SLR camera lens knowledge, what to pay attention to!

1, 18-200mm and other numerical values are the legendary focal length. Just like the focal length of the eye or a magnifying glass, a camera lens is similar to a magnifying glass, and these values are his focal length. 30- 100 of the wide-angle end below 30mm belongs to the calibration area, and above 100 belongs to the telephoto area, which has been introduced upstairs. Different focal lengths should be used according to different shooting requirements. 2. The aperture of SLR is adjustable. You can turn the aperture with the lens and see that the circle in the middle will become bigger and smaller. This is the aperture. In fact, digital cameras can adjust the aperture, but some card machines can automatically adjust the aperture, not manually. 3. There is no standard for the choice of entry-level lens. If so, it is estimated that it should be considered from the aspects of price, function, imaging quality and brand. Beginners should not buy anything too expensive. Moreover, I don't buy many lenses with different focal lengths at the beginning, and I can't use them after buying them, so I recommend several models: 65438. 2. Tenglong (Chinese name Longteng) 17-50mm f/2.8 has good focal length, excellent imaging, large aperture, easy to carry, and can be used for landscapes and portraits. Every evaluation is more quality than Canon L head, and a better focal length can be your usual head. It is the vice factory that will encounter problems such as out of focus (that is, inaccurate focus and blurred shooting); 3. If the telephoto lens is a Canon EF-S 55-250/4-5.6 IS lens (Canon is an anti-shake telephoto lens), this is just a choice that you have no money but want to take a long view. If you have money, it is not recommended. It is recommended to buy Canon EF 70-200/2.8L IS USM (legendary white) or Canon Guo Xuwei with the same focal length and no image stabilization. These two models are the best. But the aperture is very important. The larger the aperture, the more expensive the lens. You should do your best. The aperture size is not as big as you think. For example, Canon EF 70-200/2.8L is USM, and its maximum aperture is written as 2.8, which is actually 1/2.8, that is, the reciprocal, so the smaller the value, the larger the aperture, and it is a multiple of the root number 2. For example, if you have a funnel, the size of the funnel mouth is the size of the aperture. Now you have to pour the paint into the bucket and use a big funnel, which will be faster, but it will splash in all directions (that is, the main body of the big aperture is clear and the background is blurred); With a small funnel, although it will not splash, it is slow (that is, the subject and background of small aperture imaging are very clear). Zoom range means that the focal length of this camera is 18-200mm. Refers to the range of zoom lens from wide angle to narrow angle (short focal length to long focal length). Refers to the span between the maximum and minimum focal lengths of a zoom lens. The larger the focal length range, the more convenient it is to use, but the lens with high requirements for lens quality and low quality has a large focal length range and poor imaging. This lens is also known as the mirror of walking the world and a good helper for traveling. Also, the larger the focal length, the more suitable for shooting the distant view.