Schlieren photography technology

Lighting has two functions in photography:

One is "lighting", the key point is to brighten the environment so that the camera can take pictures. One is the "element", where light plays a role in the picture environment, including artistry and the language of the picture. So, please remember that lighting is not just "lighting", it is not only lighting, but also showing meaning. For news photography, lighting is the most easily overlooked. The general press will say: the news is so urgent, there are pictures, and the color is not too bad. Who has time to pay attention to the lights! -indeed, this statement can't be wrong. Many times, we ask for "taking photos" first, and then ask for something else. The lighting is good, which is already the level of "beauty". However, a real "photographer" is not allowed to give up "perfection" Moreover, it is not enough for a photojournalist to "grab the news" forever. There are always opportunities to shoot special topics, support programs, and even become a director or director one day after accumulating enough experience. Therefore, the knowledge of lighting can be unprofessional, but it is necessary to know some basics.

Color temperature one

When it comes to light, we must explain the problem of color temperature. Most people who play with cameras know the thing "color temperature" more or less, but they may know a little about the principle of color temperature, but they don't know why. The fact is that as long as you have read junior high school physics, you must remember something called "absolute temperature", also called "Kelvin temperature". Where 0 K is absolutely zero, which is exactly -273℃, does the example that 20℃ is above 20+273 = 293 K remind you? ! The color temperature of 3200K refers to the "light color" emitted by the laboratory blackbody at a high temperature of 3200 K (2927℃), where K stands for absolute degree-day. When the color temperature is 3200K, the light color is close to red. I remember that when iron burns above 1000 degrees, it is the time when it burns red and shines! As the red iron heats up, the light will get brighter and closer to white. If you can control it not to melt and spread, you will find that the light will get closer and closer to blue (just like the blue emitted by gas fire). Close to red light, with low color temperature, long wavelength and long transmission distance per unit line, it is easy to be absorbed, so red light is often used as a warning light. Close to blue light, high color temperature, short wave length, short unit linear transmission distance, easy to be reflected, the sky is blue, the sea is blue, all because blue is reflected and red is absorbed, so we can't see it. If the inertia is opposite, then our sky and ocean will be red.

Color temperature two

Human's perception of color comes from light and its reflection. After the light enters the eyes, it can distinguish various colors through the feeling of the optic nerve. Because the human eye has the function of automatic adjustment, we can still distinguish the color difference of the object even under different light sources, so the color of the object seen under 3200K tungsten filament light is not much different from that seen under 5000K sunlight. The camera or negative reflects the color ratio (tricolor or tricolor ratio) of light by electronic or chemical beam splitting, and the machine can't automatically adjust the color difference, so the recorded color is completely reflected. So what we see when shooting in light is normal color, but if we don't adjust the sensitivity of the machine to color temperature, we will find that the whole color is wrong when shooting in the sun, the red series is not obvious, and the whole picture is "blue". Similarly, if you see a normal color when shooting in the sun, and the sensitivity of the machine to the color temperature has not been adjusted, then when you shoot an object under the light, you will see a "red" picture with less blue series. This kind of situation is often encountered when we shoot ENG. When shooting in indoor lighting environment, sometimes we bring the sunlight in through the window, and we will find that the sunlight is blue, but what the naked eye sees is normal. Therefore, before shooting with ENG, we must do a good job of "white balance" and make a "zero" action with "white" as the standard, so that the camera can take the "color" of white objects (usually white paper) as the standard white under the light source of the scene, so that other colors can have a standard to follow, and the camera can

Color temperature three

For professional cameras, the standard of color temperature is quite high, so most of them will have more than two color temperature panels (3200K and 5600K), and even broadcast cameras will have more than four segments (3200K, 4500K, 5600K and 6300K). The finer the subdivision, the higher the accuracy and the lower the relative tolerance. Therefore, when using advanced cameras, in fact, the more sophisticated the machine, the more beautiful the photos will be, but the greater the chance of making mistakes.

Fortunately, however, technology has been improving. At present, the new generation of digital cameras control the color temperature more and more accurately than before. Maybe one day, "dialogue" will become redundant work, and then very advanced machines will be needed to "manually" adjust the color temperature! Aren't many cameras like this now? Only advanced models can focus manually and adjust the aperture manually. Sometimes, the color temperature can be used to create different images. For example, deliberately being blue can show a cold tonality, and deliberately being red can show a warm feeling; On the same screen, you can even have three different color temperatures: red, blue and standard to show the artistic sense in the image ... but I have to remind you that you must have a full understanding of the "color temperature" before playing with the color temperature, and you can play with the color temperature with control skills. After all, some things can only be used after you have accumulated experience, otherwise you will be black and blue before you learn to fly like others.

Color temperature four

In addition, let me mention to you first that there is a kind of "colored light" that often confuses beginners with color temperature. Colored light refers to the use of special lighting colored paper or color plates in front of lamps to produce "colored light". Most of this light is used for "effect light" and "atmosphere light" to create special effects of shooting scenes. This kind of colored paper has red, orange, yellow, green, blue, indigo and purple ... all kinds of colors. Of course, the typed light will also affect the color temperature value, but please note that the effect light belongs to "ambient light", which is different from the use of "illumination light" required for shooting. Ambient light is more like the color on the wall, so the original color of "light" should be faithfully presented on the screen. When shooting, the red one should be red and the yellow one should be yellow. If you talk under the yellow effect light, if you can correspond to an excellent temperature (maybe within one or two thousand degrees), you will find that the picture you shot has no feeling of yellow effect light, and the white paper under the yellow effect light should be yellow. Therefore, when encountering the above situation, we must first decide what kind of color temperature is the main color of "lighting light" (generally, the standard color temperature of 3200K is the main color, but there is also the sunshine color temperature of 5600K as the benchmark), and then set the camera to this benchmark value before adding colored paper to play the effect light. The above situation is the most prone to mistakes when shooting with stage lighting, especially when a lot of artistic colors are needed to present the atmosphere, such as stage plays and dance performances. Many people will take white paper to find the brightest light source to "talk", but the color of the picture they see after shooting is very different from that seen on the spot ... If you use a home camera with "automatic white balance" or some professional models with "AWB" automatic dialogue function, you will find shooting. There is no reason, because the function of automatic dialogue is the same as "automatic aperture". The machine captures a certain range of light to calculate the "average color temperature". If the light source changes constantly, the natural color temperature value will also move with it. The solution is actually very simple. Most machines are set to the preset "lighting" (3200K), and then they can shoot. Because most of the stage is illuminated by lights with a standard color temperature of 3200K, this can be used as a reference value and can show appropriate colors. Of course, some people will use other color temperature values for lighting in some special occasions (such as sunshine 5600K), but there are not many opportunities! If you can judge, you can also try to adjust the color temperature control of the machine to see. ENG shooting is much easier now. The machine has the function of "dialogue". Film cameras and TV cameras before ancient times had no dialogue function. If there is a problem with color temperature when shooting on location, it will not be so easy. You need to use a color temperature meter, which is very similar to the photometer used for taking pictures. After measuring the temperature of the main light source, you need to find the corresponding "color temperature lens" to hang in front of the camera to change the color temperature value. If you forget to convert in a hurry or make a mistake in calculation, the shot back can be ... (The film can also be darkened and decorated during development, and the video will be miserable! )

The stronger and sharper the light, the more obvious the shadow, and the greater the brightness contrast and contrast.

Lighting: sub-light

Auxiliary light is also called fill light, and most of the fill light will be softer than the main light, so as not to rob the role of the main light. In some occasions where the shadow effect is deliberately created, the fill light will be deliberately weakened or even not filled.

Lighting: Backlight

Or "reflection" or "contour light", which stands on the back of the subject, can avoid the place where the camera shoots, so as to outline the outline of the subject and create a sense of space and three-dimensional sense between the subject and the background. There are also people who stand above the subject and do "light" or do "face light" below (if the subject is a person).

Lighting: effect light

Sometimes, for the beauty of the picture, some lighting effects will be created, such as curtain lighting, color halo, water lines, neon effect outside the window, lightning and so on. These special effects are called effect light or ambient light. The erection location of effect light is not limited, mainly depending on what effect it wants to present. Sometimes we have to adjust the position of the main light and the supplementary light for a certain effect, so as to correct the best effect. Generally speaking, in actual use, the number of lamps can almost determine the quality of the picture, but in fact, whether it is a single lamp or a dozen lamps, as long as they are used properly, they can produce good results.

Lighting: single lamp

Most people will put the light directly within 30 degrees behind the camera. When the light is projected on the object, you can adjust the angle and height of the lamp to avoid unnatural shadows as much as possible. (Of course, sometimes shadows are deliberately created. This is another matter. If the brightness is too strong, the light is too sharp.

Most photographic lamps can fine-tune the focal length of light, so that light can be concentrated or diffused. Some cameras have a "headlight" installed above the lens, so that the light produced is "flat". At the same time, if the person is photographed, his eyes will be unnatural because of the direct light when facing the camera. You can add a "soft light sheet" in front of the lamp, or move the lamp slightly to avoid direct exposure to human eyes. Of course, headlights are generally not too bright. Without lighting, most of their functions are rarely used. It's okay to shoot news, but it's irresponsible to shoot with headlights if you want to do a special topic or program! In fact, sometimes natural light sources can be used as "main light" and headlights can be used as "supplementary light", which means that there are two lights, and the picture quality will be better.