What Constant Aperture Lens?
We know , for Digital SLR Camera Lens , aperture is a measure of quality is an important indicator. Great goal better than the small aperture of the lens opening higher grade . In addition , we often hear a theory called lens constant aperture lens and this type is also considered a symbol of high quality lens . So what is the purpose of the constant aperture ?
The lens itself constant , the average maximum aperture telephoto end and the wide- angle maximum aperture of the lens, and does not mean that can not change the aperture of the lens. We all know the general zoom lens , aperture wide-angle end and telephoto maximum aperture is not the same . For example , Canon EF- S 18 -55mm F3.5- 5.6 USM , its wide end ( 18mm side) of the maximum aperture is F3.5, but the end of telephoto ( 55mm side) into a maximum aperture of F5 .6 the . However, wide-angle to telephoto actually need more than a grand opening, telephoto wide angle required for a faster shutter speed , so that , in general , the telephoto end of the film will be more limited .
Obviously, this type lens has no such problems in the telephoto end can be maintained with a large wide-angle end of the opening of the same, so that the adaptation shooting range has increased . At the same time , all targets large aperture are large aperture lens ( F2.8 constant in the majority , there is a small constant F4.0 ) , the image quality is very good, and mechanical properties as have a good performance , therefore, a constant aperture lens naturally became a symbol of high quality lens .
We can think of this type lens image quality is not in itself bring many benefits , but constant aperture is a feature of the high quality lens and is the most important features . Therefore , we usually use constant aperture lens to represent a class of quality. But inevitably , a constant aperture lens can not be small, light, who is forced to compromise .
Now , I would recommend some " constant aperture " target you .
This constant aperture lens are very good, so I advise you .
