Shot in the end how to choose, what choice according to this problem could be a problem faced by many digital SLR users. When the user selects the lens is somewhat easy reference, Japanese photographer Racecourse Nobuyuki think, based primarily on four main areas to choose the focal length, maximum aperture, close-up capability and describe force when buying lenses. The following four aspects of this particular presentation.

         A focal length

The focal distance of the focal length is short. For example, when you put a magnifying glass facing the sun, the other face of the paper, move up and down to a certain distance, the paper will be clustered into a very bright spot, but will get through the charred pieces of paper into small hole, so called "focus." Closest focusing distance of the lens refers to the closest distance shot at very close to the subject's state of the lens can focus. From the lens center to the paper distance is the focal distance of the lens. The camera, the focal length of the lens is equivalent to the "center" of the camera tube or solid state imaging device image plane distance.

The longer the lens focal length, the narrower the horizontal viewing angle of the lens; the shorter the lens focal length, the wider horizontal viewing angle of the lens

The shorter the focal length, angle and field of view will be. So short focal length lens is also known as a wide-angle lens

Scene being shot in front of a clear range called the prospect of deep, clear range called back after the depth of field. Prospects for deep depth of field and post together, that is the entire television screen from the nearest point to the depth of the farthest clear clear point, called panorama deep. General said deep depth of field refers to the panorama.

          Select Lens first to note is the focal length of the lens, the focal length is actually viewing angle, focal length different perspectives are different. In addition the user must be clear, what is the main purpose of my purchase of the lens is? Is to shoot landscapes or shoot people, and so on. As we all know, shoot the scenery is appropriate wide-angle lens, while the figure is appropriate to shoot telephoto lens, so we must first decide what you want to buy the lens focal length according to photographic purposes.

            Best focal length is shooting landscapes angle focal lengths 24mm, telephoto focal length 200mm (35mm are standard specifications, the same below). When the standard zoom 28mm wide-angle focal lengths from 24mm rear perspective evolved to become larger, can greatly broaden the scope of accommodating the scene. Generally shooting landscapes lens maximum aperture requirements are not too high. If you mainly shoot landscapes, then, when you select the zoom lens is 24mm wide-angle focal lengths basic suffice. As telephoto focal lengths, at least have a 200mm, 300mm or if 400mm telephoto focal length is more ideal, the DOF will be greatly enhanced. Traditional multi-focal length telephoto zoom lens is 300mm, used in digital SLR is 450mm, expanded 1.5 times the focal length, using them makes one feel more happy, this is precisely the value of digital SLR lies. Now produced in digital special ultra-wide angle lens wide-angle focal lengths generally to 12mm, equivalent to 35mm sizes 18mm, 28mm compared to 35mm focal length specifications expanded nearly 1.5 times, so that the landscape around the scene of the shooting range greatly widened.

         Shooting people is the best focal length 85mm. To 35mm size standards, basic shooting people to choose the lens focal length to 85mm as standard. 85mm focal length portrait shot was close to the screen effect medium format camera shot, not only a sense of the appropriate distance, but people's faces look very natural, the distance between the camera and the subject's basic character can be maintained in the normal talking distance. 85mm focal length can be very prominent figures blur the background. To get a good blur, should choose a large maximum aperture of the lens. 85mm focal length on a digital SLR is about 135mm, although the screen shot seems a little perspective is a little weak, but basically no serious problem, so the focal length of the lens shooting people at least to about 85mm.

       Flowers have to shoot for a traditional SLR 100mm macro lens will suffice. 100mm macro lens can wait times Photography, can flower looks great, however, and other times when photography or near photographic magnification, due to the depth of the focal length of the long view, prone to jitter, so the image stabilization measures should be considered when shooting. From this point of view, 50mm macro lens on a digital SLR with easier to use.

Second, the maximum aperture

          The true value of the maximum aperture of performance under low light conditions to improve the amount of light to achieve the best combination of exposure. Shooting landscapes generally do not require the ability to blur the lens, in addition, unless otherwise dark place outside lens diameter is generally not too demanding. However, when the 70-200mm zoom 2x teleconverter leaving the installation becomes 400mm telephoto focal lengths and the autofocus with AF, the best choice is the maximum aperture F2.8 lens. Large aperture conducive accurate focusing in dark conditions. Shooting with a large aperture lens character even in low light where the handset can also take advantage of natural light shooting. In addition, a large maximum aperture of the lens can bring a faster shutter speed, so sports photography also requires large-aperture lens.

          Another reason for the large aperture lens is able to freely blur the background, but also to ensure blur quality. F1.4 maximum aperture of the lens when the aperture down to F2, regardless of the image quality or the quality of bokeh background are stronger than the maximum aperture of the lens and F2. Therefore, large-aperture lens aperture narrow a file has considerable value, should make good use of any photographer's camera this feature.

Third, close-up ability

         Close-up lens focal length capacity is second only to another maximum aperture of selective focus. This is both for the wide-angle lens, standard lens or telephoto lens are the same. So, close-up capability in the end how much it would be suitable?

First, let me shoot landscapes with wide-angle lens, wide angle lens for close-up capability is almost nothing, but when shooting with a wide view of the landscape as the background of flowers, often put flowers looks bigger, wide-angle lens close-up capability under similar circumstances it is very important.

50mm standard lens close-up of existing capacity are about 45cm, basically meet. However, large-diameter standard lens photography when using the shortest distance, since the lens is extended, often there is a big aberration, causing poor quality, this point must be mentally prepared to purchase and use.

    Note Closest focusing distance is short does not mean that the maximum magnification large

     The maximum magnification represents the maximum size of the image sensor imaging of the subject. It is the closest focusing distance is closely related to, the use of the closest focusing distance is the maximum magnification shooting. But if it is a zoom lens, then the maximum magnification is also concerned with the focal length, when the zoom lens at the telephoto end to reach its maximum magnification. In addition, short focal length lens, even if the closest focusing distance is shorter, its maximum magnification telephoto lenses have less time. So, if you want to get a larger magnification, the lens must have a close-up capability and a longer focal length.

       Telephoto lens for shooting landscapes if so, for close-up does not have much capacity requirements. However, if used for shooting people or flowers, close-up shot capability is very important.

Fourth, the expression

       When you select the lens many people first note is how this lens image sharpness. Photos of use determines what kind of sharpness of the lens. High quality lens primarily for professional photographers use, if only in general photography, there is no need to spend a lot of money to buy high-priced high-quality lenses. In addition, the lens aperture size image sharpness and also has a direct relationship, when a narrow maximum aperture of the lens from the image sharpness after a two tranches will be greatly improved.

         Distortion is an optical phenomenon caused by the optical performance of the lens, each lens distortion is impossible does not exist, manufacturers in the production of lens aberrations are corrected, and strive to distortion control at minimum. Generally speaking there are three main lens distortion: the wide-angle end of the zoom lens barrel is prone to distortion at the telephoto end is prone to distortion and pincushion distortion hats type of wide-angle end after correcting barrel distortion generated. On the current status of the lens, the most prominent problem is the wide-angle end of the barrel distortion, buy a small barrel distortion to choose styles as possible.

Bokeh photography on beyond the capabilities of the human eye, so aroused great interest. Blur itself a quality problem, there clean and dirty difference. Too beautiful for bokeh, image looks soft; blur too dirty, the light will be dispersed to the four corners of the screen, but is not part of the imaginary circle was pretty serious is the formation of a double imaginary state. Ideal lens, the light will evenly dispersed to form a very natural blur state.

        Ability of the lens to blur the background and lens aperture also has a relationship. A lot of shots from the maximum aperture down a two steps immediately after the picture becomes sharper, but the ability to blur the relative decrease. Ideal lens with a maximum aperture to shoot images are very sharp and blur effect is also very good.

           Backlit photography due to the strong sunlight or other strong light is repeatedly reflected in the mirror will form a halo and flares on the screen. This small part of the light to form a halo and flares will not only not on the screen imaging, but also reduces the quality of chaos reflection in the mirror is formed. To prevent this, you must use the hood backlit photography. Excellent lens to take a thorough process to prevent halos and flares in the manufacturing process, even when shooting in backlit contrast is also good.