fixedfocus

Fixed focus (also seen as fixed-focus or fixedfocus) refers to a lens or camera system in which the focus is set at manufacture and is not adjustable by the user. In fixed-focus designs, the optics are arranged to provide acceptable sharpness over a broad range of distances, so subjects at typical working distances appear in focus without an autofocus mechanism or manual focus control. This approach is common in inexpensive cameras, disposable film cameras, many toy cameras, and some surveillance or portable devices where simplicity and reliability are prioritized.

In practice, fixed-focus lenses rely on a combination of a short focal length, small aperture, and optimized lens geometry to extend the depth of field. Because the focus cannot be changed, the user must position subjects within the intended distance range for acceptable sharpness. The trade-offs often include reduced performance for close-up or distant subjects and less control over perspective.

Applications include budget point-and-shoot devices, children's cameras, and certain entry-level surveillance cameras where a fixed scene distance is expected. They are also used in devices designed for quick response or rugged operation, where moving parts are undesirable.

Advantages of fixed focus include low cost, compact size, lack of moving parts, rapid focus acquisition, and high reliability in simple environments. Limitations include a narrow operating range outside which sharpness degrades, lack of control over focus for artistic or diagnostic needs, and potential image softness on high-resolution sensors when the fixed range does not align with the subject distance.