Original subtitles

Hi. I'm William Lidwell, and this

is Universal Principals of Design.

In this movie: Top-Down Lighting Bias;

putting your design in the best possible light.

From the time of its dedication in 1922,

the lighting of the Lincoln statue

at the Lincoln Memorial was of particular

concern to its designer, Daniel Chester French.

The original lighting cast Lincoln's face

in a ghostly fashion.

Electric lighting was installed in the late 1920's

which showed Lincoln as French intended, day and night.

French followed up with photos to the commission

responsible for the memorial,

showing exactly how the statue should be lit:

from the top left, giving the impression

of lowered thoughtful brows;

and how it should not be lit: from the bottom.

What you're seeing here are two identical

3-D models of the Lincoln statue;

one lit from the top, and one lit from the bottom.

These images have not been altered in any other way.

The difference in perceived facial expression is dramatic.

Unfortunately for French, his instructions

were not always followed ,,,

especially during events at the Memorial.

For example, many reported that Lincoln

looked downright shocked and surprised

during Obama's address at his first pre-inaugural concert.

The statue looked that way because

the flood lights pointed up at the podium,

and they overwhelmed the top-down

lights in the memorial.

The shadows were lost.

The same incorrect lighting was used

during a George Bush, Sr. pre-inaugural ceremony

and a Martin-Luther King address.

No doubt, poor Daniel French was turning in his grave.

So, what's the top-down lighting bias?

The bias is a tendency to interpret objects

as being lit from a single light source from above.

It's found across all age ranges and cultures,

and likely results from humans evolving in an

environment lit from above by the sun.

As a result of the bias, dark or shaded areas

are commonly interpreted as being

farthest from the light source,

and light areas are interpreted as being closest.

Objects that are lighter at the top

and darker at the bottom are interpreted

to be convex, or sticking up,

and objects that are darker at the top

and lighter at the bottom are interpreted

to be concave, or sunken in.

This image taken by the lunar reconnaissance orbiter

appears to be either a Martian crater,

or a Martain plateau, depending on its orientation.

These images are the same,

except that the one on the right

is turned upside-down.

In design, when objects leverage

the top-down lighting effect,

two-dimensional things can be made to look

three-dimensional through shading.

For example, when light on the top

and dark on the bottom,

buttons are perceived to be raised.

When dark on the top and light on the bottom, depressed.

In each case, the apparent height and depth

increase as the contrast between light

and dark areas increases.

Interestingly, objects look most natural

when lit from the top-left,

rather than from directly above.

This bias drives a common technique

of artists and graphic designers.

For example, in a survey of over 200 paintings

taken from the Louvre, the Prado,

and the Norton Simon Museums,

more than 75% were lit from the top left.

When things are lit from the bottom,

they not only tend to look unnatural,

they can look scary.

This is what happened with Zombie Lincoln,

and it's the basis of the classic practice

of children lighting their faces from below

with a flashlight when telling scary stories.

It can make building architecture look

foreboding and dangerous as well.

So, how can designers leverage

the top-down lighting bias?

As standard practice, use a single,

top-left light source to make things look

natural and inviting, including

figures in artwork,

exhibits and displays,

rooms and buildings,

and user-interface controls.

Adjust the difference between light and dark areas

to vary the perception of depth.

And in situations where you're trying to create

unnatural-looking or foreboding things or environments,

maybe you're making a haunted house

or designing a film set,

and you want to create a spooky atmosphere,

bottom-up lighting is the way to go.

So, whether you use your knowledge

of the top-down lighting bias to create

more intuitive interface buttons and controls,

to make objects and environments appear

more inviting or more foreboding,

or to ensure that a sculpture that took you

seven years to design and build

is not made to look like a zombie,

remember, always put your designs

in the best possible light.