Macro and Close-Up Photography Quiz: Masterclass Lesson 6

True macro means a magnification ratio of 1:1 or greater, where the subject appears on the sensor at its real size or larger. A 1 cm insect covers 1 cm of the sensor. A ratio of 1:2 is half life size, which is close up work but not true macro.

Extension tubes are hollow spacers that fit between the camera and the lens. Moving the lens farther from the sensor lets it focus closer, which raises magnification. Because they contain no glass, they add no optical flaws, although they do cost some light.

At macro distances depth of field becomes extremely thin, often around a millimeter or less at 1:1 even at f/8. Only a sliver of the subject can be sharp. Photographers deal with it by stopping down, aligning the sensor with the subject, or focus stacking.

Focus stacking means shooting several frames, each focused at a slightly different distance, and blending the sharpest parts of each in software. The final image shows more depth of field than any single frame could. It is common in macro and landscape work.

At macro magnification even a slight breeze moves a flower or insect far out of the very thin plane of focus and blurs it. Photographers shoot early in still air, use windbreaks or clamps, or wait for gaps in the wind. That is why wind is called the macro photographer's main enemy.

When light passes through a very small opening it spreads out, which is called diffraction. At f/22 and smaller this spreading softens fine detail across the whole image. In macro it often cancels much of the benefit of the extra depth of field.

Macro work needs more depth of field than wide apertures give, because the zone of focus is so thin at close range. Around f/8 to f/16 gives more depth while keeping diffraction softening limited. At f/22 and beyond, diffraction starts to cost noticeable sharpness.

A ring light circles the front of the lens, so light hits the subject from all around the lens axis. Shadows fall behind the subject and are almost invisible, giving even, flat illumination. That suits recording fine detail, dental work and specimens, but not dramatic shaped light.

At the same magnification, a longer macro lens focuses from farther away. A 200mm macro gives much more working distance than a 50mm, so insects are less likely to flee and there is room for light. Both can reach 1:1, so the longer lens does not give more magnification.

Insects are cold-blooded and rely on ambient temperature to power their muscles. In cool early morning conditions their body temperature is too low for fast movement, so they remain perched and accessible much longer than they would be once the day warms.