Focal length (Focal length) is basically a central point from the lens to the film plane (other photographic materials) on the clear distance between images.
Focal length of the unit is usually used mm (millimeter) to indicate that a lens is generally marked in front of the lens, such as 50mm (this is commonly referred to as "standard lens", means for 35), 28-70mm (our most popular lens), 70-210mm (telephoto lens). Aperture (Aperture) is used to control the camera light on the size of the device. A large aperture, the amount of light entering the camera will be doubled, reduce the amount of light when the aperture will be halved, aperture size using the F values to indicate that the sequence is as follows: 1, f/f/1.4, f/2, f/f/4, 2.8, f/f/8, 5.6, f/11, f/16, f/22 and f/32, 44, f/f/64 (the smaller the f value, Aperture larger) shutter (Shutter) is used to control the exposure duration of the device. Shutter in General can be divided into microscopic point plane between the shutter and the shutter curtain (that is, people often mentioned sheet steel shutter). Shutter speed shutter opening time. It is a light film of time sweep (exposure time). For example, "1/30" means the exposure time of 1/30 second, equally, "1/60" means the exposure time of 1/60 sec, 1/60-second shutter speed is 1/30 sec shutter speed. Rest and so on. Depth (Depth of field) when an object aggregation clear, from the object in front of a distance to the back of a distance are quite clear. The focus is quite clear that the distance from front to back is called depth of field. About depth of field of some description: the smaller the aperture, the greater the depth of field. The larger the aperture, the smaller the depth of field. For any aperture, its focus is the focus of the depth of field is approximately 2 times the front depth of field. The shorter the focal length of the lens, the greater the depth of field; the longer the focal length of the lens, the smaller the depth of field. Depth of field preview (Depth of field preview) because in the view through the viewfinder, in order to be able to on the brightest possible image composition and aggregation, the lens will always be open to the maximum aperture, so that the maximum aperture is always render the most shallow depth of field. In order to get to see the actual depth of field, the camera offers the depth of field Preview button, press the button, the aperture to the selected size, see the scenes and after shooting the film (memory card) to record scenes. Speed represents the speed of the PC of photographic materials. Speed units of "degrees" or "fixed", as "ISO100/21" represents the speed to 100 ° c/21 of film. The higher the speed, the more sensitive film (in the same shooting environment normal shooting the same picture needs less light, its performance is to use higher shutter or smaller aperture). 200 degrees of sensitivity of the film emulsion is 100 ° film twice, 400 degrees of film sensitivity is 200 ° film 2 times, rest and so on. Color temperature varying light contains different pigment called "color temperature". The color temperature of the unit for the "K" (Kelvin). We usually use daylight color negatives can adapt the color temperature to 5400K-5600K; lighting-type A, type b can adapt the color temperature 3200K 3400K and respectively. Therefore, we should, according to the subject, environment to select different types of film, or a partial color phenomenon (unless used filter corrects color temperature). Report: color temperature is defined as a "hypothetical, so that it is in black metal minus 273 ° c (absolute zero) environment, as the temperature, the black metal emits different wavelengths of light, the light that metal temperature plus 273 is such a light color temperature". For example, the metal is heated to 25 ° c, the metal has issued a red light, the red light of color temperature is "2500 + 273 K, meaning" the red light of color temperature is 2773K. Lower color temperature, long wavelength of light (red, Orange, light), the higher the percentage content; the higher the colour temperature, the shorter wavelengths of light (light blue, violet), the higher the percentage content. For example: noon daylight color temperature is about the color temperature 5500K; Flash is about 5600K; blue sky color temperature of about 100 Watts normal 20000K; bulb light color temperature is approximately 2600K. White balance due to different light conditions of different spectral characteristics, shoot photos often partial color, for example, in fluorescent blue is partial, the incandescent lamp is yellowish, etc. In order to eliminate or mitigate such color cast, digital cameras and camcorders under different light conditions to adjust color settings for the photo color distortion as possible, make the color restore correctly. Because this regulation often white, therefore calls the white balance.
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