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Lighting

video art

For high-quality video shooting, you can use both conventional lighting lamps and special film lighting devices. This is due to the fact that modern video cameras have a fairly high sensitivity and even with automatic white balance provide accurate color reproduction in a wide range of color temperatures of the light source.

But still, preference should be given to quartz halogen lamps, which throughout the entire service life (at least 100 hours, high-quality lamps - up to 1000 hours) provide stability of the luminous flux and high light output (25-30 lm / W), their color temperature depends little on supply voltage fluctuations and is equal to 3200 °K.

The bulb of an ordinary incandescent lighting lamp, as a rule, loses its transparency over time, which at the end of its service life (up to 2000 hours) can lead to a decrease in the luminous flux by more than two times (the initial light output does not exceed 15-18 lm / W). The color temperature of such lamps is quite low and, with fluctuations in the supply voltage in the operating range, varies from 2200 to 2800 °K. This leads to the fact that the details of the image, painted in blue and blue colors, are poorly drawn. Therefore, it is better to supplement the usual lighting of residential premises with special lighting from a halogen lamp.

Fluorescent lamps are widely used for lighting public buildings, as they have a very high light output (30-50 lm/W). Their emission spectrum is discontinuous, but it is possible to conditionally determine the color temperature of LD lamps - 6500 °K, LCD - 6000 °K, LHB - 5000 °K, LB - 3600 °K, LTB - 2800 °K.

According to sanitary standards, the total illumination of industrial premises should not be lower than 80 lux, which is close to the optimal illumination for shooting (100 lux). As you can see, a report on the activities of colleagues at work can be done without additional lighting devices, however, in this case, the lighting will turn out to be low-contrast.

The required power of the lighting device depends on the area of the room, its design (absorbing properties of the ceiling, walls, furniture, floor), the light output of the lamp used and the design features of the lamp itself (its output coefficient, the degree of scattering of the light flux).

Direct directional light gives too high a contrast and tires the movie characters, so at home it is better to direct the light to the ceiling and to part of the wall. Let's evaluate whether the illumination of a room of 20 m2 from a lamp with a halogen lamp with a power of 500 W and a total of 50 percent return, aimed at a white ceiling, will be sufficient.

Suppose that the upper strip of the wall 0,5 m wide and 10 m in perimeter is additionally illuminated, these are quite real numbers. A half kilowatt halogen lamp gives a luminous flux equal to 500 W x 30 lm / W = 15 lm, and taking into account the minimum lamp efficiency of 000%, we get a minimum of 50 lm. The average illumination of the ceiling with an area of 7500 m20 and the upper part of the wall with an area of 2 m5 is 2 lm / (7500m20 + 2m5) = 2 lux. If at least a third of the light energy is reflected from the ceiling, then we will get the illumination of 300 lux necessary for video filming. In our case, 100 W would be enough, since 200/3 of the light flux is reflected from the white ceiling.

The lamp built into the camera helps to remove unnecessary shadows from the character's face that occur under overhead or backlight. The lamp can be replaced with a low-power (3-7 W) illuminator, which is easy to make on your own. If you choose a battery compatible with the camcorder for the light, then you will have a backup power source on the road. For lithium batteries with a nominal voltage of 7,2 V, 2 (or 3) series-connected krypton bulbs are needed, rated for a voltage of 3,6 V (or 2,4 V, respectively), giving a higher color temperature and having a higher efficiency, than ordinary flashlight bulbs. A reflector (or several) can be made from a half of a round rattle, glued inside with aluminum foil. The light must be focused, since a narrow beam that illuminates only the face is energetically more favorable.

Some SONY camcorders are equipped with a socket for attaching and connecting additional equipment, including illuminators powered by the camera and requiring increased battery capacity. To obtain the total capacity and output current, two batteries connected in parallel can be used, while the infoLITHIUM function must be supported only by the one that is directly connected to the camera.

In the car, 12-volt halogen lamps with a built-in reflector, powered by the cigarette lighter, will not be superfluous, and the voltage converter of the on-board network to power the camera and charge the batteries will not interfere. On the road, it is very useful to have several narrowly focused, low-power battery-powered illuminators on rods or tripods with clamps. It can be difficult to find a network extension cord in a strange house, and a 220-volt 200- or 500-watt halogen lamp with a clamp for mounting on a heating pipe is not found in every apartment.

Publication: video-lighting-notes.blogspot.com

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