What is Hou Lian Flash Synchronization? What effect can it achieve?

What is Hou Lian Flash Synchronization? What effect can it achieve?

Generally, the shutter of 135 SLR camera has two shutter curtains, the front curtain (also called the first shutter curtain) and the front curtain (also called the second shutter curtain). The basic working procedure for pressing the shutter every time is: Press the shutter-> The curtain in front is open-> Photosensitive element (or film) is-> photosensitive; Hou Lian is closed.

At present, the shutter speed of ordinary digital SLR cameras is 30 ~ 1/4000 seconds, such as Nikon D80 and Canon 400D. And the highest shutter speed of quasi-professional cameras can reach /8000 seconds, such as Nikon D200, Canon 5D, etc., Minolta professional film camera? -9 even reached112000 seconds.

Differences and characteristics between Hou Lian synchronization and Hou Lian synchronization;

In order to explain the meaning of Hou Lian synchronization, we need to explain the difference between front screen synchronization and Hou Lian synchronization.

Front curtain synchronization: When the shutter is pressed and the front curtain is opened, the flash lights up.

Hou Lian synchronization: The flash lights up before the back curtain closes.

Front curtain synchronization is the most basic flashing mode. Because the flash flash time is short, the high-speed shutter is exposed by scanning the photosensitive element (or film) through the gap between the shutter blades, so it is only possible. Maximum flash synchronization speed? For example, the original flash synchronization time is 1/250 seconds, but we use the shutter of 1/500 seconds for flash photography. When the shutter gap fails to completely sweep the negative film, the flash ends, resulting in uneven illumination of the picture.

Hou Lian synchronization means opening the shutter for exposure and flashing before closing the shutter. So shooting a fast-moving object with bright spots will produce bright spots on the moving object? Behind you? The effect of drawing a trajectory.

In addition, there is a flash synchronization type? Slow synchronization is a kind of front curtain synchronization, which is named after the shutter is opened for a long time. Slow synchronization can realize normal exposure of foreground and background. The characters in the foreground are solidified by the high-speed flash from the flash, and the scenes with dark background are detailed by long-term exposure. If a camera without Hou Lian synchronization moves an object with bright spots quickly, it will produce a trajectory drawn by the bright spots to move the object? Front? This is because the effect of the flash is? Front curtain synchronization? Way.

There is no obvious difference between fast or high-speed flash synchronization and shooting relatively static subjects (buildings, stopped vehicles, mountains, the prospect of Yuan Ye or gardens, etc.). ). However, in slow or long exposure mode, or when shooting activities are relatively prone to moving and moving objects (people, moving vehicles, animals, sports and dance themes, etc.). ), using different flash synchronization modes will get completely different images, especially in low illumination environment. For example, in the evening or in low light, use a standard lens or a wide-angle lens to shoot the oncoming picture of an oblique cyclist. The camera is fixed on a tripod, keeping the shooting angle and picture unchanged. Use the shutter speed of 1/8 seconds or 1/4 seconds to set the Hou Lian flash synchronization mode, and you will get a picture with a tail behind the subject and a clear subject.

Working principle:

When the shutter is released, the flash does not emit light, so the subject is in an underexposed state (of course, if the illumination is too low, no image will be left on the film), but the photosensitive element (or film) can still record the underexposed image, and the subject is in a moving state, so the film records a smear.

When the time of 1/4 seconds or 1/8 comes, that is, just before the shutter closes, the flash lights up, and then the shutter closes. At this time, due to the light of the flash, the subject left a clear exposure image on the photosensitive element (or film), and then the shutter immediately closed, so the last point in this series of smears is the clear subject illuminated by the flash. It looks like a photo with a sense of movement and speed.

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