Though often taken for granted, vision is one of the greatest miracles we have as humans.
Things like watching birds in the sky, viewing art in a museum, or watching your favorite TV are possible because of this big gift.
Here’s an interesting fact, though: While we truly appreciate the human vision, most of us know very little about it.
For instance, did you know that your eye can differentiate about 10 million colors?
We bet you didn’t.
In this post, I’ll answer a common question about the capability of the human eye: how many microns the human eye can see?
The Simple Answer
When you try to search for the smallest size your eye can see, you will likely come across sources stating that it can see objects of about 100 microns or 0.1 millimeters.
Others will tell you it comes down to the diameter of one strand of hair.
This article states that the smallest size that the naked eye can recognize is in the range of 0.058-0.072 mm (or 58-72 microns).
This is a little different than the aforementioned source above.
That’s because there are specific factors that affect vision.
I’ve tackled that below…
Human Vision Is A Little Complicated
The human range of vision can be described as “infinite”.
The smallest object your eye can see depends on the object in question.
Ideally, the eye can see objects of all sizes if they scatter or emit sufficient light to trigger detector cells.
For instance, if you place a light-emitting object at a distance of 15 cm from your face, it will appear to be of the same size which is 1.75 nanometers in width.
To put it into context, this is roughly about 10 times larger than the width of one gold atom.
Another great example is fog and smoke. Both typically have minute atoms that the naked eye wouldn’t normally be able to see.
Smoke which is made of water vapor and soot scatters visible light thus obstructing the view. When infrared light passes through its particles, it comes into view.
This is to say that the human range of vision can perceive things at any distance as long as there are no obstructions.
Also, they have to be bright enough. This is why we can see galaxies and stars that are hundreds (or even thousands) or light-years away.
The Issue Of Resolution
Like camera lenses, the human eye also has a resolution of its own.
This can be simply referred to as the closeness of two objects before they merge and blur into one.
The eye’s resolution allows color vision, light perception, and depth perception.
When an image is formed directly at the retina, the eye will see it as a clear object.
Depending on the size and object of the object, the eye’s lens will assume a specific shape that in turn, changes its focal length.
When you focus on an object, it is possible to change the ciliary muscles of your eye’s lens by squeezing or relaxing them.
That can affect how your eye sees objects of different sizes.
Visual Acuity Also Plays A Part
While there’s a standard for the microns the human eye can see, visual acuity is also a factor in your vision.
This is a fancy word for clarity of vision. It essentially denotes a person’s ability to see small details with precision.
Acuity is dependent on neural and optical factors. The former refers to the health of the retina, brain pathways, and the way the brain interprets images while the latter is all about the sharpness of an object on the retina.
Visual acuity is measured at a 20-foot distance.
People that recognize small objects at a distance are said to have a visual acuity of 20/20.
In other words, they can see clearly objects that are normally seen 20 feet away.
Those with a 20/100 vision must be 20 feet close to see what a person with a 20/20 vision can see normally at 100 feet.
Besides acuity, other factors such as eye coordination, peripheral awareness (side vision), color vision and focusing ability, and depth perception also contribute to one’s visual ability.
Wrap Up
The human eye can see any object size provided it emits enough light to activate its detector signals.
One person can see an object as small as 70 microns while another person’s vision can only go up to 100 microns.
Other factors such as eye resolution and visual acuity also matter.
