Reproduction ratio in macro photography is a way of describing the actual size of the subject being photographed relative to the size of the image being projected onto the sensor; it does not refer to the size to which the image is subsequently enlarged or printed.
Let’s take an example (simplifying a bit): if a 30mm wide object takes up 10mm on the sensor, the reproduction ratio is 1:3, or about one-third life-size. Typically, this is what we can achieve with inexpensive extension tubes. If the projected image of that same object were 15mm wide, the reproduction ratio would be 1:2, or half life-size. And if the projected image were 30mm, i.e. the same width as the object being photographed, the reproduction ratio would be 1:1, or life-size. This can also be expressed as a magnification factor, with 1× being equivalent to 1:1, 0.5× to 1:2, etc.
The realm of true macro photography is that of ratios ranging from 1:1 to 1:10. Outside of these limits, we find ourselves in the realm of close-up photography or photomicrography.
Learn more:
- Difference between macro photography and close-up photography
- Extreme macro photography: the magic of microscope lenses
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