Longlens

Longlens refers to a type of optical lens with a significantly longer focal length compared to standard lenses. This increased focal length has several key implications for photography and other optical applications. Primarily, long lenses magnify distant subjects, making them appear closer to the viewer. This magnification is often quantified by zoom ratios for zoom lenses, or simply by the focal length value for prime lenses.

The extended focal length also results in a narrower field of view. This means that long lenses capture a smaller portion of the scene in front of them, isolating the subject from its surroundings. This characteristic is highly useful for portrait photography, where it can help to minimize distracting backgrounds and create a pleasing bokeh effect, rendering out-of-focus areas as smooth blurs. Furthermore, long lenses can compress perspective, making objects at different distances appear closer together than they actually are.

In photography, lenses with focal lengths typically above 70mm are generally considered telephoto or long lenses. These are commonly used for capturing wildlife, sports, and other subjects where physical proximity is difficult or undesirable. In scientific instruments and optical systems, long lenses are employed where magnification of small or distant objects is required, such as in telescopes or certain types of microscopes. The design and manufacturing of long lenses often involve complex optical formulas to correct for aberrations and achieve sharp images.