数码摄影入门常识（Introduction to digital photography）1. What do you mean by F2.8-4/ or F3.5-F5/F7.6-F11 in the cameras parameter table?Answer: the F value of the camera lens aperture is not only a problem of aperture, but the actual amount of light is expressed. It is also related to the focal length of the lens. It is a relative value. For a general zoom lens, even though the apertures physical aperture is constant and the focal length becomes longer, the amount of light will be smaller and the aperture F will be smaller. F3.5-F5/F7.6-F11 said: the maximum aperture at the wide-angle end, the short focal length is F2.8, in the long end of the zoom, the longest focal length is F5; the minimum aperture at the wide-angle end, the short focal length is F7.6, in the long end of the zoom, the longest focal length is F11.Of course, the advanced professional lens has a constant aperture, that is, the F value does not change with the focal length. In fact, when the zoom is in, the physical diameter of the iris changes accordingly. A lens with a constant aperture is much more expensive than a lens of the same quality.2, why the digital cameras smallest aperture is not small enough, such as C-700 is F8, N995 is F10, and the traditional camera at any time F11, F16 or even F22 why?Answer: we usually say F2.8, F8, F16 aperture, aperture coefficient, relative aperture, aperture and aperture is not physical, physical aperture and lens aperture to the photosensitive device (film or CCD or CMOS) is related to the distance.When the aperture aperture is constant, the centre of a lens and a photosensitive device distance farther, the F number is small, on the contrary, the centre of a lens and a photosensitive device nearer, through the light hole to the optical density of photoreceptors is higher, the greater the number of F.Most non professional digital camera lenses have short focal length and very small physical aperture. When F8, the aperture of the aperture is very small, and the optical phenomena such as diffraction will continue to be reduced to influence imaging. Therefore, the general non professional digital camera minimum aperture in F8 to F11, and professional digital camera photosensitive device area is large, the lens from the photosensitive device far away, the aperture value can be very small.3, what is bracketing exposure? How to use?Answer: surround exposure (Bracketing) is an advanced feature of the camera. Although metering techniques are becoming more sophisticated, photometric deviations may still occur due to light conditions and subject changes. In order to prevent errors and missing important metering subjects, in many high-end traditional cameras have been introduced to the bracketing function, when you press the shutter, the camera is not a shot, but by the exposure of different combinations of continuous shooting more than one, so as to ensure always has a consistent with the photographers intention of exposure.In digital cameras, not only the introduction of exposure to the exposure of the exposure, and some cameras can even white dialogue, focusing, etc., surrounded by shooting.4, how to adjust exposure in auto exposure mode?Answer: Although the camera automatic metering technology is increasingly perfect, the central focus of metering, metering etc. partition are becoming more and more intelligent machines are machines, but still have time, uncertainty, if the subject brightness distribution is not uniform, such as in front of the bright background light portrait photos, is easily influenced by the background the brightness of the characters is underexposed, then use the AE lock or exposure compensation to solve this kind of problem, exposure compensation device of the camera can +2, +1, 0, -1 and -2, if the subject is underexposed, with compensation, increase exposure, and the use of negative compensation, reduce the exposure.5. What is shutter priority automatic exposure?Answer: shutter priority automatic exposure, also known as shutter automatic pre exposure, is one of the automatic exposure method. Suitable for shooting moving body or need long time exposure shooting situations, according to the intention to select the shutter speed, large moving objects need solidification, selected high shutter speed (such as 1/1000, F1/2000 or more), to shoot at night, flash synchronization, virtual moving body with slow shutter speed (such as 1/30 1, /2 or even longer, but dont forget to use a tripod and a remote control camera based on CCD, oh) (or film) sensitivity and scene brightness to adjust the aperture size, in order to reach the correct exposure.6. What is aperture priority automatic exposure?Answer: aperture priority automatic exposure, also known as automatic aperture first exposure, automatic exposure is one of the ways. Apply to the control of the depth of field shooting situations, according to the intention to select the apertur