Nikon Extension Tube M2 – 27.5mm (Not Meter Coupled)

The Extension Tube M2 from Nikon is a 27.5mm macro accessory designed to fit between a Nikon F-mount camera body and lens, increasing the lens-to-film distance to allow closer focusing and greater magnification for macro and close-up photography. As a non-meter-coupled extension tube, the M2 does not maintain automatic aperture indexing with the camera’s light meter, meaning exposure must be determined using stop-down metering or manual calculation rather than the open-aperture metering typical of coupled Nikon accessories.

This tube is part of Nikon’s classic extension tube lineup from the manual-focus era, which included various lengths designed to be used individually or stacked together to achieve different magnification ratios depending on the lens and subject distance required. The 27.5mm length of the M2 makes it well suited for close-up work with a range of Nikkor lenses, extending their minimum focusing distance well beyond what the lens alone can achieve, which is particularly useful for photographing small subjects like flowers, insects, and fine detail work where a dedicated macro lens may not be available or practical. Because it contains no optical elements, the extension tube introduces no additional glass into the light path, preserving the optical quality of the attached lens while simply shifting its focus range closer.

Since the M2 is not meter coupled, photographers using it on cameras that rely on automatic aperture indexing will need to switch to manual exposure and use stop-down metering, checking exposure at the taking aperture rather than wide open. This makes it best suited to photographers comfortable with manual metering workflows or those using it on fully manual camera bodies. Mount and dismount is via the standard Nikon F bayonet on both ends, allowing it to sit between camera and lens just like any other Nikon extension tube.

Specifications:
– Extension length: 27.5mm
– Mount: Nikon F-mount (bayonet, both ends)
– Metering: Not meter coupled (requires stop-down metering)
– Optical elements: None (extension tube only)
– Use case: Close-up and macro photography with compatible Nikkor lenses