Equipment

Learning goal

You will be able to compare several ways of reaching true macro or a magnification close to it: a macro lens, hollow extension tubes that go between the body and the lens, close-up filters that screw onto the front of the lens, and a ring that lets you mount a lens reversed. You will estimate their magnification in advance with a short calculation, and know what each one sacrifices in terms of light, sharpness, focusing to infinity or working distance. You will choose which way will give the best result with the lenses you have, and plan your budget accordingly. When photographing a person's hands or a detail up close with these tools, you will get permission and render the texture of light or dark skin in its real tone.

The question

The day comes to return the borrowed macro lens, and looking at the price tag in the shop window, your friend accepts that they won't have one of their own for a while. On Thursday evening at the club everyone has a suggestion. One takes three hollow metal cylinders out of their bag: "Put these behind your old fifty millimeter and it becomes a macro." The one beside them shows a round lens they mounted by screwing it onto the mouth of their zoom. The one at the end of the table has turned their lens around and seated it on the camera. All of them promise to reach the same dragonfly eye. Is an expensive macro lens a must?

Context

At the opening of the track we set up together the one-to-one ratio, how many millimeters the frame covers and the measurement made with a ruler (Lesson K.1). When you first met macro lenses, you learned how close the subject can stand to the lens, the working distance (Lesson 12.9). In lens choice you also saw renting a lens before buying it and carefully examining a secondhand lens (Lesson 12.10).

A macro lens is a tool designed from the start to focus close, and it often gives the cleanest result. But it isn't the only way to reach macro. In macro, magnification depends on how far the lens stands from the sensor and how close it can get to the subject; every tool that changes these two things also changes the magnification. This lesson puts these tools side by side and calculates the price of each.

Simple explanation

What does an extension tube do?

An extension tube is a piece of tube placed between the body and the lens with no glass at all inside it. It moves the lens away from the sensor; this lets the lens focus much closer and magnify the subject. Its contribution to magnification is found roughly by dividing the tube's length by the lens's focal length: when a twenty-five-millimeter tube is fitted to a fifty-millimeter lens, roughly half a time, that is, a magnification of around 1:2, is added. The same tube on a hundred-millimeter lens adds only a quarter. That is why extension tubes are more effective on short focal length lenses.

Because there is no glass inside, an extension tube doesn't add a new lens flaw to the image. But it has a price: light. As the lens moves away from the sensor, the light falling on the sensor decreases; approaching 1:1, this loss is roughly two stops. Because the camera meters through the tube, it adjusts the exposure by itself, but the viewfinder darkens and the shutter speed gets longer. With the tube on, the lens can't focus far away, to infinity; it works only in a close range. Tubes that pass on the lens's electronic contacts keep autofocus and aperture control.

What does a close-up filter do?

A close-up filter is a magnifying glass that screws onto the front of the lens like a filter and lets it focus closer. Its power is written in diopters; with the lens focused at infinity, a one-diopter filter focuses at one meter away, a two-diopter filter at half a meter, a four-diopter filter at twenty-five centimeters. Its contribution to magnification, on the other hand, grows with the lens's focal length: on a hundred-millimeter lens a four-diopter filter gives roughly 0.4 times magnification, while on a fifty-millimeter lens the same filter gives half of that.

That is why close-up filters, the opposite of extension tubes, are more effective on long focal length lenses and at the long end of zooms. They don't lose light, are light and can be put on and taken off easily. Their price is sharpness: cheap single-element filters can soften the edges of the frame and cause color fringes; better filters made of two elements reduce these flaws. The filter's diameter needs to match the lens's filter diameter.

What does a reversing ring do?

A reversing ring is a ring that lets you turn a lens around and mount it with its front facing the body. A reversed short lens, for example a fifty-millimeter lens, can get very close to the subject and give a magnification of roughly around 1:1; shorter focal length lenses magnify even more when reversed. This is a very cheap way, but its price is high: because the lens's electronic connection is separated from the body, on many modern lenses the aperture and autofocus don't work, focus is found by moving the camera back and forth, and the lens's rear glass is left exposed.

Which way to choose depends on the lenses you have and what you want to photograph. For still subjects, extension tubes and reversing can give cheap and good results; for shy insects, a macro lens's long working distance is valuable; when walking around with a zoom, a close-up filter is the lightest solution. When photographing a person's hands, a ring or a piece of embroidery at this closeness, you need to get permission. On light skin sun spots and fine veins come forward, on dark skin the depth of the knuckle creases and glints; taking the metering from the skin itself keeps both in the right tone.

Visual evidence

Your friend fits a twenty-five-millimeter extension tube to their old fifty-millimeter lens and does the ruler test: seventy millimeters of the ruler enter the image; this means roughly 1:2. When they join two tubes, thirty-seven millimeters fit, almost 1:1; but the viewfinder darkens, the shutter speed gets two stops longer.

On the long end of their zoom, at a hundred millimeters, they fit a four-diopter, two-element close-up filter. About ninety millimeters fit on the ruler, roughly 0.4 times; the center is sharp, the corners a little soft. There is no light loss.

The same evening they want to photograph their mother's hands doing embroidery; their mother laughs and gives permission. On her light skin there are sun spots and fine veins, on her finger a needle and red silk. With the lens on the extension tube, they shoot from half a meter away in window light; they take the metering from the back of the hand, and the skin keeps its own pinkish color.

Common mistakes

Summary

An expensive macro lens isn't a must: hollow extension tubes give a large magnification on short focal length lenses by moving the lens away from the sensor, but sacrifice light and focusing to infinity; close-up filters work on long focal length lenses without losing light, but can give up some sharpness; a reversing ring is very cheap, but often loses aperture and focus control. Which one to choose depends on the lenses you have and the subject; a person's hands at this closeness are photographed in their own color, with permission and metered from the skin.

Mini assignment

In this assignment you will compare the ways of reaching macro with the lenses you have.

1. If you have an extension tube, a close-up filter or a reversing ring, or otherwise by borrowing from a club friend, try at least two ways.
2. Do the ruler test with each, note the magnification and the light loss, and compare the sharpness of the center and the corners of the frame.
3. With the way that gives the best result, photograph a detail; if you choose the hands of someone close to you, ask first, then take the metering from the skin itself.

Check yourself

• Which way magnified most, with which lens?
• Which way lost light, which one sharpness?
• Do the skin and texture of the hands look their own color?

Glossary

Mini quiz

1. When a twenty-five-millimeter extension tube is fitted to a fifty-millimeter lens, roughly how much magnification is added?

• A) A quarter
• B) Two times
• C) Half a time
• D) None

2. On which lenses is a close-up filter more effective?

• A) On long focal length lenses and at the long end of zooms
• B) Only on wide angles
• C) Only on phones
• D) On no lens

3. What is the most important price of an extension tube?

• A) Color fringes
• B) Light loss and not being able to focus to infinity
• C) The lens getting heavier
• D) The filter diameter changing

4. What is lost when many modern lenses are mounted reversed?

• A) Color
• B) Sharpness completely
• C) Magnification
• D) Aperture and autofocus control

Answers

1. C — Dividing the tube length by the focal length gives twenty-five over fifty, that is, half a time.
2. A — The filter's contribution to magnification grows together with focal length.
3. B — As the lens moves away from the sensor the light decreases and the ability to focus far away is lost.
4. D — The electronic connection of the reversed lens is separated from the body.

Summary card

• A macro lens is the cleanest way, but not the only way.
• Extension tube: big contribution on a short lens; light and infinity sacrificed.
• Close-up filter: effective on a long lens; no light loss, corner sharpness a risk.
• Reversing ring: cheap, but aperture and focus often go.
• Compare with a ruler; photograph hands with permission, metering from the skin.

Bridge to the next lesson

Having reached the dragonfly's eye with the lens on the extension tube, your friend is surprised when they enlarge the frame: the front surface of the eyes is sharp, but the back of the eyes, the rest of the head and the wings are completely blurred. Even though they stopped down to f/8, the sharp slice is no thicker than a millimeter or two. Why is almost everything blurry in macro? The next lesson takes up why the zone of sharpness in macro is measured in millimeters and how to manage it.