White background

Learning goal

You will be able to explain why a white background comes out gray in a photo, starting from light falling off with distance. You will move the product away from the background and light the background separately with its own light, setting the product's light and the background's light independently of each other. You will measure in stops how much brighter the background must be than the product and confirm it with the histogram; you will open the background up enough to make it pure white, but not so much that it eats the product's edges. You will decide, as a preference, whether the product will look as if floating on the white ground, or standing on the ground with a soft shadow. If a hand holding the product is in the frame, you will mind how the background's brightness affects that hand's edges and tone.

The question

Your friend photographs the bowls on a white card for the marketplace. They have taped the card to the wall and curved it onto the table, put the soft light beside the bowl, and set the compensation to plus one stop. On the screen the bowl's cobalt blue is right, but the card behind isn't white; light gray near the bowl, a dirty gray darkening upward. A blurred smudge spreading from the bowl's base onto the table, too, as if gluing it to the card. The other products on the marketplace's page, though, sit in a pure white void, as if floating in the air. How does a product "float" on white?

Context

In the first product lesson you saw setting up a cornerless background curving from the wall onto the table, and that a white background fools the camera's metering and turns gray (Lesson 16.11). While learning the idea of a stop you calculated that when the distance from a small source doubles, light drops to a quarter, that is, by two stops (Lesson 8.8). While setting up portrait backgrounds you also used a separate light that lights only the background and doesn't fall on the subject (Lesson 20.8).

Setting the compensation to plus is sometimes enough for a small product, but it has a limit: every stop that opens the background opens the product by the same amount. A blue bowl or a dark leather wallet loses its own color before the background reaches white. In this lesson you will undo this tie by binding the background and the product to two separate lights.

Simple explanation

Why does a white background come out gray?

The light lighting the product falls on the background too, but the background is farther away than the product. Imagine the light striking the product from sixty centimeters, and the background from a hundred and twenty centimeters behind the product, that is, from a hundred and eighty centimeters away. Because the distance has tripled, the light reaching the background drops to a ninth; this is a difference of a little over three stops. When the product is correctly exposed, the white card falls to a gray close to the midtones. Its lower part, closer to the light, looks light, the far upper part dark.

Subject-to-background distance is the distance left between the product and the background, and in this lesson it does two separate jobs. While the product stands close to the background, the background gets a bigger share of the product's light, but the product's shadow also falls on the background. Moving the product a meter or two away from the background separates the shadow from the background and opens up room to light the background separately. On a background curving onto the table, the place where the product stands is still white card; that is why the distance between the product's base and the vertical part behind is what really matters.

How bright should the background be?

To light the background separately, one or two lights are turned to the background; the product's light looks only at the product. When the power of the two is set separately, the background can be opened up and down without the product's exposure changing. So that the background light doesn't leak onto the product, a flag or a piece of card is put in front of the light.

Background overexposure is how many stops above the product's correct exposure the background's brightness is. Less than a stop of overexposure leaves the background a light gray. An overexposure between one and one and a half stops often brings the background to pure white, that is, against the right edge of the histogram. This is the pure white some marketplaces ask for: the top value in all three color channels. In the histogram the peak formed by the background should touch the right edge, while the product's tones stay separate from it, in the middle. The camera's clipping warning should show the background blinking entirely, while the product doesn't blink at all.

Does the product float, or stand on the ground?

Edge wrap is the background's light, when the background is much brighter than the product's correct exposure, spilling over the product's edges and eating them, thinning them. As background overexposure goes past two stops, light coming back from the background into the lens leaks around the product. The bowl's rim melts into the white, a thin handle disappears, the whole frame's contrast drops. Keeping the overexposure around one and a half stops and fitting a hood to the lens limits this leak.

The product's floating, meanwhile, depends on its relationship with the ground. If the ground too goes up to pure white along with the background, the shadow under the product is erased and the product looks as if hanging in a void. Leaving a small, soft contact shadow right under the product ties it to the ground; a white, glossy acrylic sheet, on the other hand, forms a faint reflection under it. Which one to choose depends on the shop's language and the marketplace's rule. All can be right, as long as all the products have the same one.

If a hand is holding the product, the background's brightness wraps around the fingers' edges too. On light skin the outline of the fingers is lost in the white. Dark skin, on the other hand, comes out darker than it should in front of the bright background when the camera meters for the background. Taking the metering over the product and the hand, keeping the overexposure measured, and choosing a place for the hand a little farther from the background, protects the edges and the tone.

Visual evidence

Your friend pulls the table to the middle of the room and moves the curved card a meter and a half behind the bowl. They leave the bowl's light at the side and put a card flag in front of it; on either side of the card they place a small light each, and turn them to the background.

First they shoot with only the bowl's light: the bowl right, the background dark gray. Then they turn on the background lights, raise their power and stop when spot metering finds the background one and a half stops brighter than the bowl. In the histogram the background's peak is against the right edge. In the clipping warning the background blinks from end to end, the bowl doesn't blink at all. Out of curiosity they raise the background to three stops of overexposure. The bowl's rim has thinned in the white and the blue has faded; then they take the setting back.

Putting a small piece of card on the ground under the bowl, they cut the light a little; a soft, small contact shadow stays under the bowl. The craftswoman asks for another frame, holding the bowl in her hand. In the test where the background was three stops over, the edge of her fingers has blended into the white. At one and a half stops, though, the outline of the wheat-skinned hand is sharp, the paint-stained fingertips and the skin's warmth in place.

Common mistakes

Summary

A white background comes out gray because the product's light reaches it from farther away, and when the distance doubles the light drops to a quarter. Moving the product away from the background and raising the background with a separate light to one to one and a half stops above the product makes it pure white; when this overexposure is exceeded, edge wrap eats the edges of the product and of the hand in the frame. A soft contact shadow ties the product to the ground, while a shadowless ground makes it float.

Mini assignment

In this assignment you will light a white background separately and photograph a product at three different background brightnesses.

1. Set up a curved background with a white card, put the product at least a meter from the background and shoot a frame lighting only the product.
2. Light the background separately with a lamp or a flash and, without changing the product's exposure, shoot the background at one, one and a half and three stops of overexposure; in each frame look at the histogram and the clipping warning.
3. Photograph the hand of someone holding the product, with their permission, at one and a half and three stops of overexposure; look at the fingers' edges and the skin's tone.

Check yourself

• At which overexposure is the background pure white and the product's edges still sharp?
• In the histogram, do the background's peak and the product's tones stand separately?
• Are the outline and tone of the hand in the frame protected in front of the bright background?

Glossary

Mini quiz

1. Why does a white background shot with a single light lighting the product come out gray?

• A) Because the card is dirty
• B) Because the background, being farther from the product, gets less light
• C) Because the white balance is wrong
• D) Because the aperture is too open

2. What is done to protect the product's color while making the background pure white?

• A) The compensation is set to plus
• B) The product's light is raised
• C) The ISO is raised
• D) The product's exposure is kept fixed and only the background's light is raised

3. In what range is background overexposure usually kept?

• A) One to one and a half stops above the product
• B) At the same brightness as the product
• C) Four stops above the product
• D) One stop below the product

4. What does edge wrap lead to?

• A) The background turning gray
• B) The product's shadow darkening
• C) The edges of the product and of the hand in the frame melting into the white
• D) The colors saturating

Answers

1. B — When the distance triples the light drops to a ninth, and the background darkens by more than three stops.
2. D — A separate background light opens only the background without touching the product's exposure.
3. A — This overexposure brings the background against the histogram's right edge but doesn't eat the edges yet.
4. C — The light of a too-bright background spills over the edges, and thin parts and fingertips thin out.

Summary card

• Light falls off with distance; a distant background falls to gray.
• Move the product away from the background, light the background separately.
• Background overexposure: one to one and a half stops above the product; confirm with the histogram.
• Too much overexposure eats the edges; a hood and measured overexposure.
• A contact shadow grounds it, a shadowless ground floats it; the same for all.

Bridge to the next lesson

The background is now pure white, but to get it your friend used three lights, two stands and a huge curved card in the workshop. The craftswoman says she can't pack up and set up this arrangement again for every new bowl; there is only the end of a table and a tight budget. Is building a studio from cheap materials possible? The next lesson takes up building a small product studio that fits on a tabletop with a light tent, a few foam boards and a single light.