nærfokusfilter

Nærfokusfilter, also known as a close-up filter or diopter, is an accessory used with cameras to allow for closer focusing distances than the lens would normally permit. It essentially acts like a magnifying glass placed in front of the camera lens. These filters come in various strengths, indicated by a diopter number (e.g., +1, +2, +4), with higher numbers allowing for even closer focusing.

Using a nærfokusfilter does not change the aperture or shutter speed of the camera. Instead, it reduces the minimum focusing distance of the lens. This is particularly useful for macro photography or for capturing small details of objects without needing a dedicated macro lens. The effect is to bring the subject closer to the camera, making it appear larger in the frame.

When using a nærfokusfilter, it's important to consider that image quality might degrade, especially with stronger filters or at the edges of the frame. Aberrations such as chromatic aberration and softness can become more pronounced. The effective aperture of the lens also changes due to the magnification, meaning the depth of field will be shallower than it would be at the same focal length without the filter. Nærfokusfiltre are typically screwed onto the front of the lens and are available in standard filter thread sizes.