27

The northern lights have been visible where I live recently, but I've found them to be practically impossible to see with the naked eye. Phone cameras, however, show them quite brilliantly. How is this difference explained?

Qmechanic
  • 220,844
Ryan_L
  • 1,319
  • 11
  • 14

3 Answers3

25

You have two vision systems. The daytime photopic system uses 3 types of color sensing cone receptors. This is why we see colors based on 3 primary colors. The nighttime scotopic system uses 1 type of much more sensitive rod receptor. At night, our vision is black and white. At intermediate light levels, it is possible for both systems to work.

A cell phone uses the same receptors at all light levels. Thus it can detect color at night better than we can.

mmesser314
  • 49,702
16

The cones, colour receptors, in the human eye are much less sensitive than the rods, black/white receptors so in reduced light the eye is not so good at detecting colours. Note how things look “grey” when it is dark.

Cameras do not have this problem and to compensate for the dark conditions, a camera can just take a longer exposure and collect light for longer, building up a picture of the scene and collecting colours that the rods in the eye cannot detect.
Also, after taking a picture one can enhance it by using photo manipulation app which can change the brightness/contrast/hue/saturation/etc to enhance a display.

Here are two images illustrate the difference.

enter image description here Camera

enter image description here Eye

I add a comment from @JackAidley:

It's worth noting that everything taken on a phone is extensively manipulated in software before you see it. Modern phones do not simply pass on the output of the sensor.

enter image description here This image has been changed by increasing the exposure using an app.

BeastOfCaerbannog
  • 107
Farcher
  • 104,498
0

With cameras you can adjust the shutter speed which is a measure of how long the camera will gather light before it constructs the final image. More light = more visible aurora. Besides, most camera images are digitally enhanced after they are taken in order to produce a more appealing image.

You cannot do that with your eyes.

mdkovachev
  • 547