How does the dynamic range of the human eye compare to that of digital cameras?

Question

According to DxO tests, cameras have 10 to 12 stops of dynamic range. Is that correct? Noise can completely screw some lowers values (easily resulting in loss of some stops).

Also Norman Koren says that a digital camera's original dynamic range can be 9 to 11 stops, but prints have "only" 6.5 stops.

In a section on dynamic range, Wikipedia says the human eye has a contrast ratio of around 6.5 stops. If that is the case, why is the human eye clearly much better than cameras to record scenes with high dynamic range?

Asked by Paolo

Answer

This is a very good question, and the answer could fill hundreds of pages - and, in fact, the answer already DOES fill hundreds of pages.

The short answer is that the figures you are citing to not agree with apparent reality because the commonly quoted figures are wrong :-). Read on ...

Much is available on the internet on this subject and the quality is, as ever, widely variable. There is also a lot of parroting of "facts" between sites and figures like those in Wikipedia seem common enough BUT there are some very reasoned arguments which seem to suggest that the Wikipedia figure is extremely wrong and underestimates the figure very substantially.

It's important to note that the eye acts as a contrast detector rather than an absolute level detector (such as a digital camera sensor uses) so comparisons need care.

With irising, chemical adaptation and every other trick it can pull it seems that the absolute dynamic range of the whole eye system is well over 20 stops. As each stop is a factor of 2, that's 2^20 or about "well over 1,000,000:1". At the top end, the sun is too bright!!!. At the bottom end the dark adapted eye can detect a single photon. A D3S (better performance than a D4) may have trouble with that. (Note that that is not EVERY photon - when you get down to the few photons per second level a lot of then will hit non sensor areas and not be detected. BUT when one does strike a sensitive retina area it will produce asignal that can be recorded.)

But, I digress :-). An extremely good (it seems) page that discusses eye dynamic range and more is

• Notes on the Resolution and Other Details of the Human Eye.

Paragraph headings are worth noting:

Notes on the Resolution of the Human Eye
Visual Acuity and Resolving Detail on Prints
How many megapixels equivalent does the eye have?
The Sensitivity of the Human Eye (ISO Equivalent)
The Dynamic Range of the Eye
The Focal Length of the Eye

The writer argues that the dynamic range of the eye without changing sensitivity by adaptation or irising is about 1,000,000:1 in low light conditions. ie as greatas the "well over" lower limit mentioned above. Then he justifies this claim as copied below. This sounds fairly convincing at first glance. There may be flaws in the argument, but it seems OK, and this does not mean that it applies in all light levels.

• Here is a simple experiment you can do. Go out with a star chart on a clear night with a full moon. Wait a few minutes for your eyes to adjust. Now find the faintest stars you can detect when the you can see the full moon in your field of view. Try and limit the moon and stars to within about 45 degrees of straight up (the zenith).

  If you have clear skies away from city lights, you will probably be able to see magnitude 3 stars.

  The full moon has a stellar magnitude of -12.5.

  If you can see magnitude 2.5 stars, the magnitude range you are seeing is 15.

  Every 5 magnitudes is a factor of 100, so 15 is 100 * 100 * 100 = 1,000,000.

  Thus, the dynamic range in this relatively low light condition is about 1 million to one, perhaps higher!

But, here's a suggestion from me for an experiment at normal daylight light levels.

• Find a scene that has a good mixture of dark areas and very bright areas - ideally wity some dark areas a isolated islands near islands of brightness. An example may be sunlight shining through trees into a heavily shaded area - a few caelets or deeply shaded areas will help.

• Allow your eyes to adapt to the general lighting level - do not stare at the bright spots near where the sun is shining through and do not focus on any especially dark areas.

• Note how well you can see detail in the darkest of dark areas - at what level of darkness does is fade to black.

• Try the same with bright areas - as you look toward the sun there will be a place where details washes out and you cannot reasonably see more.

• Cast your eyes to and fro across the scene between dark and light to try to stop your adaptation mechanism changing f-stop on you.

• Now, Take photos of the scene. Expose "correctly" and then so the darkest areas that you could see can be seen in the photo and then so that the brightest highlights you could distinguish are no washed out.

• If you have the equipment, take an HDR photo with maximum fstop variation between photos. (My Sony A77 allows 5ev steps.)

My experience is that my eye can always see a wider brightness range than my camera (Minolta 7Hi, A200, 5D, 7D, A700, A77, other)

On maximum HDR image (10 ev range between centres) my eye can see as well as or better than the camera.

The area where this does not APPEAR to be so is in extremely low light when I may need to allow the eye to integrate (which it does for up to about 4 seconds!) whereas I can look at a low light photo and see the image immediately. The fact that I may have needed a 10 second exposure is then irrelevant for viewing.

---

Other variably good stuff:

• Wikipedia - human eye
• Wikipedia - dynamic range
• The Online Photographer - Dynamic Range
  • more re photos than eyes, but good.
• Making fine prints in your digital darkroom - Tonal quality and dynamic range in digital cameras
• HDR FAQ
• Discussion. Good.
• Panoramas - dynamic range discussion
• Cameras and Vision
  • Good. Claims day 15,000:1 and night 10,000,000:1.
• Cameras vs the human eye
• What is the dynamic range of the human eye
  • amateur experts opine.
• Eye and camera differences

Answered by Russell McMahon

Check more discussion of this question.

Is it possible to be colour-blind and still be a good photographer?

Question

Is it possible to be colour-blind (or color-blind, in the US) and still be a good photographer?

Are there any steps one can take to mitigate the effects of colour-blindness? Can you point me to any great photographers who are colour-blind?

The obvious answer which comes to mind is to shoot black and white, but is that really a sensible answer? Does colour-blindness affect one's perception of greyscales?

Asked by AJ Finch

Answer

I'm color blind (or rather have a color vision deficiency). Specifically my eyes are less sensetive to red light than other colors.

I can't really say that I suffer from it. It makes it harder to pick lingonberries, and I have problem reading tiny red text on a black background, but that's about it.

I might perhaps photograph red objects differently, as I don't experience them as brightly as most do. Post processing images and adjusting white balance is not a problem, though. I am used to how red things look like, so when I adjust the image so that they look right, it will look right to others too even if they actually experience the image differently.

(Yes, I know that my avatar image is orange. I don't think that it's a nice grayscale... :)

Answered by Guffa

Check more discussion of this question.

What is it called when an object appears to be the same size with the eye and through the camera viewfinder,?

Question

I have a Canon 18-135 lens. I am looking into the camera viewfinder with my right eye and not through the viewfinder with my left. I start from 18mm and keep zooming in till I see a particular object as the same size with both the eyes.

I read the focal length to be just above 50 mm (say, 55mm). What is special about this 55mm with reference to the object I was focussing on?

Answer

There's a specification on (d)SLR bodies called viewfinder magnification; this refers to how large an object appears in the viewfinder when a 50mm lens is mounted and focused at infinity.

On mid-range DSLRs, which typically have around 0.95x magnification, an object will appear to be life-sized at 52.6mm. With entry-level DSLRs, you might have around 0.8x magnification, so you'd have to zoom in to 62.5mm to get a 1:1 magnification. I'm betting your camera has somewhere around 0.9 to 0.95x magnification.

This has very little to do with the object, except that the front of the camera is slightly closer to the object. With far-away subjects (landscapes, etc), the distance between your eyes and the front of your camera won't matter much, but close subjects will appear larger to the camera than to your eye even with a 1:1 magnification.

Check more discussion of this question.

How to capture the scene exactly as my eyes can see?

Question

What settings of my DSLR camera will emulate the scene exactly as I can see through my naked eyes?

I think it's not possible to get the contrast and colors exactly as my eyes can see, and it may vary from person to person. So, I am more interested in focal length of the lens. If anyone can give more insight beyond focal length, I will be glad to know.

For example, if I am standing on the seashore and want to capture the sunrise, what should be the focal length so that I can cover the angle of view which my eyes can see, and so the size of the objects in the photo will be precisely like my eyes perceive it?

My camera is an APS-C Canon EOS 1000D. I have 50mm 1.8 and 70-300mm Sigma , Can it be achieved through this equipment lens? Till now, I have not achieved or been satisfied with what I see and what I get.

Answer

Well, I hate to break it to you, but you can't exactly emulate your eyes. There's a few reasons, let me explain.

1. Humans see much higher resolution in the central fovia (center part of our eyes) than near the edges. Cameras have uniform resolution everywhere.
2. The dynamic range is handled differently between cameras and humans. I can't explain it, but a scene appears to have more dynamic range to a human than a camera, although technically a camera has more dynamic range.
3. Humans see in 3 dimensions.
4. Humans change their focal points very quickly, to the point that we don't actually notice the out of focus portions of most scenes.

Notwithstanding all of that, let me just say that it depends if you are wanting to focus on a specific area, or on the larger scene around. If you want the specific area, you probably should go about 150mm or so. As for a dramatic landscape, something more like a 24 will get your entire field of view. A commonly cited number is 50mm, which will let you see the higher resolution portion of your eyes and then some, but not the entire field, and is usually a good compromise. (All of these assume you have a full framed camera, if yours is a crop sensor, please divide by the appropriate factor)

Check more discussion of this question.

How many colors and shades can the human eye distinguish in a single scene?

Question

How many distinct colors, shades, hues, and tints can the average person distinguish in a single scene? In other words, what's the theorectical bit-depth required to be sure of recording a photograph with all of the visual information a human would perceive, assuming perfect equipment?

I've seen answers ranging from 200,000 to 20,000,000, and it's hard to sort out authority. And the term "color" is ambiguous — is just hue meant, or are differences in saturation and lightness also included? (For the purposes of this question, everything is needed, although it'd be cool to have them separately. And since we're more sensitive to green and yellow, should more bits be devoted to those hues in some way?)

The difference in possible answers is staggering — two hundred thousand can fit nicely in 18 bits — or just six bits per channel, which is obviously a lot less than the ubiquitous eight-bits/channel image formats today. (Are these formats just using an inefficient encoding? It seems like that answer must be too small.) But if it's 20 million just including hue, and we take one of the upper numbers for distinguishable luminosity levels, that's about 37 bits. (Which in turn raises the question: are formats which use 48 bits, 16 per channel, actually way bigger than necessary?)

Finally, does the number of perceivable colors significantly differ from the maximum number visible at once under ideal conditions? (For example, due to dynamic range limitations, or to our natural tendency to "auto white balance"?) If so, could this simply be encoded as a scene-wide compensation?

(I realize there may be reasons for having more bits in an input or working space than needed for distinguishing colors in the final output. That's probably a whole different question.)

Answer

I'll base my answer on the work done by CIE, which began in the 1930's, and progressed again in the 1960's, with some algorithmic and accuracy improvements to formula over the last couple decades. When it comes to the arts, including photography and print, I think that the work done by the CIE is particularly relevant, as it is the basis of color correction and modern mathematical color models and color space conversion.

The CIE, or Commission internationale de l'éclairage, in 1931 established the "CIE 1931 XYZ color space". This color space was a plot of full purity color, mapped from 700nm (near-infrared red) through 380nm (near-UV), and progressed through all the wavelengths of "visible" light. This color space is based on human vision, which is a tri-stimulus created by the three types of cones in our eyes: short, medium and long wavelength cones, which map to 420-440nm, 530-540nm, and 560-580nm wavelengths. These wavelengths correspond to blue, green, and yellow-red (or orangish-red) primary colors. (The red cones are a bit unique, in that their sensitivity has two peaks, the primary one in the 560-580nm range, and also a second one in the 410-440nm range. This double peaked sensitivity indicates that our "red" cones may actually be "magenta" cones in terms of actual sensitivity.) The tristimulus response curves are derived from a 2° field of view of the fovea, where our cones are most concentrated and our color vision, under medium to high lighting intensity, is at its greatest.

The actual CIE 1931 color space is mapped from XYZ tristimulus values, which are generated from red, green, and blue derivatives, which are based on actual red, green, and blue color values (additive model.) The XYZ tristimulus values are adjusted for a "standard illuminant", which is normally a sunlight balanced white of 6500K (although the original CIE 1931 color space was created for three standardized illuminants A 2856K, B 4874K and C 6774K), and weighted according to a "standard observer" (based on that 2° foveal field of view.) The standard CIE 1931 XYZ color plot is horshoe-shaped and filled with a "chromaticity" diagram of pure 'colors', covering the hue range from 700nm through 380nm, and ranging in saturation from 0% centered at the white point to 100% along the periphery. This is a "chromaticity" plot, or color without regard to intensity (or color at maximum intensity, to be most accurate.) This color plot, according to some studies (references pending), represents about 2.38 million colors that the human eye can detect under moderately high intensity lighting approximately the same color temperature and brightness of daylight (not sunlight, which is closer to 5000k, but sunlight + blue sky light, about 6500k.)

---

So, can the human eye detect only 2.4 million colors? According to the work done by the CIE in the 1930's, under a specific illuminant that equates to the intensity and color temperature of daylight, when factoring in only the 2° of cones concentrated in the fovea of our eyes, then it seems we can indeed see 2.4 million colors.

The CIE specifications are limited in scope, however. They do not account for varying levels of illumination, illuminants of differing intensity or color temperature, or the fact that we have more cones spread across at least a 10° area of our retinas around the fovea. They also do not account for the fact that peripheral cones seem to be more sensitive to blues than the cones concentrated in the fovea (which are primarily red and green cones).

Refinements to the CIE chromaticity plots were made in the '60's and again in 1976, which refined the "standard observer" to include a full 10° color sensitive spot in our retinas. These refinements to CIE's standards have never come into much use, and the extensive color sensitivity research that has been done in relation to CIE's work has been largely limited to the original CIE 1931 XYZ color space and chromaticity plot.

Given the limitation of color sensitivity to only a 2° spot in the fovea, there is a strong likelihood that we can see more than 2.4 million colors, particularly extending into the blues and violets. This is corroborated by the 1960's refinements to CIE color spaces.

---

Tone, perhaps better labeled luminosity (the brightness or intensity of a color), is another aspect of our vision. Some models blend chromaticity and luminosity together, while others distinctly separate the two. The human eye contains a retina composed of both cones..."color" sensitive devices, as well as rods, which are color-agnostic but sensitive to changes in luminosity. The human eye has about 20 times as many rods (94 million) as it does cones (4.5 million). Rods are also about 100 times as sensitive to light as cones, capable of detecting a single photon. Rods seem to be most sensitive to the blueish-green wavelengths of light (around 500nm), and have lower sensitivities to reddish and near-UV wavelengths. It should be noted that a rods sensitivity is cumulative, so the longer one observes a static scene, the clearer the levels of luminosity in that scene will be perceived by the mind. Rapid changes in a scene, or panning motion, will reduce the ability to differentiate fine tonal gradation.

Given the rod's far greater sensitivity to light, it seems logical to conclude that humans have a finer, and distinct, sensitivity to variations in light intensity than they do to changes in hue and saturation when one observes a static scene for a time. Exactly how this factors into our perception of color and how it affects the number of colors we can see, I can't exactly say. A simple test of tonal sensitivity can be done on a clear day's evening, just as the sun sets. The blue sky can range from near white-blue to deep dark midnight blue. While the hue of such a sky covers a very small range, the tonal grade is immense and very fine. Observing such a sky, one can see an infinitely smooth change from bright white-blue to sky blue to dark midnight blue.

---

Studies unrelated to CIE work have indicated a wide range of "maximum colors" that the human eye can perceive. Some have an upper limit of 1 million colors, while others have an upper limit of 10 million colors. More recent studies have shown that some women have a unique fourth cone type, an "orange" cone, that could possibly extend their sensitivity to 100 million, however that study counted both chromaticity and luminosity in their calculation of "color".

That ultimately begs the question, can we separate chromaticity from luminosity when determining "color"? Do we prefer to define the term "color" to mean the hue, saturation, and luminosity of the light we perceive? Or is it better to separate the two, keep chromaticity distinct from luminosity? How many levels of intensity can the eye really see, vs. how many distinct differences in chromaticity? I am not sure these questions have actually been answered in a scientific way yet.

---

Another aspect of color perception involves contrast. It is easy to perceive a difference in two things when they contrast well with each other. When trying to visually determine how many "colors" one sees when looking at varying shades of red, it can be rather difficult to tell if two similar shades are different or not. However, compare a shade of red with a shade of green, and the difference is very clear. Compare that shade of green in sequence with each shade of red, and the eye can more easily pick up the differences in the red shades in peripheral relation to each other as well as in contrast with the green. These factors are all facets of the vision of our mind, which is a far more subjective device than the eye itself (which makes it hard to scientifically gauge color perception beyond the scope of the eye itself.) Given a setting with appropriate contrast, one may be able to detect far more distinct colors in context than a setting without any contrast at all.

---

When discussing the number of colors perceptible to the human eye, I tend to refer to the 2.4 million colors of the CIE 1931 XYZ color space. It is a fairly solid, scientifically founded number, although I do admit it may be limited in context. I think it may be possible for the human eye to be sensitive to 10-100 million distinct "colors" when referring to both chromaticity and luminosity.

Check more discussion of this question.

Why are there no dark yellows, or bright violets?

Question

In his book The Photographer's Eye, photographer and author Michael Freeman says:

Another consideration is relative brightness. Different hues are perceived as having different light values, with yellow the brightest and violet the darkest. In other words, there is no such thing as a dark yellow, nor is there a light violet; instead, these colors become others — ochre, for example, or mauve.

---

Update: Freeman is clearly talking about something more serious than the labeling of colors. In The Photographer's Eye, the above quote is part of a relatively small section, but the same concept occurs throughout an earlier book of his, Mastering Color Digital Photography. The idea seems to be that when darkened, yellow loses the essential qualities that make it yellow, and when made bright violet loses the essential qualities that make it violet — in a way that red or blue do not. These qualities are clearly more than their position in a color space, and they're also clearly more than the name applied.

My earlier discussion (the next few paragraphs) was about how I've seen this in practical effect, and how I think you probably can too if you haven't thought about it before. But the question I still have is why?

Some of the answer may be cultural, but if it were entirely arbitrary, it seems odd that these particular effects would be claimed in reverse for colors which are direct contrasting colors on the color wheel. That seems to imply some technical reason beyond any sort of thing like "purple is royal because of the rareness of the dyes in ancient times."

---

And, particularly with yellow, I've seen this to be true. If you've ever worked with the 16-color VGA pallette, you know what I'm talking about — in fact, the HTML 4 spec names dark yellow "olive". I realize that the other colors have, well, colorful names (lime, for example) but who ever heard of a yellow olive? And this isn't something wacky with the restricted colors available — it's what you get when you take pure red and pure green mixed, and then cut the brightness in half. I don't think this is just a matter of naming — I remember being frustrated with the inability in a 16-color scheme to make a dark yellow that reads as yellow.

I assumed that this was basically due to a limitation of the RGB color model — that the color exists, but we just can't get to it in that way. (Edit: this appears to be true of violet, in a scientific sense; it can only be approximated with purple, which is a mix of red and blue. See this Wikipedia link provided by Evan Krall in the comments below. There's something called the Bezold–Brücke shift involved, which might be part of the answer to this question.) But Freeman suggests something more about our perception than about the color model.

What's going on here?

---

Postscript: my six-year old, on her own accord, sorted her markers by "how bright the colors are":

I think Goethe would be pleased.

Answer

I think it's a bit more than simply saying "we have other names for those colours." Yes, there is a cultural component. If English didn't have the word "pink" we may very well refer to a colour "light violet." Some languages don't even distinguish between blue and green. But I believe in the case of Yellow, that the way our brain interprets colour means that the very best we can do with "dark yellow" is call it "gold."

Think about describing colour with "-ish" for example. We can have a bluish-green, or an orangish-yellow, but imagine the color yellowish-blue. It doesn't exist. The same with greenish-red. (Scintillating colour-changing fabrics notwithstanding.)

The "pure" colours our eyes perceive and our brains interpret are yellow, blue, green, red, and possibly brown. (See opponent process theory.) Other colour names are cultural and variations on those. For example, orange is a reddish yellow or yellowish red, pink is a pale bluish-red, violet a reddish-blue. So we find it difficult to imagine a "dark yellow" because our eyes and brain are more likely to interpret it as a "dark desaturated green" or possibly a "greenish brown."

Check more discussion of this question.

How to create an eye-path?

Question

Reading about photography, I have now and then stumbled on recommendations to "create a path for viewer's eye", or to "lead it through the picture" without any specific guidelines how to achieve that.

How can a photographer influence where the eye lands, how it travels and where it stops on its way through the picture?

Answer

The human eye seeks the light, and usually locates the brigthest spot in the image. If there is one bright spot, that's usually the place we start looking.

There are no definitive rules in photography, and I'm not trying to say that you always need to let the subject be the "bright spot" in the image, but if you want to lead the viewer to the most important part immediately, you should make it be brighter than it's surroundings.

When we look around our eyes tend to follow lines and connected "paths". There are unlimited ways of how to create such paths, but try using "lines" in the environment. It can be tree branches, buildings, roads,...anything that seems to be connected, but not cluttered. Something with contrasts, that's easy for our eyes to identify and "follow around".

I really enjoyed Michael Freeman's book The Photographer's Eye, in which he explains this topic well.

To illustrate how our eyes search bright spots, and follow lines, I have linked to a couple of images from my Flickr page.

Here is an image from the St. Peters church. What is the first you notice in the picture, and how far does the eye lead you automatically?

Bright spot in St. Peters Church

Take a look at the image of the bridge in the clouds, and notice what parts of the image you see by letting your eyes guide you automatically.

Leading lines on Bridge in the clouds image

When I'm looking at the picture from St. Peters Church, my eyes goes directly to the window, and then following the light down to the group of people. It's no path for the eyes to follow from there, which actually works in this picture: For me the most interesting thing is what's happening just there where the light hits the people. ...and who is that enlightened person which everyone is gathering around? ;)

In the other image, the bridge it self is the main subject. There are not much contrast in the image, so my eyes does not lock on a specific parts of the image. Instead the eyes "grab on" to something and follows the lines around the picture from there on. When I'm viewing this image, my eyes basically explores the entire frame, ending up in the center of the image where all the lines end.

Check more discussion of this question.

Technically, why is the out of focus area blurred more when using a bigger aperture?

Question

I'm wondering, technically, why and how does the out of focus areas blur more when using a bigger aperture. I think it'd help a lot if I presented a problem that's been driving me nuts for a long time:

If you move an object at a certain speed, the human eye always sees the same amount of motion blur, no matter what amount of light is currently present. This should lead to the fact that human eye perceives the world always at exactly the same "shutter speed", let's set this for example to 1/50 sec. Therefore, it can only regulate the amount of light by adjusting the "aperture."

It's a well-known fact that human eye can control the aperture by pupils dilating and constricting. As the wikipedia says:

Computing the f-number of the human eye involves computing the physical aperture and focal length of the eye. The pupil can be as large as 6–7 mm wide open, which translates into the maximum physical aperture. The f-number of the human eye varies from about f/8.3 in a very brightly lit place to about f/2.1 in the dark.

The problem with the aforementioned is that from what I've tested, I always see out of focus areas in the same amount of blur. Try it out yourself:

1. Close one of your eyes.
2. Place your finger about 30 cm from the open eye, or whatever distance you can easily focus to.
3. Keep looking at the finger, focusing at it, but noticing the background blur.

Repeat the above in various light conditions - dark and light areas (evening and midday). You will probably notice that you always get the same amount of background blur, but if you did this with your camera, the blur would be noticeably different (less/more blur).

Which leads me to ask: how does this aperture thing work, why does it create a blur from the technical point of view and does it also apply to eyes, or is it just a "failure" in the camera lenses we've come to like and never wanted to "fix"?

Answer

I'm going to crib from my answer to an earlier question on aperture:

When the aperture is very small, the admitted light is highly "collimated", which is a fancy way of saying "all the rays are nicely parallel to each other". This results in a sharp focus for all the light that comes in. When the aperture is more open, only the rays which closely match the focus point are collimated — which means that whatever you've focused on is sharp, but farther or closer parts of the scene will be increasingly blurry.

Basically, the smaller the aperture, the more restricted-to-exactly-in-focus the light is. A bigger aperture lets in more light, but the "price" is that it's less controlled.

This surely happens with the human eye as a lens as well. I think it's just really hard to control your experiment, since you can't actually snap a picture to compare side by side. In the time between evening and midday — or even in the half hour it takes your eyes to acclimate to a dark room — you lose the perfect memory of how much blur there was. This is further complicated by the fact that your brain is working very hard to correct all defects from the eyes and present a mental model of the entire world in perfect focus. (That's what the brain part of the human vision system does.)

It's very hard to look at just one spot; your eye flicks around subconsciously, and builds a perfect image from one which is really only sharp in the center. This adds another huge complication — not only is the lens of the eye a relatively simple system with a lot of aberrations, the sensor is irregular. Or rather, it's highly specialized. The central area is called the fovea, and that's only about 1mm in diameter — and the most sharp part, the foveola, is only 0.2mm. That's where really sharp vision comes from. But this area doesn't contain any rods (the cells sensitive to dim light), so this sharp area is not involved at all when you're in dim light. This makes a simple comparison with camera systems basically impossible.

On top of that, there's another flaw in your basic assumptions — the idea that the human eye sees the same amount of motion blur no matter the amount of light. Actually, the input is actually integrated over time, and the amount of time does increase in lower light levels. And, "exposure" is actually controlled in another way: the sensitivity is boosted in the darkness — the effective equivalent of auto-ISO.

So, to get to the direct question: it's the nature of optics, and so it also applies to our eyes. But our eyes are a different kind of system than a camera and lens. The human vision system features a simple lens, a complicated sensor, very complicated instantaneous post-processing, and an incredibly complicated storage and retrieval system. A camera generally uses a sophisticated lens, a comparatively straightforward sensor matrix, and comparatively straightforward post-processing (until computational photography comes into its own — whether Lytro succeeds this year or someone else five years from now). And the memory system is bit-for-bit perfect — not like human memory in the least.

Whether this difference is something we "like" and don't want to fix is a matter of interpretation. Certainly the idea of depth of field is in our artistic/visual vocabulary as a society; whether it will stay that way in a hundred years is a matter of speculation. (My guess is yes.)

Check more discussion of this question.