Macro Magnification Calculator

Reference table

Maximum magnification for M43 lenses with ≥0.25× native capability, with extension tube projections. Extension tube values use the formula M_new = M_native + tube / focal and are approximations. Accuracy decreases for very short focal lengths.

What magnification means

Magnification ratio describes how large the subject appears on the sensor relative to its actual size. At 1:1 (1× magnification), a 17.3mm object fills the full width of an M43 sensor. At 0.5× (1:2), a 34.6mm object fills the same width. At 2× (2:1), a 8.65mm object fills the frame.

True macro is defined as 1:1 or greater. Most standard lenses reach 0.1–0.3×, which is useful for close-up shots but not macro work. Dedicated macro lenses are designed to reach 1:1 while maintaining good sharpness throughout their focus range.

Extension tubes

Extension tubes fit between the camera body and lens, physically moving the lens further from the sensor. This allows the lens to focus closer, increasing magnification. They contain no optics, so image quality is not degraded, but you lose the ability to focus at infinity.

The magnification gain from an extension tube is tube length ÷ focal length. A 10mm tube on a 60mm lens adds 10/60 = 0.17×, turning a 1:1 macro lens into a 1.17:1 lens. The same 10mm tube on a 100mm lens adds only 0.1×, so shorter focal lengths benefit more per mm of extension.

Common M43 extension tube sets: Kenko DG (10mm + 16mm, stackable to 26mm). The Olympus EX-25 adds 25mm. All preserve electronic contacts for AF and stabilisation.

M43 sensor and field of view

The M43 sensor measures 17.3 × 13mm. Field of view at any magnification is simply sensor size ÷ magnification. At 1:1, you can frame a subject 17.3mm wide. At 2:1, only 8.65mm wide. Knowing the field of view tells you whether a subject (a coin, an insect, a flower stamen) will actually fit in the frame at that magnification.