Naked Science Forum
General Science => General Science => Topic started by: neilep on 19/06/2010 17:32:11
-
Dearest Peeps Of Scholarly Knowledgeaby Knowing Stuff,
As a sheepy I of course am very photogenic.....I recently posed for PlaySheep magazine and their sales rocketed !....so..being an authority on photo stuff ewe'd think I know all that there is to know about mega-pixels eh ?...."yes" I hear ewe all say......well...*shock horror* there's one thing I do not know......and that is the megapixelage/resolution of my eye.
Look here's a Sony camera
[ Invalid Attachment ]
A Sony Camera Yesterday*
Nice eh?..8.1megapixelsof Sony Joyness .....
Now here is my eye !
[ Invalid Attachment ]
....Nice eh ?.....
But what resolution is my eye ?..how many mega-pixels is it?..I reckon it has got to be at least 4 !!
whajafink ?
Hugs and shmishes
mwah mwah mwah !!
Neil
Eye Owner...two in fact
xxxxxxxxxxxxxxxxxxxxxxxx
*Other cameras of other brands of equal quality are also available but if SONY wish to outfit my entire home with top notch SONY kit as a freebie then I will gladly rebuke the "Other " brands statement !
-
I think that is a super question.. and seriously do we see in mega pixels? I was not even sure I was aware of all the facts... I knew they were dots per inch etc.. but this helped and still makes me wonder if Our eyes could even be compared in pixels??? Makes me curious...
Read this....
http://www.digital-slr-guide.com/define-megapixels.html
Trying to Define Megapixels?
Let me help you out: I'm going to define megapixels in a way that should clear up a lot of confusion.
Since the very first digital camera, this one term has been shrouded in mystery. It has been the defining feature on digital cameras for years and has been built up and hyped to no end.
The megapixel race has boiled down to a catch phrase: "more is better".
It makes sense why camera makers and retailers aren't falling over themselves to clearly define megapixels to consumers: a megapixel number makes it easy to compare two different cameras.
"Our camera has 10 megapixels while our competitor's only has 8. I'm sure you can tell which one is better."
And - surprise, surprise - the more megapixels a camera has, the more it costs. Of course a salesperson is going to tell you that a camera with more megapixels is going to take better photos.
But what are these megapixels really good for? In the following paragraphs, you'll find out.
In The Beginning
The foundation of megapixels is the lowly pixel.
A pixel is one dot of information in a digital photograph. Digital photos today are made up of millions of tiny dots (Mega = Million).
This means that a 10 megapixel image contains approximately 10 million pixels, while a 14 megapixel image contains 14 million pixels.
Since a photo has a rectangular shape, the dimensions of one side aren't equal to the other. If we assume that we're looking at photo in landscape orientation:
* A 10 megapixel photo measures 3888 pixels wide by 2592 pixels high
* A 14.5 megapixel photo measures 4672 pixels wide by 3104 pixels high
If you take the width and multiply it by the height, you get the total number of pixels that make up the digital image:
* 3888 x 2592 = 10,077,696 pixels = 10 megapixels
* 4672 x 3104 = 14,501,888 pixels = 14.5 megapixels
This is just the tip of the iceberg - there's a lot more information required to define megapixels.
Is More Better?
So a camera with more megapixels takes clearer photos right?
After all, if one camera is capturing 14 million pixels and another is only getting 10, then the photo with 14 million pixels should look better.
Not exactly.
While a digital photo that contains 14 million pixels is physically larger than one with only 10 million, when viewed and printed at small sizes they are hard to tell apart.
Can you tell which of these two photos has 10 megapixels and which one has 14?
canon-eos-40d-238 pentax-k20d-287
The real notable difference is not one of quality, but one of file size: 14 megapixel cameras create larger digital files than their 10 megapixel counterparts.
A larger file size means:
* You need to purchase higher capacity memory cards (4GB or more)
* It takes longer to transfer an image from the memory card to your computer
* You need more hard drive space on your computer to store your photos
* You need a more powerful computer to organize and edit your images
* You must dramatically reduce the size of photos to send via e-mail
* It takes longer to upload the original images to an online gallery
This leads us to ask an important question: what's the point of cameras with more megapixels if image processing takes up so much time and space?
Large Print Sizes
First, the most obvious advantage:
You can print photos with more megapixels at large sizes.
Let me define this another way: if you print an 10 megapixel photo and a 14 megapixel photo at 4x6 inches (standard print size) you'll be hard-pressed to tell which one is which (just like when you compared the small images above).
But if you print both photos at 20x30, then you will see a difference in quality.
The 10 megapixel photo won't look as clear and as sharp as the 14 megapixel photo when printed at this large size.
This table shows the most common "acceptable" print sizes based on the number of megapixels.
Number of Megapixels Acceptable Print Size (Inches)
2.0 4 x 6 [standard]
3.0 5 x 7
4.0 8 x 10
5.0 8 x 12
6.0 9 x 12
8.0 11 x 14
10.0 12 x 16
12.0 16 x 20
14.0 18 x 24
Here's how to read the megapixel print size table:
* With a 10 megapixel camera, any print that you make that is 12x16 or smaller will look fantastic
* With a 6 megapixel camera, you can make high-quality prints at 9x12 or smaller
Can you print your photos larger than the acceptable size? You bet.
There's nothing stopping you from printing your 6 megapixel photos at 20x30, or even billboard size if you so desire.
But there is a catch: as you increase the size of a print above the acceptable print size, the image quality deteriorates.
A 4 megapixel photo printed at 4x6 will be perfectly clear. It will also be clear at 8x10. But a 4 megapixel photo printed at 11x14 will show a loss of image quality. The same image printed at 20x30 will show considerable loss of image quality.
BOTTOM LINE: If your goal in life is to make really large prints, then compare cameras with lots of megapixels. If you just want to print at 4x6 and e-mail photos to friends, then spending a lot on more megapixels is a bit of a waste.
More Image Cropping Options
You can now define megapixels in one way: more of them lets you make larger prints.
There is a second benefit to having a lot of megapixels in your photos: it gives you freedom to crop.
Let's say that you've taken a photo with an 8 megapixel camera - you're able to make nice 12x16 prints with this.
On a photo safari, you take a photo of an egret, but you're too far away from the bird and you don't have a telephoto lens to get up close and personal.
The primary subject of your photo is tiny. You decide to crop the shot so that the egret appears larger.
No problem...except that you can no longer print at 8x10.
You need 8 megapixels to print at 12x16 before the image starts to deteriorate. When you crop the image, you are eliminating pixels - let's say that you crop out 2 megapixels from your photo.
You wind up with a 6 megapixel photo - you can make a nice 11x14 print, but that's about it.
Now imagine that you take the same shot with a 10 megapixel camera.
With this shot, you can crop out a full 50% of the image (5 megapixels) and still make a high-quality 9x12 inch print.
But be aware that cropping and adjusting your photos takes time. In fact, it takes a lot longer to edit photos than to take them in the first place.
BOTTOM LINE: If you don't want to spend your time sitting in front of the computer editing and cropping your photos, then a camera with tons of megapixels doesn't provide you with an advantage.
Buying Tip
Let's conclude our introduction to megapixels with a quick summary of some of the reasons for and against getting a camera with more megapixels.
Get a camera with a high megapixel count if you:
* Want to make very large prints of your digital images
* Want to crop out large portions of your photos and still make large prints
Don't spend all your hard-earned money on lots of megapixels if:
* You rarely make prints larger than 4x6 inches
* You just want to upload images to an online gallery
* You enjoy sharing photos with friends via e-mail
There you have it: the mystery of megapixels has been clarified. That wasn't so hard, was it?
Now that you know what they're about, get out there and define megapixels for others so they don't have to stay in the dark!
-
I'm glad ewe like the kweschun Kareny Mam...and thank ewe for the oodles of information.....I just need to get my lil 'ole' brain round it. In the mean time, lets hope someone can comment on my original query.
-
.
Through deductive reasoning the human eye has no pixels per say.
I believe the Human Body's metabolism does not process our senses digitally.
Pixel resolution relates to the digital process of a CCD.
In the human body, the sensors chemically blend together like a fluid and are not just a "hard", turn on, shut off process.
For example, look at a small pain in the arm, you know where to approximately locate the center of the pain, also; you can not quite find exactly, the precise spot the pain ends, you do know it fades somewhere along the lines.
This is more an analog characteristic then a digital characteristic.
Knowing this, the "Pixel", realm and term, only exists in the digital world.
Here is something else look at, real film cameras, they speak of picture resolution in terms of grains not pixels.
I propose through definition that the human eye has no pixels.
.
-
Kinda my line of thinking after reading about what the pixels actually are...thanks.....
-
I'm glad ewe like the kweschun Kareny Mam...and thank ewe for the oodles of information.....I just need to get my lil 'ole' brain round it. In the mean time, lets hope someone can comment on my original query.
Your welcome....and I agree with Tommya300!
-
Not to mention that the human eye is not a very good optical system. Our brains seem to do an enormous amount of "post processing" of the actual image that's presented to the retina (which, of course, is also upside down!)
-
Not to mention that the human eye is not a very good optical system. Our brains seem to do an enormous amount of "post processing" of the actual image that's presented to the retina (which, of course, is also upside down!)
yepper absolutely.
Although we speak of imperfection it is amazing the speed that the brain actually processes the data and categorically separates the junk from the good stuff.
-
You can't directly compare the quality of digital and analogue because there is no common framework of reference. It's a bit like comparing cats and custard!
.
In the human body, the sensors chemically blend together like a fluid and are not just a "hard", turn on, shut off process.
This is more an analog characteristic then a digital characteristic.
I think Tommy hit the nail on the head. Analogue images are particular, that is they are made out of discrete units. Whereas digital images use a continuous, non-divisable range of values. If you enlarge a digital image it becomes pixelated and granular whereas an analogue image becomes blurry and indistinct.
And Geezer's point that the majority of image perception is due to the processing power of the brain also makes it difficult to directly compare the eye with a digital camera.
-
.
Through deductive reasoning the human eye has no pixels per say.
I believe the Human Body's metabolism does not process our senses digitally.
Pixel resolution relates to the digital process of a CCD.
In the human body, the sensors chemically blend together like a fluid and are not just a "hard", turn on, shut off process.
For example, look at a small pain in the arm, you know where to approximately locate the center of the pain, also; you can not quite find exactly, the precise spot the pain ends, you do know it fades somewhere along the lines.
This is more an analog characteristic then a digital characteristic.
Knowing this, the "Pixel", realm and term, only exists in the digital world.
Here is something else look at, real film cameras, they speak of picture resolution in terms of grains not pixels.
I propose through definition that the human eye has no pixels.
.
YAYYYY !!
Thank ewe Tommy for your wonderful answer.
I "see" your point. I think we do process imagery just biologically as ewe have indicated.
I sheepose I was hoping that an indication of a digital number might be possible.....ie..if one could replicate the human image sensing in a digital format.
Thank ewe very much
-
Hang on!
The eye is digital.
The human retina has about 70 million receptor cells so it's reasonable to say that it has the equivalent of about 70Mp
John has got this bit
"I think Tommy hit the nail on the head. Analogue images are particular, that is they are made out of discrete units. Whereas digital images use a continuous, non-divisable range of values. If you enlarge a digital image it becomes pixelated and granular whereas an analogue image becomes blurry and indistinct."
pretty much totally backwards.
Digital images are particular; the particles are called pixels.
Digital images use a set of numbers to describe the intensity of a point of an image. As far as I recall the number is between 0 and 32767. That's not continuous. You can have 99 or 100 but not 99.5.
The blur you see on most analog systems if you increase the magnification is due to the finite wavelength of light and the finite size of the optical elements involved.
Tommya doesn't understand that the nerve signals from the eye to the brain are digital. (it's a form of pulse code modulation where the repetition frequency is related to the signal intensity.)
A nerve cell fires or it doesn't- that's a reasonable approximation to a digital signal in a camera.
Also, there are a finite number of rod and cone cells in the retina that receive the light. These correspond with the pixels in the camera.
There's another complication. the pixels in a camera are not just on or off, they carry intensity data as well. (That's why a 10 megapixel image file takes up much more than 10 megabits of storage space).
The information captured by a "digital" camera is, initially analog data and is digitised when it is read from the sensor.
In much the same way the eye produces analog data but it's encoded digitally.
Also, while it's true that the eye has some stupid design faults like having the blood supply in the way of the light, it's actually very good- the resolution is about a tenth of the diffraction limit. There's no way it could be as much as 10 times better.
Not only that but the quality of the optical system is a red herring, I can put a lousy lens on a digital camera- it's still digital.
I'm quite happy to look at (old fashioned) film.
The grains of silver halide are hit by light, if enough photons hit a grain then it is sensitised and forms part of the latent image. If you develop the file the grain turns from white silver halide to black metallic silver.
That's an all- or nothing response- you don't get half a grain to develop so the grains in a film can be thought of as equivalent to the pixels in the sensor of a digital camera.
The next thing to do is look at the number of grains you get.
Specialist films will resolve a thousand lines per millimetre (though they are very slow)
Typical negatives are about 20mm by 25mm so that's about 500 megapixels.
These pixels can't resolve any intensity data so the information carried is rather less than you would get from a 500 MP digital camera, but it's roughly equivalent to a digital image that takes up 500 megabits of data ie one that gives a 63Mbyte file.
It gets more complicated because most files get compressed before they are stored but I think that's still more data than any digital picture I have seen. More typical negatives with lower resolving power (like 100 lines / mm)would, of course, give fewer equivalent pixels
-
Not to mention that the human eye is not a very good optical system. Our brains seem to do an enormous amount of "post processing" of the actual image that's presented to the retina (which, of course, is also upside down!)
Thank ewe Mr Geezer very muchly. So not only do we receive piccys upside down but our brain really does all the seeing eh ?......AH !!..This reminds me of an experiment I saw where a chappy wore a device which presented the world he viewed upside down...it was only a matter of a short time before he could view the world with no problems as his brain corrected the situation......which is nice !..brains are great eh ?.....I think we should all be encouraged to acquire brains and use them.
-
You can't directly compare the quality of digital and analogue because there is no common framework of reference. It's a bit like comparing cats and custard!
.
In the human body, the sensors chemically blend together like a fluid and are not just a "hard", turn on, shut off process.
This is more an analog characteristic then a digital characteristic.
I think Tommy hit the nail on the head. Analogue images are particular, that is they are made out of discrete units. Whereas digital images use a continuous, non-divisable range of values. If you enlarge a digital image it becomes pixelated and granular whereas an analogue image becomes blurry and indistinct.
And Geezer's point that the majority of image perception is due to the processing power of the brain also makes it difficult to directly compare the eye with a digital camera.
[ Invalid Attachment ]
Custard Cat Approves John !
-
Hang on!
The eye is digital.
The human retina has about 70 million receptor cells so it's reasonable to say that it has the equivalent of about 70Mp
John has got this bit
"I think Tommy hit the nail on the head. Analogue images are particular, that is they are made out of discrete units. Whereas digital images use a continuous, non-divisable range of values. If you enlarge a digital image it becomes pixelated and granular whereas an analogue image becomes blurry and indistinct."
pretty much totally backwards.
Digital images are particular; the particles are called pixels.
Digital images use a set of numbers to describe the intensity of a point of an image. As far as I recall the number is between 0 and 32767. That's not continuous. You can have 99 or 100 but not 99.5.
The blur you see on most analog systems if you increase the magnification is due to the finite wavelength of light and the finite size of the optical elements involved.
Tommya doesn't understand that the nerve signals from the eye to the brain are digital. (it's a form of pulse code modulation where the repetition frequency is related to the signal intensity.)
A nerve cell fires or it doesn't- that's a reasonable approximation to a digital signal in a camera.
Also, there are a finite number of rod and cone cells in the retina that receive the light. These correspond with the pixels in the camera.
There's another complication. the pixels in a camera are not just on or off, they carry intensity data as well. (That's why a 10 megapixel image file takes up much more than 10 megabits of storage space).
The information captured by a "digital" camera is, initially analog data and is digitised when it is read from the sensor.
In much the same way the eye produces analog data but it's encoded digitally.
Also, while it's true that the eye has some stupid design faults like having the blood supply in the way of the light, it's actually very good- the resolution is about a tenth of the diffraction limit. There's no way it could be as much as 10 times better.
Not only that but the quality of the optical system is a red herring, I can put a lousy lens on a digital camera- it's still digital.
I'm quite happy to look at (old fashioned) film.
The grains of silver halide are hit by light, if enough photons hit a grain then it is sensitised and forms part of the latent image. If you develop the file the grain turns from white silver halide to black metallic silver.
That's an all- or nothing response- you don't get half a grain to develop so the grains in a film can be thought of as equivalent to the pixels in the sensor of a digital camera.
The next thing to do is look at the number of grains you get.
Specialist films will resolve a thousand lines per millimetre (though they are very slow)
Typical negatives are about 20mm by 25mm so that's about 500 megapixels.
These pixels can't resolve any intensity data so the information carried is rather less than you would get from a 500 MP digital camera, but it's roughly equivalent to a digital image that takes up 500 megabits of data ie one that gives a 63Mbyte file.
It gets more complicated because most files get compressed before they are stored but I think that's still more data than any digital picture I have seen. More typical negatives with lower resolving power (like 100 lines / mm)would, of course, give fewer equivalent pixels
Whoa !!
Thank ewe very much BC for your detailed specific comment which makes very interesting reading.
Gosh !...Intriguing !
It seems there are indeed direct correlations !
-
.
Series of Q & A precipitate more deductive reasoning.
Is this a suggestion? That digital utilizes a single set amplitude, with a series of iterations of square wave forms
Is what you explained, in the form of pulse code modulation?
The word "code", suggests a window of opportunity.
This suggests that there is no need for multiple routes, that data needs to travel.
Than, one solid nerve can do the job using this PCM. Remote controls use this idea so the only one frequency is needed.
Amplitude modulation on the other hand needs different routes to deliver information.
Lie detectors is sensitive to this amplitude intensity actions spike not just vibrate.
The heart is operates by the use of the nervous system!
If this pulse code modulation is a fact, "A fibrillation" symptoms would be considered a norm and not alarming.
Digital realm utilizes only ones and zeros on and off that is a scientific fact.
.
A nerve cell fires or it doesn't- that's a reasonable approximation to a digital signal in a camera.
Also, there are a finite number of rod and cone cells in the retina that receive the light. These correspond with the pixels in the camera.
There's another complication. the pixels in a camera are not just on or off, they carry intensity data as well. (That's why a 10 megapixel image file takes up much more than 10 megabits of storage space).
Someone definitely has the misconception of digital electronics, it is easy to do if you never worked with it..
Digital memory pointing
Every portion of memory is utilized (mapped), to a set of specific purposes. So does the human metabolism that where the similarities end.
Pixel positioning in the memory of the viewing screen is in a binary word form in single or double BCD words depending on the size of the pallet, resolution etc...
Next to that position in memory is the Attribute! A BCD set, giving that pixel its characteristics. These "words" are made from Ones and Zeros!
Thing of the memory for the screen is like a miniture size checker board or a pigeon shed.
Stuffed one hole with a pixel the next hole with an attribute, cascading depending of a given digital area of the screen, dictated by software and hardware physical limits.
This will give you an idea it shows the relationship of ones and zeros at its basics. A homemade digital abacus.
It does not show a full word.
The series of terms are at its basic; a bit, a byte, a nibble, a word... 32 bit word, 64 bit word, etc...
http://www.learn-c.com/data_lines.htm
Note: a blurred picture in digital is done by setting its adjacent pixels color's offset in a numerical cascade, gathered from an already set electronic pallet.
There is no intensity involved it is an illusion affect. Lighting is the same utilization of the set pallet.
.
-
Not to mention that the human eye is not a very good optical system. Our brains seem to do an enormous amount of "post processing" of the actual image that's presented to the retina (which, of course, is also upside down!)
Thank ewe Mr Geezer very muchly. So not only do we receive piccys upside down but our brain really does all the seeing eh ?......AH !!..This reminds me of an experiment I saw where a chappy wore a device which presented the world he viewed upside down...it was only a matter of a short time before he could view the world with no problems as his brain corrected the situation......which is nice !..brains are great eh ?.....I think we should all be encouraged to acquire brains and use them.
I am still waiting in the second line. The first time through I thought they said electric trains, I told them no thanks I have one already.
-
"Series of Q & A precipitate more deductive reasoning."
This isn't Q and A ; it's me telling you that you are wrong and need to find out how nerves work.
"The word "code", suggests a window of opportunity."
No it doesn't.
"Lie detectors is sensitive to this amplitude intensity actions spike not just vibrate."
Lie detectors look at the average of a large number of nerves. That average is more analog than digital.
"The heart is run by the nervous system, if this pulse code modulation is a fact, A fibrillation symptoms would be considered a norm and not alarming. "
Just plain wrong. Fibrilation is a problem. The nerves really do use pulse modulation. Since nerve impulses all have the same amplitude they are, in that regard, digital.
"Digital realm utilizes only ones and zeros on and off that is a scientific fact."
Good, at least you understand that.
Now you need to realise that nerves also use ones and zeros.
"Someone definitely has the misconception of digital electronics, it is easy to do if you never worked with it.."
Anybody reading this is working with digital electronics; the internet isn't analog.
For what it's worth I have worked with digital electronics since the late 70s
does this "Digital memory pointing Every portion of memory is utilized, to a set specific purposes. " actually mean anything, and if so, what?
I take it that the next bit is where you try to explain digital imaging. Well, I have seen it better explained elsewhere but the fact is that it doesn't matter.
You seem to sort of understand digital imaging but you don't seem to realise that the eye is very similar.
(Incidentally, in this case nybble has a different spelling.)
Anyway, the pixels in a camera are not just ones or zeros; they do include intensity data. If they didn't then a 10 MP image would only take up 1.25 MByte and it takes a lot more than that. I already pointed this out, but it seems you didn't understand it.
-
I am telling you that digital electronics is being misunderstood
I have produced references show me some please I want to learn more.
Nybble nibble either or...
http://en.wikipedia.org/wiki/Radio-controlled_helicopter
You need to show me reference your word here is not sound.
It is easy to dismiss thing you do not understand and what you wish.
I do remember a saying
If one can not find a way out a situation, look for a way in deeper.
-
I'm not sure if anyone pointed this out already, so apologies if this is redundant:
Another important difference between your average mark 1 eyeball and the digital camera, is that the camera actually produces a rather nice image of the view that the lens creates.
The human eye doesn't seem to do that. We perceive a sort of image in our brain, but if we hold our eyes on a single spot, most of the image is really poor. Only the object that we concentrate on has much definition at all. We make up for that of course by continuously moving our eyes to alter our objective.
So, in a way, what we "see" is probably a lot more like one of those really bad movies where the camera continuously pans and zooms. It's interesting that we have learned to handle this without actually puking all the time, although this may have something to do with motion sickness.
-
I'm not sure if anyone pointed this out already, so apologies if this is redundant:
Another important difference between your average mark 1 eyeball and the digital camera, is that the camera actually produces a rather nice image of the view that the lens creates.
The human eye doesn't seem to do that. We perceive a sort of image in our brain, but if we hold our eyes on a single spot, most of the image is really poor. Only the object that we concentrate on has much definition at all. We make up for that of course by continuously moving our eyes to alter our objective.
So, in a way, what we "see" is probably a lot more like one of those really bad movies where the camera continuously pans and zooms. It's interesting that we have learned to handle this without actually puking all the time, although this may have something to do with motion sickness.
Yea vertigo a theme to belch to
-
You need to show me reference your word here is not sound.
Do you know what ad hom means?
Anyway, here is some information about how nerves work which might be more relevant than something about toy helicopters.
http://en.wikipedia.org/wiki/Action_potential
-
You need to show me reference your word here is not sound.
Do you know what ad hom means?
Anyway, here is some information about how nerves work which might be more relevant than something about toy helicopters.
http://en.wikipedia.org/wiki/Action_potential
argument um ad homonym
I can see there is a bit of interesting things you do present
Still waiting on the nervous system with respect to that PCM reference.
Please I used deductive reasoning I could not find any reference to the original question
Now this is precipitating to non sense
-
This sounds like a vast compilation of useless information well worth not knowing. Thanks for information. Joe L. Ogan
-
"Still waiting on the nervous system"
Well, I did cite that wiki page; did you look into how the nervous system works?
Did you see this bit?
"
"All-or-none" principle
The amplitude of an action potential is independent of the amount of current that produced it. In other words, larger currents do not create larger action potentials. Therefore action potentials are said to be all-or-none (or boolean), since they either occur fully or they do not occur at all. Instead, the frequency of action potentials is what encodes for the intensity of a stimulus."
and do you understand it?
If this sort of thing
"Yea vertigo a theme to belch to"
"Now this is precipitating to non sense"
Is the best sort of response you can provide perhaps it would be better if you just gave up.
-
This sounds like a vast compilation of useless information well worth not knowing.
I'm glad we are able to maintain our usual standards.
-
I'm absolutely certain this question has been posed and answered on TNS forums before.
Anyhow, a major difference between the image sensor on a typical camera (CCD or CMOS) and the image-sensor in the eye (retina) is that the cameras have uniformly distributed and identical types of pixels over the whole image area -- whereas the retina has a cluster of high-resolution (but poorer sensitivity) colour sensors ("cones") in the central few degrees of vision (known as the fovea), and increasingly sparse and luminance-only (and much more low-light sensitivity) ("rods") in the periphery of vision.
The wonderful brain scans the eye around the image and builds up the detail and fills in (or makes up!) the blanks to make a complete perception of a scene.
So it doesn't make sense to ask what the total "megapixel" count of the human eye is, as you're not comparing like with like.
Also beware that camera-makers are full of sales-hype, and they count each R/G/B subpixel of the imager towards their 'megapixel' total - and then use digital upscaly filtering to deliver an image with that many complete RGB triplets (where we'd normally refer to an RGB triplet as a 'pixel'). In addition to limitations of the lenses, this contributes towards digital camera pictures not being as pixel-sharp as you might otherwise have naively hoped.
That said, the effective resolution of (the central part of the vision of) the eye equates to about 300dpi at a reading distance of about 14inches - if that helps. It comes from an angular resolution, so in millimetres will scale inversely with distance.
-
I'm absolutely certain this question has been posed and answered on TNS forums before.
I think you are absolutely right! At least once, but I didn't want to poke Neil in the eye [:D]
http://www.thenakedscientists.com/forum/index.php?topic=11174.0
-
John has got this bit
"Analogue images are particular, that is they are made out of discrete units. Whereas digital images use a continuous, non-divisable range of values. If you enlarge a digital image it becomes pixelated and granular whereas an analogue image becomes blurry and indistinct."
pretty much totally backwards.
Hi B.C. Yes, you are right, of course. I had it the right way round in my head and I'm not sure why it ended up written that way [;D].
Hang on! The eye is digital.
..... the nerve signals from the eye to the brain are digital. ...Also, there are a finite number of rod and cone cells in the retina that receive the light. These correspond with the pixels in the camera... [etc]
Well you've got me convinced. I have never thought about our vision as being a digital system before but your explaination make perfect sense to me.
-
I am beginning to taste the megacycles in my soup. Thanks for comments. Joe L. Ogan
-
I am beginning to taste the megacycles in my soup.
Joe: You have to use megahertz these days. It's something to do with the car rental outfit I think.
-
I'm absolutely certain this question has been posed and answered on TNS forums before.
I think you are absolutely right! At least once, but I didn't want to poke Neil in the eye [:D]
http://www.thenakedscientists.com/forum/index.php?topic=11174.0
DOH !!..well it was over two and half years ago !....plenty new peeps deserve to read the wondrous text that have been produced as a consequence of it's resurrection !
-
As I understand it, you may see a pixel but you have no pixels in your eye. Thanks for comments. Joe L. Ogan
-
Pixel just means picture element.
In the eye, the picture is made up from elements called rods and cones; the rods and cones are pixels.
-
I wonder how long before the ccd of digital cameras is designed with an 'artificial fovea' - by this I mean a concentration of cells/pixels in the centre. At present much of the ccd 'real estate' is wasted; a 6"x42 / 150mm x 100mm print has half its information in a 11/16" / 17.5mm band around the edge. Very few photographs have their subject matter in this area. A digital zoom to remove a small border, in fact loses half the information.
If the eventual limit on size of ccds is the file size (which I am not sure of at all) - then I would prefer that the centre of the photo is more information dense to allow for superior digital zooming. Matthew
-
Thank you for making me realize the nerves work in pulses, I was incorrect,
I do not know what PCM is used for. I do know that PCM contains more information in its waveform than just a modulated pulse. Thank you sincerely for correcting me in several areas you pointed out to me.
Here is something that interested me, I would like to share. It is over my head but it does sound like it isn't over yours.
"Computers operate on a single number that is essentially constant from each input pixel. (The computer pixel is basically the equivalent of a biological photoreceptor.) Fourth, the retina performs all these calculations in parallel while the computer operates on each pixel one at a time. There are no repeated summations and shifting as there would be in a computer. Finally, the horizontal and amacrine cells play a significant role in this process but that is not represented here."
I still stick to the idea that there are no pixels to be counted in the eye.
http://en.wikipedia.org/wiki/Retina
See ya
Later friend
NO Ad hominem abusive intended Sincerely
-
"I still stick to the idea that there are no pixels to be counted in the eye."
Please yourself, but there are about 100 million of them.
From the wiki page you cited
"Physical structure of human retina
In adult humans the entire retina is approximately 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods."
-
"I still stick to the idea that there are no pixels to be counted in the eye."
Please yourself, but there are about 100 million of them.
From the wiki page you cited
"Physical structure of human retina
In adult humans the entire retina is approximately 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods."
I believe BC is quite correct in saying that the cells on the retina constitute discrete light receptors. The CCDs in digital cameras are also discrete light receptors, so, at that level, there is little difference. It's interesting that the numbers are not so different either.
The camera's optics seems to be a bit better than human optics, but human post processing seems to be greatly superior to any digital camera currently available.
-
"I still stick to the idea that there are no pixels to be counted in the eye."
Please yourself, but there are about 100 million of them.
From the wiki page you cited
"Physical structure of human retina
In adult humans the entire retina is approximately 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods."
I believe BC is quite correct in saying that the cells on the retina constitute discrete light receptors. The CCDs in digital cameras are also discrete light receptors, so, at that level, there is little difference. It's interesting that the numbers are not so different either.
The camera's optics seems to be a bit better than human optics, but human post processing seems to be greatly superior to any digital camera currently available.
Yes I agree being put this way. I interpreted that site I had past on, shows the similarity and differences. My copied statement from that site.
Someone please interpret it please, because in different words in some parts I interperate it as coralation with
Techmind:
http://www.thenakedscientists.com/forum/index.php?topic=32278.msg313346#msg313346
The number of light receptors can be counted in the eye.
Pixels in a camera can be counted
If you decide to call the bio parts that similar in function with the particular computer part and label them as one label, us less educated people will never catch on.
-
If you decide to call the bio parts that similar in function with the particular computer part and label them as one label, us less educated people will never catch on.
I don't think there is any deception. The detectors in the eye and the detectors in a camera's CCD do the same thing. They both react to quanta of electromagnetic energy (aka photons) within a certain frequency range.
-
If you decide to call the bio parts that similar in function with the particular computer part and label them as one label, us less educated people will never catch on.
I don't think there is any deception. The detectors in the eye and the detectors in a camera's CCD do the same thing. They both react to quanta of electromagnetic energy (aka photons) within a certain frequency range.
OK I can understand that, but that was never contested not the issue...
can you please tell me this does not apply
"Computers operate on a single number that is essentially constant from each input pixel. (The computer pixel is basically the equivalent of a biological photoreceptor.) Fourth, the retina performs all these calculations in parallel while the computer operates on each pixel one at a time. There are no repeated summations and shifting as there would be in a computer. Finally, the horizontal and amacrine cells play a significant role in this process but that is not represented here."
-
It's ironic that one of the first stages of image processing in a camera is the conversion of an analog signal to a digital one. (The charge in each pixel is measured, then quantised).
In the eye, one of the first stages is the conversion of a digital signal to an analog one by summation in the retina.
However, it remains the case that both signals leave the eye or camera as digital ones- albeit processed. The optic nerves are either on and off, and so is the USB port signal (or whatever).
The actions of the retina are signal processing. when you look at a picture these processes happen whether the original picture is digital or analog. This post-procesing does not detract from the fact that the original image is captured by a finite array of individual pixels in both cases.
-
It's ironic that one of the first stages of image processing in a camera is the conversion of an analog signal to a digital one.
Perhaps not so ironic. It seems that "light" itself may be quantized in the form of photons. Photons seem to have rather digital characteristics.
BTW, I'm not claiming to understand much of this. These are just some of my sporadic thoughts.
-
Something which has been hinted at so far, but I thought I would say explicitly:
One big difference is that a camera has a constant pixel density all over the image, where as your eye has a very high pixel density at the fovea and a much lower one everywhere else. So you see 'what you are looking at' at a much higher resolution (and in better colour) than everything else.
This actually makes the job of making a camera more difficult as when looking at a photo you can move your eyes around, so if the camera tried the same trick as your eyes, you would complain that the edges of the photo looked pixelated or at least out of focus. So the camera manufacturers need to pump out high resolution everywhere with a consequent increase in data that they have to throw around.