Human eyes resolution

[donpedro]

I was just bired during my drive home and I was thinking...

What would be human eyes specification if it would be digital camera or camcorder ?

Frequency, angel, minimal distance focus, resolution, aperture and so on....

[tgpo]

http://clarkvision.com/imagedetail/eye-resolution.html

[donpedro]

Thanks for the post, but I couldn't find any of those "computer or electronics numbers".

[Faustus]

I kinda assumed that since the eye is analog is has no specific rez.

[g_shocker182]

Taking a wild guess here...wouldn't it be infinite/ perfect?

[Conquest10]

but what about people that use glasses?

[g_shocker182]

Because they lack focusing capabilites?

[donpedro]

There must be some numbers..... some examples...

1. When you look at bicycle wheel.... there is some speed in which spikes make illusion that it rotates oposit direction = frequency

2. Try look at the watch very up close.... there is distance where you can't focus anymore = macro focus minimum distance

3. If you make a lot of very small dots in (let's say) square it will look like solid color = resolution

Maybe nobody realy tried to covert those thinks into PC world measurements but they exist. I think.

[vitualis]

Umm... "resolution" doesn't really make sense in terms of the eye.

Basically, if you are taking about so many pixels high, versus so many pixels across, firstly you have to decide how big the pixels are...

A more useful figure would be the smallest angle subtended that can be distinguished by the eye (i.e., how small something is / or how small the difference is and you still being able to tell the difference).

If you are talking about the maximum data density we can pump into someone's eye (in terms of "pixels"), then one way would be to count the number of photoreceptors in the retina. However, this is highly misleading as:
(i) there are a lot less optic nerve axons running to the brain than there are photoreceptors
(ii) visual processoring of information starts at the retina
(iii) psychological filters
(iv) so many other reasons...

Regards.

[donpedro]

Well.... I guess I was too bored It just appeared to me while driving through the night that I could see airplane landing and flying low over highway that this might be interesting picture but than I realized that there is no lense that would capture it clearly and I thought "what would be aperture of my eye that I can see it clearly.

[Solarjetman]

Well, if you're bored and thinking about eyesight, ponder this one.

Describe what the color red looks like without using examples, for instance if you had to describe it to a blind person.

I think that color, along with other things like optical illusions such as the bike wheel, do not have so much to do with how sensitive our eyes are, but how our minds process that data. After all, color is nothing more than a photon wave at a given frequency. The "color" is added by our brains to distinguish between the frequencies. Other animals can see a little into the infrared range, where humans cannot. so what "color" do they see?

[thayne]

Resolution refers to pixles, a digital image. We don't see in pixles so there is no resolution. We see in analog (waves), not digital (pixles).

[vitualis]

Resolution refers to pixles, a digital image. We don't see in pixles so there is no resolution. We see in analog (waves), not digital (pixles).

Well, that's not really true. We don't see in "waves".

It's just that there is no real useful value. Which of the following would you take?

• number of photoreceptors
• number of optic nerve axons
• number of neurons mapping the visual field in the visual cortex
• etc...

Regards.

[vitualis]

Frequency, angel, minimal distance focus, resolution, aperture and so on....

I was thinking actually...

Frequency (updates per second) -- well the human perceptual system usually can't tell the difference much beyond around 24 fps. As for the physiological "speed" of the "eye" itself, I don't think that there is a comparable number -- as you could consider each axon in the optic nerve as kind of like an analogue wire ... with the frequency of pulses down the axon being related to the intensity of the signal (e.g., "brightness").

"Angle" -- I assume that you are talking about "focal distance". If that is the case, then human vision is around equivalent to a 50mm lens for 35mm film cameras (hence a 50mm lens being called a "normal" lens). This is fixed (we are not blessed with the facility of "zoom" eyes though that would be kind of cool).

"Minimum focal point" -- it depends on your age. When you are young, you have a nice spring lens and you have a quite strong power of accomodation -- probably less than 10 cm. By the time you are old -- it increases past 50 cm. Any book on physiology will have better numbers.

"Resolution" -- as before argument. Since I don't have my textbooks with me, I can't give you numbers (e.g., photoreceptors, axons in optic nerve), but I presume a Google search should give results.

"Apeture" -- I don't know how to compare to a 35mm film camera system, but you pupil can constrict to probably around 1mm (pinpoint) and dilate probably up to around 10 mm (again, I don't have my textbooks with me -- try Google).

There is also something of sensitivity. Unlike digital cameras which basically have a fixed "ISO" level (that can be boosted with amplifiers but with noise), your eyes have remarkable dynamic range. Think about it. You can walk around in very bright sunlight and see well and at the same time, you can walk around in near dark (e.g., candlelight) and see reasonably okay (with enough time). This is as your eyes will actually up and downregulate the amount photoreceptive material in your rods and cones (though it takes time) -- which can change their sensitivity to light by several orders of magnitude -- amazing!

Regards.

[i_am_dave]

Finally, an intelligent thread in the Off-topic forum!

Frequency is a little misleading. Studies have shown that the human eye moves constantly. Scientists have paralyzed the muscles in eyes and have noted that vision then goes to white.
So, that being the case, photoreceptors measure delta's in intensity. They are not cumulative like a CCD, therefore the concept of frames per second breaks down.
I wonder what the numbers are for how much of a change a photo-receptor are?
Also, if you will notice when looking at the bicycle wheel directly, it is a blur. But move your eyes quickly across it, and you will get one or two images of the spokes frozen.

[vitualis]

Also, if you will notice when looking at the bicycle wheel directly, it is a blur. But move your eyes quickly across it, and you will get one or two images of the spokes frozen.

That's the function of the extrinsic muscles of the eyes and a number of reflexes. These muscles are the fastest in the body. They in part work autonomously -- if the moving object isn't too fast, then you will actually be able to track it with your eyes (they e.g., will follow the item from left to right and then very quickly flick back to the left and continue tracking --> giving the illusion that you can actually continuously clearly see the fast moving object).

These reflexes are actually quite amazing. Notice how if you hold a camcorder (without image stabilization) and you film while walking that the image jumps about everywhere. Ever thought about why you don't get the same effect with your vision when you walk or run?? The muscles surrounding your eye quickly and effectly compensate -- now, if we can only get image stabilizers for camcorders as good as OUR organic system!

Regards.

[BJ_M]

also take into account that the brain "fills in" missing data in moving or glancing vision .. therefore only in static fields you could make some sort of tests ..

also the human visual system is logarithmic and not linear - therefore your ability to "see" is dependent on wavelenth..

human vision is not as good as some other animals ... like birds, who can see more colors than humans .. even within our limited bandpass .. or some birds (hawks) who can see mice or shrews at 1 mile ...

if fact human vision isnt all that hot (or smell or taste or touch or electrical simulation (if we were sharks or other creatures)) .. well we can make up for it in other things i guess ...

[BJ_M]

i found another good web site on this subject

http://www.mic-d.com/curriculum/lightandcolor/humanvision.html

[henk schuifkaas]

[i_am_dave]

In the color blindness test, I cannot see anything in the inner 4 circles. I can see numbers in the outer 4.
What does that mean?

[BJ_M]

it means you are not colour blind (depending WHAT numbers you see that is)

[Solarjetman]

What does that mean?

It means you have normal vision.

[vitualis]

In the color blindness test, I cannot see anything in the inner 4 circles. I can see numbers in the outer 4.
What does that mean?

I wouldn't think it meant anything... on your PC monitor. The tonal variations on those tests are VERY SLIGHT and I can't see anything either (but I definitely can on the real (physical) test images. BTW, if you don't have those particular forms of colour blindness, you should be able to see a number.

In the "microanatomy" of the retina picture, the pigmented cells at the back are basically a black screen to prevent "reflections". The cones and the rods are the photorecepters. Notice how you have the horizontal and amacrine cells between the photorecepters and the ganglion cells (the axons of which go to form the optic nerve -- basically the cable that takes the visual info to the brain). These cells basically already do some visual processing!! As I stated before, the processing of visual information starts at the level of the retina.

Rather than just passive photoreceptors like on a digital camera, the retinal already contains circuitry that's built in for detecting specific things such as edges, and motion. As I seem to keep saying, amazing!

Regards.

[BJ_M]

this is a better more complete test for color blindness

http://www.toledo-bend.com/colorblind/Ishihara.html

or here http://members.aol.com/protanope/colorblindtest.html

[Solarjetman]

BTW, if you don't have those particular forms of colour blindness, you should be able to see a number.

This may not be true. There are some test that if you do see a number you have that disorder, and if you don't, then your vision is normal. The number is there, but its not a different color. Something else is different about the dots and a person with a disorder will pick up that difference as another color.

[energy80s]

Well for what its worth, I am red / green colourblind. From the above examples (which I agree probably don't give an accurate rendition of colour anyway) I can only make out the number 6 on the top left and top right circles (can't see anything in the middle two) and can only see the number 74 in the bottom right circle.

[vitualis]

Yes, but I don't think those pictures are that type of test...

Actually, looking carefully, I think that picture is showing the following...

LEFT most image = the real image
The next three images are what YOU WOULD SEE if you HAD that particular type of colour blindness...

Regards.

[vitualis]

Well for what its worth, I am red / green colourblind. From the above examples (which I agree probably don't give an accurate rendition of colour anyway) I can only make out the number 6 on the top left and top right circles (can't see anything in the middle two) and can only see the number 74 in the bottom right circle.

You just proved my hypothesis!

The left top and bottom images are the "test" images.

The right three are to show us "normal" people what people with colour blindness would see...

Regards.

[Solarjetman]

Actually, looking carefully, I think that picture is showing the following...

I think you are right. I looked up tritanope vision, and it is the inability to see the difference between blue and yellow. As there is no blue or yellow in the normal version, they should be able to see the number. The other two are a form of green/red blindness and they would not be able to notice the difference.

Not to sound conceited, but I know I am seeing it properly. I took a color blindness test just a little over a year ago and it was given by a doctor. They said I had no problems. I see numbers in the outer 4, but nothing in the inner 4.

[i_am_dave]

this is a better more complete test for color blindness...

Cool, I knew I wasn't color blind, just a little paranoid!