Does the central part of my vision see in a different frame rate than the outer part?

Submitted by Calvinkelly t3_10suc0k in askscience

I just turned off my tv in a completely dark room and the LED on it seems to be off when I look directly at it. But when I look a little bit next to the LED so it’s not in the center of my vision anymore I can see it flickering like you see on cameras sometimes. Now I wondered why that could be and I figured that it must be a combination of my peripheral vision picking up light easier and my peripheral experiencing the same phenomenon that sometimes occurs with cameras.

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speculatrix t1_j75ni1f wrote

Yes, only the central part of your retina, called the fovea, has the best high quality vision for colour and resolution, that's part of the macula. This relies on light sensitive cells called cones.

The outer retina uses cells called rods which are more sensitive to light with a faster response time, and are better for night, but only offer monochrome vision. This is thought to be a survival trait, to see the movement of predators at night in your peripheral vision.

So, that full colour vision you have? Your brain is faking it.

https://www.kenhub.com/en/library/anatomy/photoreceptors

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_Oman t1_j77yd11 wrote

Your brain is faking all of it. The actual visual stimuli from your eye has far less bandwidth than you would think. Your brain builds a 3 dimensional internal representation of the world around you and is continuously updated part by part from your visual input. It's nothing like a computer monitor where all the pixels are being refreshed every single time.

In fact your ears will update the internal representation as well as your eyes. Your brain processes the sounds, directions, and timing of the sounds to help update your location within that representation.

Just how well your visual cortex understands the complex interaction of light on surfaces is truly amazing. There is a particular optical illusion that demonstrates how strong this knowledge of how light should work can influence what you believe is true.

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https://en.wikipedia.org/wiki/Checker_shadow_illusion

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Your brain INSISTS that A and B are different shades, because the rest of the checkerboard follows a consistent pattern, and part of it must be in shadow. It is one of those optical illusions that is nearly impossible to "turn off" because your visual cortex simply does this processing 100% of the time automatically.

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soMAJESTIC t1_j799klx wrote

I use this at night when trying to spot the cats in the yard. They’re practically invisible while directly in front of you, but you can see them almost clearly out of the corner of your eye.

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Jarlentium t1_j769f2w wrote

I would bet that this effect is less from the eyes themselves and more from the brain focusing on your center of view and only really watching for movement/changes in your peripheral vision

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The_Fredrik t1_j77mdt6 wrote

No, it’s a physiological difference in the structure of the eye.

The brain just fills in the gaps, just like it does with the blind spot.

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_Oman t1_j77yxe1 wrote

It's called your persistence of vision, or retinal persistence. It is not even across your visual field. It is also not the same for all individuals. Some people can detect a pulsing light source at higher frequencies than others.

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DatsunL6 t1_j77n4m3 wrote

There is a blind spot in the center of our vision where the optic nerve comes through to spread over the retina.

Another way to "see" the effect you notice is with the stars. When you look directly at a star it will disappear because it's over the blind spot on the retina.

Or, maybe the LED you noticed is large enough to surround this blind spot and something else is going on.

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Prestigious_Carpet29 t1_j78cegk wrote

Not quite true. The true blind-spot is a little off-axis from the centre of vision.

What you describe is the effect that dimmer stars may seem to "disappear" when you look straight at them because the centre of vision, the fovea (while having higher resolution and colour) is less light-sensitive.

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DatsunL6 t1_j78wgh4 wrote

That's right. Dimmer stars disappear when directly looked at and it's not to do with the blind spot.

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Ghitit t1_j7exhvd wrote

Any star I look at, bright or dim, disappears when I look at it because I have macular degeneration.

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