Lens cap
A lens cover is placed on a lens to protect the lenses from dirt and damage . In the early days of photography , the lens cap also served as a camera shutter that controlled the exposure of the film material.
In the case of interchangeable lenses , a distinction is made between the front cover and the rear cover. The front cover protects the front lens, which is exposed on a ready-to-use camera. The back cover attaches to the camera port on the lens while it is not attached to the camera.
Nowadays, front covers are mostly made of plastic and snap into the filter thread of the lens with a spring mechanism , so that they are easy to put on and remove. The required size of the cover results from the filter thread diameter of the lens. Simpler plastic models adhere to the outer diameter of the lens thanks to their precise fit. In the case of higher-quality versions made of metal that can be clipped on , accuracy of fit and a sufficiently firm fit are achieved by a velvet insert in the inner edge of the lid. There are also lens caps that can be screwed into the filter thread.
The type of rear cover depends on the lens connection of the respective camera system, which can be designed as a screw thread or a bayonet connection. The back covers of different camera systems are therefore usually not compatible with one another.
