Bio-pixels

"Don" wrote in message

Does anybody happen to know the actual resolution of the human eye?
What I’m getting at is something similar to the fact that a human eye can’t distinguish more than 8 bits of color.

Nonsense. The human eye can distinguish millions of colors, better than a 24-bit range BUT ALSO CONSIDER that it has specific shortcomings when it comes to distinguishing _certain_ colors in adjacency sets and cannot possibly be ‘trained’ to overcome those shortcoming, and the eye misreads certain colors entirely (in part the cause of the confusion of ‘violet’ and ‘purple’); for the later case, context to make comparisons are critical.

Therefore, the final
*output* for human consumption of any image (screen or, I guess, print) need not be any greater because neither 8-bit monitors nor 8-bit eyes can handle any more (although 16-bits of *input* may be useful for intermediate processing).

Incorrect.

What is the corresponding limitation of the eye regarding resolution?

At "standard viewing distance", which has to be defined but FAPP, say 10" for an 8×11.5" print it can discern 8 lp/mm (line _pair_ per millimeter) BUT that is a lousy metric because it requires a person to read and count the lines. People don’t do that. The important issue here is that an experienced person can _sense_ the difference between 300 and 1200 lp/mm, FURTHER the issue is complicated by the concept of accutance – perceived sharpness caused by the contrast of edges, boundaries.

[…]
I realize that analog wetware is not in a nice regular matrix like digital CCDs but I’m sure taking sampling theory, Nyquist, etc into account one can come up with meaningful numbers.

As you imply and understand, THE EYE IS NOT A CAMERA. See the above.

Sorry for cut, but you are oh so wrong.

Even 32 bit colour of my Photoshop sometimes is too little for my needs. Some very fine gradients fall apart so miserably under 32 bit colour. I want 64 !!! Or 128! That would make my day.

Don wrote:

Does anybody happen to know the actual resolution of the human eye?

COW* alert!.

24 megapixels is probably a good approximation, but keep in mind a photograph is not concered with imitating the human eye, so much as creating an object for the human eye to look at. These are very different purposes.

My own guess is that 10 bit linear per channel will eventually be the standard for capture, manipulation, and display, perhaps within the next decade. Meantime 8 bit 2.2 gamma does very nicely, thank you, even for images requiring severe manipulation.

Keep in mind that the eye is very directly connected to the brain, which in turn is connected to the fingers and keyboard – get ready for a sea of words on this subject 🙂
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net

* Can Of Worms

"Mike Russell" wrote in message

Don wrote:

Does anybody happen to know the actual resolution of the human eye?

COW* alert!.
[…]
Keep in mind that the eye is very directly connected to the brain, which in
turn is connected to the fingers and keyboard – get ready for a sea of words
on this subject 🙂

Indeed, there are some serious disconnects and bypasses in the eye-brain-keyboard path. =8^}

On Wed, 19 Jan 2005 15:58:13 GMT, (Don) wrote:

Does anybody happen to know the actual resolution of the human eye?

There are limited number of cones in the fovea but it is not very meaningful to calculate a "resolution limit" for the vision based on that since the vision is composing what we see from a constant flow of "frames" and the eye constantly moves and vibrates, so the sharp spot of the eye is always there where we happen to lay our eyes on, at any given fraction of second.

The resolving power of the lens of the eye however is something like
0.1mm (so 5 line-pairs / mm). But more dense reproduction will appear
to be more sharp (even if we do not resolve lines at such density).

What I’m getting at is something similar to the fact that a human eye can’t distinguish more than 8 bits of color.

"8 bits of color" I believe would mean the same as just 256 different colors (like GIF has), but I think you refer to 8-bit/c colors, that gives something like 16.7 million different color codes. This is way more colors than that what we can differentiate from each other at any given time but the gradation that 8-bit/c provides is not enough for the vision when we compare between just two colors.

So, for the purpose of photographic imaging *output* the 8-bit/c is just barely enough to be tolerable, but e.g. for graphic art it is not enough, things like large (wide) gradations with small color difference between the endpoints will give some major trouble.

Therefore, the final *output* for human consumption of any image (screen or, I guess, print) need not be any greater because

Historically 300 ppi (pixels/inch) has been considered to be good or very good (this is about 6 lp/mm) and indeed it is not bad at all. But when we look at a reproduction that is made at 1200 ppi (about 24 lp/mm) we will notice a *huge* difference in sharpness, be it a side by side comparison or not.

Timo Autiokari http://www.aim-dtp.net

In article ,
"jjs" <john&#064;xstafford.net> wrote:

<snip>

What is the corresponding limitation of the eye regarding resolution?

At "standard viewing distance", which has to be defined but FAPP, say 10" for an 8×11.5" print it can discern 8 lp/mm (line _pair_ per millimeter) BUT that is a lousy metric because it requires a person to read and count the lines. People don’t do that. The important issue here is that an experienced person can _sense_ the difference between 300 and 1200 lp/mm, FURTHER the issue is complicated by the concept of accutance – perceived sharpness caused by the contrast of edges, boundaries.

Moreover various parts of the retina are specialized for different tasks; its resolution is fairly low outside the fovea, and although colour discrimination drops off towards the periphery the overall sensitivity to dim light gets higher. This has mostly to do with the ratio between the numbers of "rod" and "cone" cells in different regions.

The maximum angular resolution of the eye is usually quoted at about one arc-minute; from a distance of 25 cm this translates to about 75 µm.

—
Odysseus

"Mike Russell" wrote in message

Don wrote:

Does anybody happen to know the actual resolution of the human eye?

COW* alert!.

24 megapixels is probably a good approximation, but keep in mind a photograph is not concered with imitating the human eye, so much as

creating

an object for the human eye to look at. These are very different

purposes.

My own guess is that 10 bit linear per channel will eventually be the standard for capture, manipulation, and display, perhaps within the next decade. Meantime 8 bit 2.2 gamma does very nicely, thank you, even for images requiring severe manipulation.

Keep in mind that the eye is very directly connected to the brain, which

in

turn is connected to the fingers and keyboard – get ready for a sea of

words

on this subject 🙂
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net

* Can Of Worms

The limit appears to be the wavelength of visible light and the distance from the eye:
http://tinyurl.com/5uf8v

Peadge 🙂

On Wed, 19 Jan 2005 19:15:08 GMT, "Mike Russell" wrote:

Does anybody happen to know the actual resolution of the human eye?

COW* alert!.

….

* Can Of Worms

Whoops, I did it again! ;o)

24 megapixels is probably a good approximation, but keep in mind a photograph is not concered with imitating the human eye, so much as creating an object for the human eye to look at. These are very different purposes.

Yes, I realize that but I do have a hidden agenda.

Namely, while I archive my maximum bit-depth and optical resolution scans as "digital negatives", for the purposes of viewing I create images with only 8-bits of color per channel.

I was just wondering what would be the equivalent resolution I should use, beyond which resolution the eye would see no difference. Of course, current display technology may not be there yet, but eventually the screens will get to the point where we will no longer be able to discern individual pixels anymore. That’s the resolution I’d like to use (I think…).

I do realize this is an "elastic" question because there are many variables (such as viewing distance, human perception "oddities", etc) but there are many variables regarding color perception too and yet there is rule-of-thumb (although I see there are people who question it).

Keep in mind that the eye is very directly connected to the brain, which in turn is connected to the fingers and keyboard – get ready for a sea of words on this subject 🙂

How right you are! ;o) I expected, maybe, one response – if I was lucky – but 24-hours later and there is a whole thread!

Don.

On Wed, 19 Jan 2005 10:19:26 -0600, "jjs" <john&#064;xstafford.net> wrote:

Does anybody happen to know the actual resolution of the human eye?
What I’m getting at is something similar to the fact that a human eye can’t distinguish more than 8 bits of color.

Nonsense. The human eye can distinguish millions of colors, better than a 24-bit range BUT ALSO CONSIDER that it has specific shortcomings when it comes to distinguishing _certain_ colors in adjacency sets and cannot possibly be ‘trained’ to overcome those shortcoming, and the eye misreads certain colors entirely (in part the cause of the confusion of ‘violet’ and ‘purple’); for the later case, context to make comparisons are critical.

Yes, I do realize there are exceptions, but I believe 8-bits of color per channel could be described as a reasonable compromise, although this was probably influenced – at least in part – by the fact that current technology is based on 8-bit bytes so, as you say, this "rule" may fall short in absolute terms.

And, as I mention, we still work with 8-bits per channel displays (viewing a 16-bit image at 1600 magnification is quite revealing!)

Also, I do make a distinction between input and output resolution and color depth, and I also had a hidden agenda. (Please see my response to Mike for more details.)

Don.

On Wed, 19 Jan 2005 21:56:50 +0200, Timo Autiokari
wrote:

Does anybody happen to know the actual resolution of the human eye?

There are limited number of cones in the fovea but it is not very meaningful to calculate a "resolution limit" for the vision based on that since the vision is composing what we see from a constant flow of "frames" and the eye constantly moves and vibrates, so the sharp spot of the eye is always there where we happen to lay our eyes on, at any given fraction of second.

As I mentioned, I do realize the complexities. (I also seem to remember reading somewhere that our peripheral vision is much more sensitive to movement than the sharp spot.)

However, I was really after a general "rule of thumb" where the perception of detail levels off (see below)

Therefore, the final *output* for human consumption of any image (screen or, I guess, print) need not be any greater because

Historically 300 ppi (pixels/inch) has been considered to be good or very good (this is about 6 lp/mm) and indeed it is not bad at all. But when we look at a reproduction that is made at 1200 ppi (about 24 lp/mm) we will notice a *huge* difference in sharpness, be it a side by side comparison or not.

I am primarily concerned with displays. (Please see also my response to Mike.)

Let me rephrase the question by turning it around:

In your estimation, what resolution should an "average sized" monitor have in order for us to no longer be able to see individual pixels
e.g., high contrast diagonal lines such as "/" will appear smooth?

I would like to use that resolution as my target (output) resolution for the purposes of viewing and so be "future-proof". (The "digital negatives" will, of course, be archived at the optical resolution of the scanner.)

Don.

"Don" wrote in message

[…] but
eventually the screens will get to the point where we will no longer be able to discern individual pixels anymore. That’s the resolution I’d like to use (I think…).

Fear not. The natural consequence of the aging majority guarantees that pixels will be invisible regardless of monitor technology.

"Don" wrote in message

Let me rephrase the question by turning it around:

In your estimation, what resolution should an "average sized" monitor have in order for us to no longer be able to see individual pixels
e.g., high contrast diagonal lines such as "/" will appear smooth?

300 pixels-per-inch will do it.

But to get a better answer, you might want to go to an engineering group where you might find how likely it will ever be that we have 300 pixel-per-inch monitor for the masses

One more thing – Postscript Displays. Remember the neXt computer?

In article ,
"jjs" <john&#064;xstafford.net> wrote:

One more thing – Postscript Displays. Remember the neXt computer?

I’m not sure how that’s relevant, but I thought it might be worth pointing out that the Quartz display engine in Mac OS X — which is partly based on the NeXT’s OS — puts a variant of PDF on the screen, having many of the same advantages as Display PostScript did.

—
Odysseus

On Thu, 20 Jan 2005 09:41:28 -0600, "jjs" <john&#064;xstafford.net> wrote:

Let me rephrase the question by turning it around:

In your estimation, what resolution should an "average sized" monitor have in order for us to no longer be able to see individual pixels
e.g., high contrast diagonal lines such as "/" will appear smooth?

300 pixels-per-inch will do it.

Thanks!

But to get a better answer, you might want to go to an engineering group where you might find how likely it will ever be that we have 300 pixel-per-inch monitor for the masses

Regardless of the current (seemingly insurmountable) technological challenges I’m sure it’s just a question of time. A few years ago the same was said about 8-bit per channel color. Or GB hard drives. Or on-the-fly 3D engines. Or 5+1 sound. Or… I think I can stop now. ;o)

Don.

"Don" wrote in message

Regardless of the current (seemingly insurmountable) technological challenges I’m sure it’s just a question of time. […]

Your point is well taken. Such issues are, in part, why I still shoot MF and LF film when the job covers the expense. If you are interested in posting megafiles on the web you might go to http://www.caldwellphotographic.com/. Also http://www.tawbaware.com/maxlyons/gigapixel.htm. Or touch base with me. Arbitrarily large images for the web has been a project of mine for years. Finally, for another see www.keyhole.com (which at the moment is unavailable for some reason.)

I’m hoping my next grant will cover two Apple 30" monitors that I can put side-by-side.

On Fri, 21 Jan 2005 09:21:41 -0600, "jjs" wrote:

"Don" wrote in message

Regardless of the current (seemingly insurmountable) technological challenges I’m sure it’s just a question of time. […]

Your point is well taken. Such issues are, in part, why I still shoot MF and LF film when the job covers the expense. If you are interested in posting megafiles on the web you might go to http://www.caldwellphotographic.com/. Also http://www.tawbaware.com/maxlyons/gigapixel.htm. Or touch base with me. Arbitrarily large images for the web has been a project of mine for years. Finally, for another see www.keyhole.com (which at the moment is unavailable for some reason.)

I’m hoping my next grant will cover two Apple 30" monitors that I can put side-by-side.

Thanks for the links!

It’s still early days here but I’m certainly marking this message a keeper.

Don.

On Wed, 19 Jan 2005 15:58:13 GMT, (Don) wrote:

Does anybody happen to know the actual resolution of the human eye?

This book is a good modern introduction to human visual processing, linked with art:

http://www.ransen.com/reviews/VisionAndArt.htm

On Tue, 01 Feb 2005 08:21:05 +0100, Owen Ransen
wrote:

On Wed, 19 Jan 2005 15:58:13 GMT, (Don) wrote:

Does anybody happen to know the actual resolution of the human eye?

This book is a good modern introduction to human visual processing, linked with art:

http://www.ransen.com/reviews/VisionAndArt.htm

Thanks!

Don.

"Owen Ransen" wrote in message

On Wed, 19 Jan 2005 15:58:13 GMT, (Don) wrote:

Does anybody happen to know the actual resolution of the human eye?

This book is a good modern introduction to human visual processing, linked with art:

http://www.ransen.com/reviews/VisionAndArt.htm

Yes, that’s Margaret Livingston’s book. She is definitely one to watch. She publishes regularly publishes in the journals. New things every year.