What is macro?

Learning goal

You will be able to explain how close the word "macro" written on a lens or in a phone's settings really means getting. You will tell apart that a ratio such as 1:1, 1:2 or 2:1 says what size the subject forms on the sensor, and that this has nothing to do with what size the photo will be printed. By turning a ratio into how many millimeters of area the frame covers, you will calculate in advance which subject will fill the frame. You will understand that the same ratio gives different framings on full-frame and small-sensor cameras. You will measure with a ruler how close your own lens really gets. When photographing a person's fingertip or palm at this closeness, you will get their permission and show the texture of light and dark skin in its own color.

The question

Your friend is looking at a bright green dragonfly resting on a leaf in the garden. A fine net can be picked out on its wings, hundreds of small facets in its eyes. They bring their long lens in to its closest focusing distance; the dragonfly stays a small line in the middle of the frame. They turn on their phone's "macro" setting; this time it's a little larger, but still the net of the wings doesn't show. Someone at the club says, "a true macro lens shows it at its real size on the sensor, it says 1:1 on it." What does 1:1 magnification mean?

Context

In the special lenses lesson you met the macro lens designed to get very close to a small subject and form it large on the sensor, and the gap between the front glass and the subject (Lesson 12.9). In the sensor sizes lesson you saw that a sensor's side lengths change from camera to camera and how this narrows the framing (Lesson 3.3). You also know from the focal length lesson that from the same place, how large the subject looks in the frame grows with focal length (Lesson 12.1).

Macro is a door opening onto a scale the eye can't see in daily life: a dragonfly's eye, a leaf's veins, the reflection inside a drop of water. But the word "macro" is used very loosely; a phone's macro setting, the macro label on a zoom and a true macro lens don't give the same closeness. This track takes up entering this scale step by step; the first step is knowing how close you get with a number.

Simple explanation

What does 1:1 say?

Magnification ratio is the ratio of the image of the subject on the sensor to the subject's real size. 1:1 means that a one-centimeter insect also forms one centimeter long on the sensor. True macro is this ratio reaching 1:1 or more. 1:2 means the subject forms on the sensor at half its real size, 1:4 at a quarter of it. 2:1, on the other hand, says the subject forms on the sensor at twice its real size; this is a closeness that goes beyond macro and calls for special lenses.

This ratio has nothing to do with what size the photo will be printed. A dragonfly eye shot at 1:1 on a full-frame sensor appears roughly eight times its real size in a print thirty centimeters wide; the same frame on a phone screen may appear smaller than its real size. The ratio only tells what happens on the sensor. Many phones' macro setting and the macro label on many zooms actually give a closeness of around 1:4 or 1:3; calling these close-up is more accurate.

How much area does the frame cover?

Field width is the width of the real area the frame covers at a given magnification ratio. The calculation is simple: the sensor's width is divided by the magnification ratio. A full-frame sensor is roughly thirty-six millimeters wide; at 1:1 the frame shows an area thirty-six millimeters wide on the subject. At 1:2 this area grows to seventy-two millimeters, at 1:4 to one hundred and forty-four millimeters.

This calculation tells in advance which subject will fill the frame. A dragonfly roughly five centimeters long doesn't fit across the width of a full-frame frame at 1:1; at 1:2 it fits exactly. On a camera with a small sensor, for example a sensor roughly twenty-three millimeters wide, the same 1:1 ratio shows an area of only twenty-three millimeters: the frame is narrower, the subject looks larger in the frame. But the magnification ratio hasn't changed; because the sensor is smaller, the frame covers less area.

How do you measure your own lens?

The ruler test is measuring how much a lens really magnifies at its closest focusing distance by photographing a millimeter ruler. You put the ruler on a flat surface, set the lens to its closest focusing distance and bring the camera toward the ruler until focus is found. You read how many millimeters fit from the left edge of the frame to the right edge. If thirty-six millimeters fit on a full-frame camera, your lens is 1:1; if seventy-two millimeters fit, it is 1:2.

This test gives a more reliable answer than the label on the box; zoom lenses often magnify most at their longest focal length. This closeness can also be applied to people: the ridges of a fingertip, the lines of a palm, the curve of an eyelash. Permission matters more than ever for a part of the body magnified this much. On light skin fine veins and small spots come forward, on dark skin the depth of the lines and the small glints reflecting light; when the metering is made from the skin, both skins stay in their real tone.

Visual evidence

With the macro lens borrowed from the club, your friend first does the ruler test. On their full-frame camera, at the closest focusing distance, exactly thirty-six millimeters fit from the left of the frame to the right: 1:1. They try their own zoom; about one hundred and forty millimeters fit, so roughly 1:4. In their phone's macro setting, an area of roughly forty millimeters stays in the frame, but on the phone's small sensor this means a magnification far behind 1:1.

They go back to the garden. The dragonfly is still on the leaf. At 1:2 its whole body fills the frame; switching to 1:1, only its head and eyes fit into the frame. The hundreds of facets in its eyes, the fine net at the base of the wing can be picked out.

Their sister, whose skin is dark brown, opens her palm and shows a ladybird. Your friend asks permission; the lines of her palm and the insect's red shell are in the same frame. They take the metering from the skin; the depth of the lines and the warm brown skin are detailed.

Common mistakes

Summary

1:1 magnification means the subject forms on the sensor at its real size; true macro starts at this ratio, while 1:2 and 1:4 are from farther away, at the scale of close-up, and the ratio tells not the size of the print but only the sensor. Dividing the sensor width by the ratio gives the field width, and which subject will fill the frame is calculated in advance; a lens's real magnification is measured with a ruler, and the human body photographed at this closeness is shown in its own color, with permission and metered from the skin.

Mini assignment

In this assignment you will measure the real magnification of your camera and lenses.

1. Put a millimeter ruler on a flat surface and photograph the ruler from the closest focusing distance with every lens you have, including the phone's macro setting.
2. In each frame, read how many millimeters fit from edge to edge; divide the sensor width by this number to find the magnification ratio.
3. With the lens that magnifies most, photograph a small subject, a leaf, an insect or, with permission, someone's fingertip, and meter from the subject itself.

Check yourself

• Which of your lenses came closest to 1:1?
• Did the macro label on the box match the ratio you measured?
• Does the skin of the fingertip or palm look its own color?

Glossary

Mini quiz

1. What does 1:1 magnification mean?

• A) The photo being printed at its real size
• B) The subject forming on the sensor at its real size
• C) The lens focusing from one meter away
• D) The frame being square

2. On a full-frame sensor, roughly how many millimeters is the field width at 1:2?

• A) Thirty-six
• B) Eighteen
• C) Seventy-two
• D) One hundred and forty-four

3. At the same 1:1 ratio, why does the frame look narrower on a small-sensor camera?

• A) Because the sensor covers less area even though the magnification ratio hasn't changed
• B) Because the magnification ratio has increased
• C) Because the lens's focal length has grown
• D) Because the subject has shrunk

4. Which is the most reliable way to measure a lens's real magnification?

• A) Reading the label on the box
• B) Looking at the phone's macro setting
• C) Estimating the subject by eye
• D) Photographing a millimeter ruler from the closest focusing distance

Answers

1. B — The ratio only tells about the sensor; a one-centimeter subject is also one centimeter on the sensor.
2. C — The thirty-six-millimeter sensor width divided by the ratio that has dropped to half gives seventy-two.
3. A — The ratio stays the same, but the small sensor covers a smaller part of the subject and the frame narrows.
4. D — The millimeters that fit from edge to edge of the frame show the real magnification directly.

Summary card

• 1:1 = the subject at its real size on the sensor; true macro starts here.
• 1:2 and 1:4 are close-up; the ratio tells the sensor, not the print.
• Field width = sensor width ÷ ratio.
• A small sensor shows a narrower area at the same ratio.
• Measure with a ruler; photograph the magnified body with permission, metering from the skin.

Bridge to the next lesson

Your friend has to give back the macro lens borrowed from the club, and looking at its price, they hesitate. Someone at the club shows them hollow rings that go between the body and the lens, someone else a magnifying glass that screws onto the front of the lens. Is an expensive macro lens a must? The next lesson takes up the macro lens, extension tubes and close-up filters, how much each one magnifies and what it sacrifices.