Macro photography magnification, working distance and focus stacking technique

1. Geometric definition of magnification (Reproduction Ratio)

A true "True Macro" must reach 1:1 (1.0x magnification).

• Geometric meaning of 1:1: The actual length of the object being photographed is 10 mm (such as a small ant), and the optical image refracted by the lens and projected on the surface of the full-frame sensor is exactly 10 mm in length!
• In comparison, the nominal "Macro" of many zoom lenses on the market is often only 0.2x or 0.3x, which is a close-up pseudo-macro.

2. The fatal physical dead end of macro photography: the contradiction between extremely small depth of field and small aperture diffraction

When the object is extremely close to the lens, the depth of field (DoF) shrinks dramatically to an astonishing 0.2 mm to 0.5 mm!

• Even if you shrink the aperture to f/8, you can only see half of the eye of a bee, and the antennae and wings behind it are all blurred into a blur;
• If you forcibly shrink the aperture to f/22 in order to pursue a large depth of field, the strong Airy disk diffraction will completely destroy the resolution of the entire photo and become detail-free.
• The only scientific way to break the deadlock: Focus Stacking!

3. A complete set of industrial practical assembly lines for depth-of-field synthesis

1. Equipment preparation: extremely heavy and stable tripod, ring-shaped double-head macro flash, precision two-way focus fine-adjustment slide (Macro Rail);
2. Aperture is set in the best image quality range: The lens aperture is firmly set at f/5.6 or f/8 (to ensure the peak optical resolution), the shutter speed is set to 1/160s according to the flash synchronization, and the ISO is set to 100;
3. Step-by-step micro-focus slice shooting:

• Manually rotate the lens to fine-tune the focus ring, and take the first shot in focus starting from the tip of the bee’s front antennae;
• Move the focus back very gently by 0.3 mm and take the second shot;
• Continuously shoot 20 to 50 pictures in sequence (many modern bodies such as OM System, Nikon Z8, Sony A7R5 support in-camera autofocus bracketing shooting, and each time the shutter is pressed, it automatically uses a micromotor to drive the lens to continuously slice and shoot 30 pictures);

4. Post-stage algorithm fusion synthesis: Import this set of sliced photos into Photoshop (select all layers → [Edit] → [Auto-align layers] → [Auto-mix layers (stacked images)]) or professional software Helicon Focus. The algorithm will automatically eliminate the blurred areas in each photo, extract only the sharpest pixels of each photo for seamless splicing, and finally output an extremely large macro masterpiece with 100% of every detail from the antennae, compound eyes to the tail pin.

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