Light in macro

Learning goal

You will be able to explain why light so often isn't enough in macro, and why a narrow effective aperture, a short shutter speed and a low ISO are all asked for at the same time. You will close this gap in daylight with a white card and a diffuser, and when needed with a small flash. You will know how a ring flash fitted to the end of the lens and a two-headed flash light the subject, the difference between the two, and why a diffuser fitted to the front of a flash softens the light. You will see that the quickly fading light of a flash sometimes leaves the background pitch black, and either use this as a choice or balance it with ambient light. You will know that when a hand or an eye is lit by flash up close, the camera's flash metering can darken light skin and pull dark skin toward gray, and set it according to the skin's real tone.

The question

Your friend waits for a windless morning, but this time the clouds come in. When they get close to the dragonfly on the reed with the extension tubes, the shutter speed the camera suggests drops to 1/15; when they raise the ISO, the frame turns grainy. They try to light the dragonfly's shadow side with a piece of card, but they are so close to the subject that their own arm and lens cast a shadow on the dragonfly. At the club someone shows them a round flash that fits onto the end of the lens. How do you light a small world?

Context

In the quality of light lesson you saw that how large the light source looks from the subject decides the edge of the shadow, and that diffusers enlarge the source and soften the light (Lesson 5.3). Talking about the problems of an on-camera flash, you learned that flash light falls off quickly as distance increases and how the camera chooses the flash power (Lesson 19.1). In the previous lesson you also calculated that in macro the effective aperture is narrower than the written one and that the aperture is kept at middle values for sharpness (Lesson K.3).

In macro, light is in the middle of a contradiction. The aperture is stopped down for the slice of sharpness and the effective aperture narrows even further; to freeze vibration and the subject's movement, the shutter speed must be short; for the detail to stay clean, the ISO must be kept low. All three ask for light at the same time. This lesson takes up how to gather this light with daylight, and when needed, how to use a small, close flash without spoiling the subject's form.

Simple explanation

How far does daylight go?

The soft light of a cloudy day is a productive start for macro, but it is often too little. On a sunny day, on the other hand, light is plentiful but harsh; it leaves sharp, dark shadows on a small insect. In both cases two small tools help. A white card or a small folding reflector sends light back to the subject's shadow side. A translucent diffuser held between the sun and the subject, on the other hand, turns harsh light into a large, soft source; because the subject is small, even a palm-sized diffuser is like a giant window to it.

In macro, closeness brings its own problem too: the lens, the hand and the arm can cut off the subject's light. A macro lens with a longer focal length works farther from the subject at the same magnification and reduces this shadow. When the light still isn't enough, flash steps in. The flash's very short burst freezes the small movements of both the subject and the camera; that is why it also works for a leaf swaying in the wind or a handheld camera.

Which flash, which light?

A ring flash is a flash fitted to the end of the lens that gives light from around the lens, in the shape of a ring. It lights the subject from the front, evenly and almost without shadows; it takes light into small, deep places, inside a flower or under an insect's head. Its price is form: without shadows the subject can look flat, and on shiny surfaces, in an insect's eye or a person's eye, a round, ring-shaped reflection of the light appears.

A twin macro flash is two small flash heads placed separately on either side of the lens, with adjustable angle and power. Setting one head stronger and the opposite one weaker gives the subject a direction and form; if both heads work at the same power, the light comes close to a ring flash. Whichever flash is used, a small diffuser fitted to its front, a piece of paper, a piece of foam or a ready-made box, enlarges the source, softens the edges of the shadows and reduces harsh reflections on shiny surfaces. A single on-camera flash, too, becomes a good light for macro when it is taken off the camera with a cable and held from the side.

Why did the background go dark?

The black background effect is a flash very close to the subject, its light fading quickly with distance, leaving everything behind in darkness and giving the frame a pitch-black background. In macro the flash is a few centimeters from the subject, while the background is a meter or two behind. By the time the light reaches there it is almost used up; with an aperture like f/11 and a short shutter speed, when the ambient light can't enter the frame either, the background becomes jet black. This is sometimes a wanted, dramatic effect, sometimes a misleading frame that looks like a night shot.

For a natural-looking background, lengthening the shutter speed or raising the ISO a little brings the ambient light back into the frame; the flash freezes the subject, the ambient light lights the background. Placing a leaf or a card close behind the subject also brings the background into the flash light. The camera's flash metering tries to pull the frame to an average gray: when you photograph a hand or a face close enough to fill the frame, light skin can come out darker than it is, and dark skin lighter than it is and gray. Raising the flash power a little on light skin and lowering it a little on dark skin returns the skin to its real tone.

Visual evidence

On the cloudy morning your friend first tries a white card: the dragonfly's shadow side opens up, but the shutter speed is still 1/30. They fit the ring flash borrowed from the club onto the end of the lens; at f/11, 1/200 and ISO 200 the dragonfly is sharp, the sway of the wind frozen. But there are round white rings in its eyes and the background is pitch black.

They fit a thin foam diffuser in front of the ring flash and lengthen the shutter speed to 1/60. The rings in the eyes soften, the green of the reed bed comes back behind as a faded color. The next day, taking a twin macro flash from the club instead of the ring flash and setting the left head stronger, the dragonfly's head gains form.

With the same twin macro flash they photograph their sister's dark-skinned hand, a snail in her palm. In the first frame her hand looks gray and faded; when they lower the flash power by a stop, her skin returns to its own warm brown, the rings on the snail's shell sharp.

Common mistakes

Summary

In macro, a narrow effective aperture, a short shutter speed and a low ISO ask for light at the same time; this gap is closed first with a reflector and a diffuser, and if needed with a small flash close to the subject. A ring flash gives an even, shadowless light from the front, a twin macro flash a directional light that gives form; a diffuser fitted in front softens both. The quickly fading light of a flash can darken the background, and the ambient light is brought back with the shutter speed; the tone of skin photographed up close with flash is returned to its real tone by raising the flash power on light skin and lowering it on dark skin.

Mini assignment

In this assignment you will compare three lights in macro.

1. Photograph a small subject, for example a flower, a pine cone or a snail, on a cloudy day first with daylight only, then opening its shadow side with a white card.
2. If you have a flash, shoot first bare, then with a paper or foam diffuser fitted in front of it; look at the color of the background and at the reflections on shiny surfaces.
3. Bring back the background by lengthening the shutter speed; if there is a hand or a face in the close-up, get permission and set the flash power according to the skin's real tone.

Check yourself

• Which light gave the subject the most form?
• Did the background go dark, and was this your choice?
• Is the skin photographed with flash in its own tone, or gray or dark?

Glossary

Mini quiz

1. Why is light so often not enough in macro?

• A) Because lenses are dark
• B) Because a narrow effective aperture, a short shutter speed and a low ISO ask for light at the same time
• C) Because insects don't like light
• D) Because macro is done only at night

2. What is the price of a ring flash?

• A) The subject can look flat and round reflections appear on shiny surfaces
• B) It changes the subject's color
• C) It is very heavy
• D) It doesn't deliver light at all

3. Why can the background be pitch black in macro shot with flash?

• A) Because the lens is dirty
• B) Because the sensor has heated up
• C) Flash light fades quickly with distance and at a short shutter speed the ambient light can't enter the frame
• D) Because the white balance is wrong

4. If dark skin filling the frame comes out gray when photographed with flash, what is done?

• A) The flash power is raised
• B) The flash power is lowered a little
• C) The ISO is raised
• D) The white balance is cooled

Answers

1. B — The three settings needed for sharpness, freezing and clean detail all reduce the light falling on the sensor.
2. A — Shadowless front light flattens form, and the ring-shaped source shows up on shiny surfaces.
3. C — The light of a flash a few centimeters away is used up before it reaches a background meters behind.
4. B — Flash metering tries to pull dark skin to an average gray; lowering the power brings back the real tone.

Summary card

• The light gap in macro: narrow aperture, short shutter speed, low ISO.
• First a white card and a diffuser; then a small flash.
• Ring flash even and shadowless; twin macro flash directional and shaping.
• Fit a diffuser to a bare flash; choose the black background knowingly or open it with the shutter speed.
• Flash metering pulls skin to gray: raise the power on light skin, lower it on dark skin.

Bridge to the next lesson

With the twin macro flash, the dragonfly's head now has form and is sharp. But toward noon every attempt goes to waste: the insects are restless, flying from one leaf to another, escaping the moment they get close. The birdwatcher at the club smiles: in the cool hour of the morning, on a leaf covered with dew, the same insects barely move. Why shoot early in the morning? The next lesson takes up insects, their sluggishness in the morning cool and approaching them without disturbing them.