Magnification ratio expresses the relationship between the physical size of a subject in the real world and the size of its projected image on the camera sensor. A 1:1 ratio (also written as 1x or “life size”) means a 10 mm insect appears as a 10 mm image on the sensor. A 1:2 ratio means the projected image is half the size of the subject; a 2:1 ratio means the projected image is twice the size, a regime often called supermacro.
True macro lenses are defined by their ability to reach at least 1:1 reproduction at minimum focus distance. Classic examples include the 100 mm and 105 mm macros from Canon, Nikon, Sony, and Sigma, the Olympus 60 mm, and specialty optics like the Laowa 100 mm 2:1 and the Canon MP-E 65 mm, which goes from 1:1 to 5:1. Zoom lenses with “macro” in their name typically peak around 1:3 or 1:4 and are arguably misnamed; the label often refers to close focus capability rather than true 1:1 reproduction.
Magnification has consequences beyond apparent size. Depth of field collapses dramatically at high reproduction ratios: at 1:1 with an aperture of f/8, depth of field on full frame is measured in fractions of a millimeter. Effective aperture also darkens with extension. As the lens racks out, light falloff means a marked f/2.8 may behave like f/5.6 at 1:1, costing two stops. Modern lenses correct the EXIF aperture for this; older lenses leave it to the photographer to compensate.
Working distance, the gap between the front of the lens and the subject, varies with focal length even at the same magnification. A 60 mm macro at 1:1 puts the front element only a few centimeters from the subject, useful for static work but awkward for skittish insects. A 180 mm or 200 mm macro provides much more working distance at the same magnification, which is why field macro photographers favor longer focal lengths. Crop sensor cameras add an additional advantage by capturing a smaller portion of the projected image, producing the framing of a higher magnification on full frame.
Several accessories increase magnification without a dedicated macro lens. Extension tubes shift the lens further from the sensor, raising the maximum ratio at the cost of infinity focus. Close-up diopters screw onto the front filter thread and act like reading glasses. Reversing rings mount a lens backward for extreme magnification. Teleconverters behind a macro lens multiply both focal length and magnification, useful for skittish subjects. Each method has tradeoffs in image quality, working distance, and convenience.
Because depth of field is so thin at macro distances, focus stacking has become the dominant technique for product, mineral, and insect photography. The camera shoots a series of frames with slightly different focus, often using a motorized rail or in-camera focus bracketing, then software merges them into a single deeply focused frame. Manual focus, a stable tripod, and careful technique remain the foundation regardless of which approach is used.