Shooting method of long exposure photography

The "B-door" and "T-door" of the camera can be exposed for a long time, which can be used to get exposure for a few seconds, minutes or even hours. They are necessary shutter functions for celestial photography and fireworks night scene shooting. Digital cameras sold in the market only have B-door, but not T-door, while some small portable digital cameras do not have the functions of B-door and T-door.

The so-called light bulb, also known as manual shutter, means that when the shutter is pressed, the shutter opens to start exposure, and when the shutter is released, the shutter stops exposure. In other words, the exposure time of door B is determined by the length of the shutter pressing time, and it can be controlled freely without setting the exposure time. The name of door B is taken from the English word "bulb", which comes from the rubber ball squeezed out by the photographer when he opened the shutter in the old photo studio. This rubber ball shutter release device is still in use today and can still be seen on cameras in many modern photo studios.

The so-called T-gate means that when the shutter button is pressed, the shutter opens, exposure begins, and the shutter continues to open until the shutter closes when the button is pressed again. T-door and B-door have similar functions. Because the T door can keep the shutter open without pressing the shutter button all the time, it is more convenient to use than the B door.

Obviously, when shooting fireworks at night, you need to use door B or door T for a long time, so you need to fix the camera on a stable tripod. Because of the long exposure period, even a slight vibration of the camera will cause image blur. Even if you use a tripod, when you press the shutter button of the camera, it will inevitably produce vibration and affect the shooting. On the other hand, cable release can solve this problem. Just press the shutter button on the shutter line to control the camera shooting, which is very convenient. In addition, because cameras generally have no T-door function, it is necessary to hold down the shutter button all the time when using B-door for long-term exposure, which brings great inconvenience to photographers. The function similar to T-door can be realized by releasing the cable with cable release locking function. Just press the quick lock and you can let go. At this time, the camera will be exposed until you set a predetermined time, and then open the shutter door to complete a shooting. F 16-F22 is generally selected when running water and other scenes are exposed during the day, and F 16 is the main one. F22, because the aperture is too small, the lens is prone to diffraction, which reduces the picture definition and affects the image quality.

If you can't lower the shutter during the day, you can use CPL and medium gray mirror to reduce the brightness of the scene, so that the shutter can meet the time requirement of long exposure.

For long-term night exposure and starry sky exposure, the wide-angle lens is generally set between F5.6-F8 and F8, and the three lenses of SIGMA 10-20, NIKON 14-24 and CANON 16-35 can be set at F8. Generally speaking, the aperture priority mode of the camera can be directly used for long exposure during the day. First choose the aperture, and then the camera decides the shutter time. Exposure within 30 seconds does not need to enter M file. If the word LO appears in the camera, you need to switch to M exposure.

For long exposure at night, choose the M mode of the camera, first select the aperture, and then rotate the main dial wheel of the camera to adjust the shutter time. After more than 30 seconds, a light bulb will appear, and the camera's door B will be used for long exposure. Cable release must be used for the exposure of door B; It is unrealistic to hold down the shutter button of the camera by hand for a long time exposure, and the probability of jitter is too high, which is very easy to malfunction;

Long exposure at night, shutter time estimation, not clearly defined. Only by accumulating experience can we effectively grasp the shutter time according to the shooting environment. For the long exposure of the starry sky, if the focal length of the lens is known, the exposure time can be judged by the trajectory length of the stars. The shorter the focal length of the lens, the shorter the trajectory of the star in the same time, and the shorter the focal length, the longer the trajectory can be. The starry sky is exposed for a long time, and the night scene is exposed for a long time. Because the light at the scene is too dark to focus, change the AF of the camera to MF (manual focusing mode) and aim the initial stage of infinity at the focusing position of the camera.

When the camera is exposed for a long time during the day and can automatically identify the scene and focus automatically, the picture with the subject is focused on the subject, and the scene without obvious subject is focused on the first third of the scene; When there is a subject but it can't focus automatically, use a strong flashlight to illuminate the focus of the subject and then press the camera autofocus button; After focusing, remember to change the focusing mode to MF manual mode. For long exposure during the day, the generally set ISO is the default ISO for cameras, some cameras are ISO200, and some cameras are ISO100; ;

Long-time exposure at night is generally set to ISo200-ISo320, mainly because the longer the exposure time of digital cameras, the greater the noise, which is greatly influenced by external interference and the changing factors of field light, so long-time exposure will slightly improve ISO. 30 minutes after sunset is the golden density time, which is the best time for long exposure in the evening. The brightness of the sky is balanced by the gradual gray, the light is just on, the building is still illuminated by the faint skylight, and the color of the picture is very rich.

Half an hour before sunrise, the seaside in summer is about 5: 10-5:40. When there is a very weak red light in the sky, you should start exposure immediately. Until the sun rises on the horizon, you must find two prospects in different directions before exposure, which is enough to cope with the sunrise in different directions. The star orbit must be a place without stray light, and slight stray light will cause glare on the picture; Try to choose the leeward side of the mountain, and the requirements for facing the tripod in the wind are too high; Long-term exposure to urban scenery can choose commanding heights to avoid direct lighting; The supporting position of long exposure tripod must be stable and reliable, and it shall not be supported on soft mud, grass, hanging trees or overhead rocks. The end screws of tripod can be replaced by iron nails (titanium nails); After exposure for more than 30 seconds, the tripod should not be erected on the overpass or any place with vibration; The tripod can't lift the central axis. If the exposure exceeds 1 hour, you can put the camera bag on the ground and tie it with a rubber band and a tripod, but the camera bag cannot be hung.