lisälinssi

Lisälinssi, often translated as "additional lens" or "supplementary lens" in English, refers to a lens that is added to a primary optical system to modify its characteristics. This is a broad term that can encompass various applications across different fields of optics.

In photography, a lisälinssi can be a teleconverter or a wide-angle converter. A teleconverter is placed between the camera body and the lens, increasing the focal length and thus the magnification. This allows photographers to achieve a longer zoom range without changing their primary lens. A wide-angle converter, on the other hand, attaches to the front of a lens, reducing its effective focal length and widening the field of view. This is useful for capturing more in a scene, such as landscapes or interiors.

In microscopy, lisälinssi can refer to auxiliary lenses used to alter magnification or correct for optical aberrations. For example, a Barlow lens is a type of lisälinssi that is placed in the eyepiece tube of a telescope or microscope to increase its magnification. Other types of supplementary lenses might be used to improve image quality or adapt the microscope for specific viewing techniques.

The term can also be applied in ophthalmology, where it might refer to an intraocular lens (IOL) implanted during cataract surgery. While the primary IOL corrects for distance vision, a supplementary lens might be added or a multifocal IOL used to provide vision at multiple distances, reducing the need for glasses. The specific function of a lisälinssi is always dependent on the context of the optical system it is part of.