Capturing the Northern Lights

What Does The Aurora REALLY Look Like?

The Aurora is beautiful, but edited photos from professional cameras create an underlying expectation that the Aurora will appear to the naked eye with incredible brightness and saturation. In reality, the naked eye experience of the Aurora depends on many factors and is much more nuanced than most people think. In most cases, though, the Aurora will appear less saturated and bright to the eye than it will on a professional-grade camera; however, there are exceptions to this rule. To investigate further, we have to establish context to understand the differences between how our human eyes and our digital cameras capture light and process images.

Edited Camera Naked Eye

How We See

Camera VS Eye

How we perceive Aurora has a lot to do with how professional cameras and human eyes record light and create images.

In a camera, photons from the environment are directed into the camera through the lens and focused onto a digital sensor. These photons are collected in tiny wells called photosites creating small voltage signals which together form the analog image signal. This signal is transformed into 1's and 0's by the analog-to-digital converter, and the digital data are written to an SD card or other storage media.

Your eyes are similar to a camera: the cornea (lens' glass elements) focuses light through the pupil aperture onto the retina (sensor). However, the retina contains living cells instead of tiny, manufactured wells and electronics. When light hits the retina, photoreceptors convert light into electrical signals which then are used by the brain to reconstruct an image.

But while you can control the amount of light in your image (e.g., changing the shutter speed), your eyes and brain "see" involuntarily. Thus, cameras can be used to amplify weak light signals in the environment by utilizing long exposures and large-aperture lenses. Your eyes also can adapt to changing light conditions, but only up to a point.

What Does This Mean?

Cameras can essentially "see" more than we can. But what's important to realize is that the light is there; it is just too weak to see with our own human eyes. Many people look at photos of Aurora, the Milky Way, or deep space objects and immediately think they are photoshopped - fake.

There is nothing "fake" about a long exposure - you are simply using technology to see what is really there. In fact, our eyes are actually deceiving us; cameras can reveal the true beauty of the natural world.

Rods and Cones

Not only can we not control the exposure of our eyes, but our photoreceptors limit what we can see in the dark. At the back of our retinas are rods and cones, two kinds of photoreceptor cells. To put it simply, rods are very light-sensitive but don't resolve color or detail well. Cones, on the other hand, are what give light color. There are three types of cones - red, green, and blue, the primary colors of light. In dark environments, like under a star-filled night sky, our cones cannot perceive any color because of the weak light signal. Our rods, then, are the only photoreceptors that are activated, since they can still function in low light, but since they cannot see color, instead of seeing the natural color of the environment, we only see black and white. Cameras have a Bayer filter of RGB photosites and have no issue seeing colors in low-light environments. Not only can cameras "see" more photons than our eyes, they can also more accurately preserve color information in low-light environments.

How Does this Relate to Aurora?

First, we need to understand that Auroras can vary significantly in brightness. Rayleighs are typically used to measure the brightness of faint night sky objects. Night airglow at the zenith is typically around 30 R. Bright auroral arcs, however, are typically around 10,000 R, sometimes as bright as 100,000 R. The brightest Aurora has been reported around 1,000,000 R.

Camera settings can be configured to produce images with proper brightnesses regardless of the true brightness of the environment. E.g., the photos below have the same brightness but were taken with different exposure times. The Auroras were different brightnesses.

1.6 Seconds 8 Seconds

To the eye, the left Aurora would appear brighter since the camera needed less exposure time to produce an adequately-bright image.

Can We Ever See Color in Aurora?

Yes! A very faint Aurora will only trigger your rod photoreceptors, and although the true color of the Aurora may be green, you will only see black and white since rods cannot render color information. As an Aurora brightens, however, there will be a point when the light signal is strong enough to activate your cones, causing the true color of the Aurora to appear. This threshold most likely varies from person to person. Very bright Auroras will look colorful.

When people say "all Auroras look black and white," they either have not seen a very bright Aurora, or they may be color blind. While it's true that most of the time the Aurora does not appear to have color, during substorms when the Aurora becomes intense, many colors are visible. The comparison below illustrates this phenomenon. You can also see the difference in brightness in the Aurora by noting the shutter speeds used in each photo. The camera, lens, aperture setting, and ISO are the same in both photos to create a fair comparison.

10 Seconds 4 Seconds

Tricking Your Eyes to See More Color in the Aurora

Your eyes detect light from the entire visible environment, not just the Aurora, so you may be able to activate your cones by raising the ambient light around you. The moon and/or light pollution can provide enough ambient light to activate your cones without there being a bright Aurora.

While the increased ambient light may reduce the contrast of the Aurora with the surrounding sky, you will see more colors. Below are two comparisons of naked-eye Aurora visibility with and without a full moon in the sky. For quiet Aurora, even at low brightnesses, colors are slightly visible. For bright Auroras, the full moon creates vibrant colors.

Chasing Auroras among city lights or under light pollution may not yield the Best photos, but might actually aid in viewing since the increased ambient light will activate your cones, allowing you to see more colors.

While it will ruin your night vision, you can also look directly into a bright light source (e.g., car headlights or an LED flashlight) then immediately look at the Aurora. While the Aurora will appear very dim, you should see colors since your cones become stimulated for a few seconds by the bright light.

The Movement of the Aurora

What still photos don't convey is the movement of the Aurora, which is often extremely fast. Long exposures cause this movement to become blurry, failing to show the fine structures in the Aurora. This is where your eyes see "better" than the camera. Recent advances in camera technology have made real-time video capture of the Aurora possible.

Everyone Sees Colors Differently

Color is as much a physical quality as much as it is a personalized perception. Aurora emit photons with certain energies (wavelengths), but what a green-line emission looks like to one person might look different to someone else. Furthermore, since the colors in the Aurora still do not compare to the vibrant colors we see in the daytime, anyone with even very minor color blindness will struggle to ever see color in the Aurora.

Test Your Vision!

If you can make out the number in the image below, then you are likely not colorblind to faint green shades, the colors of the Aurora. If you cannot see the number, you may have some sort of green color blindness. Not being able to distinguish green from gray will make seeing colors in the Aurora difficult except during the brightest and most active displays.

Cameras vs. Eyes - The Main Takeaways

• The colors in the Aurora are real, you just can't see them because human eyes suck at seeing in low light compared to cameras.

• Human eyes and cameras work in entirely different ways which affect how they perceive light and create images.

• In low light situations, your eyes' rods take over, but rods can't see colors, so you won't see colors in the Aurora.

• If the Aurora is bright enough, some of your cones may activate, causing the colors to become more vibrant.

• In situations with more ambient light (e.g., full moon, light pollution), you may see Aurora colors more easily.

• Everyone interprets color differently: two people may see the same Aurora but only one may see colors.