.5 and the shooting distance is 1.5 m, the scene (width× height) is 0.84×0.56 (m) and the scene is 1.26×0.8 1.05(m). Therefore, when shooting people in the form of banners, the shooting distance is1m. At the shooting distance of 1.5 m, the close shot of people above the chest and the middle shot of people above the waist can be taken. To shoot the panoramic view of standing people, the shooting distance must be above 3.6 meters. Based on this relationship, divers can estimate the appropriate shooting distance according to the size of underwater objects and the requirements of shooting scenes, and take photos that meet the requirements.

For an underwater camera without a camera, we should not only grasp the above relationship, but also pay attention to the orientation of the camera lens to avoid the phenomenon that we want to shoot the "head" but the "thigh". According to experience, we can usually aim at the center of the subject along the upper edge of the camera shell to ensure the accuracy of framing. In addition, a simple frame viewfinder can be made according to the size of the lens angle of view and installed on the camera.

Under the condition of telephone communication, it is a very effective method for divers to adjust the orientation of the lens by telephone according to the display of TV images.

In addition to the above reasons, the framing composition will be inaccurate, and the parallax between the framing range of the viewfinder and the actual shooting range of the lens with different focal lengths will cause the framing composition to be inaccurate. In practical use, different additional viewfinders should be used according to lenses with different focal lengths. In addition, when shooting a moving object, the push of pressing the shutter is not determined according to the moving speed of the moving object, which will also lead to inaccurate framing composition.

Causes of blue image and its improvement methods

As we know, sunlight is a kind of composite light, which consists of seven monochromatic lights with different wavelengths: red, orange, yellow, green, cyan, blue and purple. In the process of light propagation in water, the intensity will gradually weaken due to the absorption of water, and this absorption of light by water is related to the wavelength of monochromatic light. Generally speaking, water absorbs red and orange light most seriously, followed by yellow, purple and green light, and blue and cyan light is the weakest. So the light we see underwater is usually blue-green, and the water near the shore or river turns yellow-green because it contains a lot of green marine life and sediments. Therefore, the photos and TV images taken by underwater color photography tend to be Lan Qing or blue-green. Moreover, with the increase of light transmission distance and water depth in water, this color shift becomes more and more serious.

Generally speaking, when underwater photography is used in underwater engineering, the color deviation of photos or images does not affect the technicians' identification of the photographed objects. However, in the case of underwater detection which requires high image color, some measures should be taken to reduce or correct the color deviation. The commonly used methods are as follows.

(1) Shorten the shooting distance. The closer the shooting distance, the shorter the light transmission distance between the scene and the lens, and the less color cast. Therefore, underwater photography can shorten the shooting distance as much as possible, which can not only improve the clarity of the image, but also reduce the color cast.

(2) Add red transparent paper in front of underwater lighting or underwater flash. Adding red light to the lighting lamp can make up for the reduction of red light caused by water absorption, thus correcting the blue phenomenon to some extent.

This is a very effective way to correct the blue color. However, it should be noted that adding red transparent paper in front of the underwater flash will reduce the light intensity output by the flash, so exposure compensation is needed, otherwise there will be underexposure.

(3) Add a warm color filter or warm color transparent paper in front of the camera. The function of this method is basically the same as adding red transparent paper in front of underwater lighting or underwater flash, except that the color of color filter or transparent paper should be orange instead of red, otherwise it may "overcorrect" and make the image red.

The above is just the author's superficial discussion on several quality problems that often appear in underwater photography and their improvement methods. In addition, there are many problems that need to be further studied, and there are many better ways to improve them. This article introduces jade here, please correct me if it is inappropriate.