The English scientific name of flash light is Flash Light.Flash is also enhancedExposureOne of the best ways to do this, especially in dim places, is to flash to help make the scene brighter.
The full Chinese name is“Electronic flash lamp”, also known as high-speed flash.The electronic flash lamp stores high-voltage electricity through a capacitor,pulseTrigger to discharge the flash tube and complete the flash.The color temperature of the common electronic flash lamp is about 5500K, which is close to theColor temperatureThe luminescent property belongs to the cold light type, which is suitable for photographing objects that are afraid of heat.
Flash light can emit very strong light in a very short time. It is photographyphotosensitivePhotography accessories.It is mainly used for instantaneous illumination in dark places, and also used for the shooting of objects in bright placesLocal fill light。Compact shape, safe use, convenient carrying and stable performance.
Development history
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Photography came into being 48 years after its birth (1887)flash photography Its development process is as follows:
1. Magnesium powder flash machine (1887~1930).Ignite magnesium powder andPotassium chlorateThe mixture emits strong white light, and this method has lasted for nearly half a century.
2. One shot flash (flash bulb).German in 1929Ernst Mayer(J. Ostermeyer).
threeElectronic flash lamp。It was invented in 1931 and sold in 1939. It uses the principle of gas discharge.It is characterized by high speed, economy and convenience, and is mainly divided into three generations of products:
The first generation product was used from 1931 to 1939. It uses a mechanical oscillator, which is prone to failure.
The second generation product was used in the mid-1960s, and it uses transistor oscillation circuit.Such as seagull 107B, 108
The third generation product was put into the market in 1972, and its characteristics are:
(1) AdoptIntegrated circuitThe photosensitive control circuit composed with the blue silicon transistor can automatically control the lighting time (from 1/50000 to 1/120 seconds) according to the shooting distance and the intensity of the reflection
(2) Change bypass type to parallel control typeElectronic flash lampTo store energy, save electric energy, shorten flash gap, and create conditions for stroboscopic.
(3) Adopt“Hot boots”And another automatic contact to control the speed to "X" position.
LED lightning series HD intelligent digital flash lamp (industrial grade, model ZS-LEDSGD-1) Continental Optoelectronics focuses on the field of intelligent transportation, developed for various capture systems, such as security checkpoints, overspeed capture, red light running, etcE-policeThe new high-power high-performance digital pulse LED flash lamp is developed according to the working environment and functional requirements.This product adopts a unique digital control circuit, which has the characteristics of fast return and long life, accurate control of flash time, continuous output in the form of high-power square wave (high power density) in the flash moment, and greatly improving the light output energy during the exposure period of the camera.By adjusting the flash length, the best combination of light emission and camera exposure time can be achieved, thus greatly reducing the impact on human eyes and minimizing the interference of ambient light on photography.The auxiliary camera system can meet the requirements of taking the clearest picture of the vehicle and driver under various light conditions.Its unique control technology, product performance and effect, installation convenience, service life and price are superior to ordinary flash lamps. It is the best alternative to the commonly used flash lamps for electronic police in the market at present, and also the preferred flash lamp for electronic police upgrading.
5、Studio flashHigh power flash lamps used in professional photography places such as photo studios, studios and studios are usually not portable due to weight, volume and other factors, and are often mounted on special tripods or slideways.
Flash Light is a kind of artificial light filling device. Its working principle is to store high-voltage electricity through a capacitor, and the flash tube is discharged by pulse triggering to complete instantaneous flash[1]。
Canon external flash
When the flash is fully chargedFlash synchronizationThe contact connects the flash circuit.During the flash light emission, light shines from the flash light onto the subject, and then reflects back from the subject to entercamera(for exposure) and flash metering element.The light measuring element quickly converts the light energy into an electrical signal input integral circuit, and then the integral circuit outputs an electrical signal proportional to the flash light quantity value;When the amount of flash light reaches the requirement of appropriate exposure, the output electrical signal of the integration circuit will cause the control circuit to trigger the flash stop circuit, so that the flash lamp will go out.
Because the continuous flash time of the flash lamp is very short, the flash metering element used must be a photosensitive element with fast response capability to adjust its light.
According to the different circuit structures, the control modes of automatic dimming flash lamps can be divided into parallel type and series type.
In main flashLamp tubeA relief pipe is connected in parallel at both ends of the.The ignition circuit of the main flash lamp is the same as that of the ordinary type.When the luminous amount of the main flash lamp reaches a certain reference value, it is received by the light measuring element, and the integrating circuit and the control circuit trigger the discharge tube to immediately discharge the energy that has not been discharged in the main control mode, so that the main flash tube is extinguished.
The circuit structure of the parallel automatic dimming flash lamp is simple, the price is low, and it is widely used.However, because it discharges all the remaining energy of the main capacitor every time, the recharging time is long and the battery consumption is large.
The series control mode is to integrate semiconductor switching elementsThyristor rectifierIt is connected in series with the main flash lamp. When the amount of light output by the main flash lamp tube meets the requirements for proper exposure, the thyristor rectifier automatically cuts off the discharge circuit, so that the main flash lamp tube is immediately extinguished, realizing automatic dimming control.
The advantage of the series control mode is that the remaining energy in the main capacitor is still stored, so the recharge time can be shortened, and the battery consumption can be reduced accordingly, which is conducive to rapid continuous flashing and recycling.The disadvantage is that the circuit is complex and the cost is high.
Function use
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There are also disadvantages when using the flash. For example, when shooting people, the flash light may remain in the pupil of the eye, which may lead to the situation of "red eye". Therefore, many camera vendors have added the function of "eliminating red eye" to the design. Before the flash is turned on, the weak light is used to adapt the pupil, and then the real flash is performed to avoid the occurrence of red eye.Middle and low-end digital cameras generally have three flash modes, namely automatic flash, red eye elimination and flash off.More advanced products also provide "forced flash", or even "slow flash" function.
Use of flash:
Flash is aFill lightThe device can ensure clear and bright pictures taken in dim conditions. When shooting outdoors, the flash can also be used as an auxiliary light source to emphasize the skin tone.Special effects can also be arranged according to the requirements of photographers.
Although there are no packaging and electronic standards in the flash LED field, manufacturers have defined many LED components for camera flash applications.When designing an LED flash in a camera phone, the criteria to consider are:
1. Optical characteristics;
2. Simplicity and flexibility of electronic design;
3. Pulse modulation function;
4. It can be effectively cascaded to obtain higher optical output;
5. Heat dissipation consideration;
6. Manufacturing and assembly considerations.In particular, the compatibility of LED modules with the manufacturing process used for camera phones[2]。
choose
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The key to choosing a flash lamp is to determine what type of flash lamp you need and how many functions it has. According to energy (brightness), flash lamps can be divided into three categories according to the voltage when the electrodes at both ends of the flash tube discharge instantaneously:
High voltage flash lamp with voltage above 2500 V
This kind of lamp has the advantages of large output energy and high brightness, which can meet the needs of large scenes and long-distance shooting. The disadvantages are large size, bulky and inconvenient to carry.Therefore, in addition to the special needs of professional photographers, amateur photographers should not choose.
500 Volt Flasher
The output power of this kind of lamp is moderate, which can meet the light demand for shooting under normal circumstances. It is convenient to carry, has a wide range of performance, and has a large number of models, so there is enough room for selection.It is one of the practical lamps for photographers and enthusiasts.
Low voltage small flash lamp below 500 V
This kind of lamp is small in size, light in weight, low in power consumption, cheap in price and wide in variety, which is suitable for professional and amateur photographers.
On site light filling
The main function of flash is to illuminate the scene when the light is insufficient to obtain the correct exposure image. Most digital cameras have the option of automatic flash. When the light is insufficient, the flash will automatically pop up and flash.
Increase shutter speed
Many times we use flash.It is not because the light is not enough for correct exposure, but to improve the shutter speed so as to achieve the purpose of solidification of dynamic images, such as shooting water droplets or moving portraits. If the exposure is conducted according to ordinary light measurement values, the images will be blurred and not clear enough, and flash lamps can solidify these images.
Increase depth of field
We know that the depth of field effect of an image is closely related to the aperture size. Generally, if the aperture is large, the depth of field is small;The smaller the aperture, the greater the depth of field.Using this principle, you can actually use flash to increase the depth of field.
Sometimes, due to the limitation of the on-site light, we have to use a large aperture to shoot, but the depth of field is not enough.We can narrow the aperture accordingly.Effectively increases depth of field.
Outstanding prospects
Many times we will find that in the shooting scene.The effect of the background is not ideal or simply not what we want.At this time, we can try to use flash to exclude the background, because when shooting with flash, the shutter speed is high, and the background outside the flash projection range will not be displayed due to insufficient exposure.The foreground is correctly exposed due to flash illumination, which can highlight the foreground and eliminate background interference.
Reduce contrast
Another common use of flash is backlighting.When shooting, it is very common for the scene to have too much light contrast (such as a portrait in backlight). Because CCD or film can display a limited range of brightness, in the scene with too much contrast, whether for light exposure or dark exposure, some image details will be lost.
In this case, the best way is to add light to the dark part to reduce the contrast of the picture. Of course, it is also possible to reduce light to the bright part.Flash is the most powerful weapon in this case!The specific method is very simple. Turn on the flash and let it illuminate the dark part when shooting. The effect is usually good.
Adjust color temperature
When shooting under the electric light, it is easy to show warm colors of yellow and red. Because the color temperature of the tungsten filament lamp is low, the flash lamp can effectively adjust the color temperature to restore the color of the subject correctly.
Flash lights can blind children. Is it true or not
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There was a widely circulated news on the Internet that after a 3-month-old baby was photographed by a mobile phone with the flash on, there was a burned round scar on the macular area of the right fundus, resulting in a right eye vision of only 0.2, while the left eye vision was still 1.2.Many people believe that the baby's eyes appear because of the flash light burnsVisual impairment[3]。
Not to mention whether the flash can blind the children's eyes, just look at the news, we can find many loopholes.The visual development of infants and young children is a gradual process. Usually, they can reach the visual level of normal people until they are about 6 years old. However, the distance from an object to be seen by a 3-month-old infant is about 3 meters, and the visual acuity is about 0.1.Therefore, the "left eye vision 1.2, right eye only 0.2" mentioned above does not conform to reality[3]。
So is flash really so harmful to children's eyes?Can it really lead to blindness in children?
In fact, flash has little effect on children's eyesight.First of all, the flash lamp is a hernia arc lamp, whose spectrum and light spot are equivalent to the ordinary light intensity in the daytime, and will not cause retinal burns.Secondly, flash light is a kind of instantaneous strong light. Its duration is very short and its speed is very fast. Therefore, the total amount of light entering the eyes is very small, and the possibility of blindness is also very small[3]。
Then, compared with mobile phones, the flash of professional cameras will be brighter. Will such flash lead to children's blindness?The answer is also no.The brightness of the light will decrease with the distance. When taking pictures for children in the studio, the distance between the flash and the baby's eyes is usually more than a few meters. With the help of devices such as a diffuser, the brightness of the light the baby's eyes feel is also safe[3]。
It should be noted that being exposed to too strong and continuous light will indeed cause damage to people's eyesight.The macular region of the human eye is a very powerful part of visual function and also a sensitive part. If the macular region is damaged, it will directly lead to serious damage to the main vision of the human eye.When adults are exposed to strong light, they will have a sense of self-protection, which will produce such stress reactions as blinking and narrowing the pupils, so as to avoid a large amount of light entering the eyes;However, the self-protection awareness of infants is weak, and their neural development is not perfect. When they are stimulated by strong light, their blinking and pupillary response to light are not as sensitive as adults. Therefore, children should pay attention to avoid continuous exposure to strong light[3]。
