Re: [pinhole-discussion] Human eye
Ellis, Actually you are slightly wrong. For colours the official vision angle is 10 deg. If interested in details, look here: http://colour.derby.ac.uk/colour/info/glossary/c/CIE1964Observer.html taco Sorry to be pedantic, I am not wrong, the source I got it from would be ( but I did not make a note of it !). However, I note that the site in your message referred to 'ideal viewer', I am interested in actual average view, which is good enough for me. Thank you for your interest. Ellis ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Human eye
ellis CORY wrote: It was good of Gary to resurrect my old question, times have moved on from then and I have gained a lot of useful information. After all, 'meaningless' is in the eye of the beholder ! and for the purposes I required, eveything I have found out is 'meaningful. For those interested AVERAGE values are: Cornea to retina 24mm Lens dia. 9mm Light sensitive Rods (black and white) 400+ASA High light sensitivity, low resolution Cones (colour) 25 ASA Low light sensitivity, high resolution Normally sensitive to yellow/green light during the day blue/green at night. Acute vision angle 15 deg. Ellis, Actually you are slightly wrong. For colours the official vision angle is 10 deg. If interested in details, look here: http://colour.derby.ac.uk/colour/info/glossary/c/CIE1964Observer.html taco
Re: [pinhole-discussion] Human eye
It was good of Gary to resurrect my old question, times have moved on from then and I have gained a lot of useful information. After all, 'meaningless' is in the eye of the beholder ! and for the purposes I required, eveything I have found out is 'meaningful. For those interested AVERAGE values are: Cornea to retina 24mm Lens dia. 9mm Light sensitive Rods (black and white) 400+ASA High light sensitivity, low resolution Cones (colour) 25 ASA Low light sensitivity, high resolution Normally sensitive to yellow/green light during the day blue/green at night. Acute vision angle 15 deg. Data from up to 200 deg. Attentive angle 20-30 deg. Angle of view 46 deg Iris dia 2mm bright light, 8mm dim light Focal length 80 - 120 mm Distant focus 6m - infinity Focus range 25 cm - infinity Persistance of vision (shutter speed?) 0.1 s From: Gary Nored On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis This question comes up from time to time in a number of photo-related groups. The best answer is that it is a meaningless question. The human visual system does so much post processing that what we see, and how well, bears no resemblance to the optical performance of the eyeball itself. Our visual experience is essentially wide field (vertically and horizontally), ultra high-definition, full color, moving, with infinite depth of field in almost any lighting situation. If you were looking only at the eye's performance you would get the idea that human vision is characterized by poor resolution in only a very narrow field, surrounded by terrible resolution over the wide field. The depth of field would appear to be poor in all but full sunlight and there is a blind spot in the picture! The thing I like most about pinhole photography is that the process prevents the brain from processing everything into a realistic image, which gives us a whole new visual perspective of the world. Gary Nored
Re: [pinhole-discussion] Human eye
On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis This question comes up from time to time in a number of photo-related groups. The best answer is that it is a meaningless question. The human visual system does so much post processing that what we see, and how well, bears no resemblance to the optical performance of the eyeball itself. Our visual experience is essentially wide field (vertically and horizontally), ultra high-definition, full color, moving, with infinite depth of field in almost any lighting situation. If you were looking only at the eye's performance you would get the idea that human vision is characterized by poor resolution in only a very narrow field, surrounded by terrible resolution over the wide field. The depth of field would appear to be poor in all but full sunlight and there is a blind spot in the picture! The thing I like most about pinhole photography is that the process prevents the brain from processing everything into a realistic image, which gives us a whole new visual perspective of the world. Gary Nored
Re: [pinhole-discussion] Human eye
Ahh, thanks for the explanation. g Cheers - george (knuckle dragger) --- Alan Cangemi ac-t...@msn.com wrote: Ahhh, George, Now I see the confusion. The old style brains (those used before 1985) did in fact see lights as individual frames. But the modern brain, especially those in people born after 1986, see light as a continuous stream. Even though the old style brains are still manufactured and used (mostly for economic reasons.the new styled brains cost 4 times as much) most people nowadays are using the new brains. It's easy to spot those with new and old styled brains.the old style recipients tend to drag their knuckles when they walk upright. Sorry for the confusion, George. Best regards. Alan (old style) Cangemi - Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Monday, January 06, 2003 8:56 PM Subject: Re: [pinhole-discussion] Human eye Well, you'll need to speak with my Physiological Psychology teacher of 30 years ago, as that is what our textbook said. We do not see things as continuous streams, but as frames. Cheers - george --- Alan Cangemi ac-t...@msn.com wrote: George. The brain DOES NOT take in light similar to a movie camera's film mechanism. It sees light as a continuous stream. It is only through mechanical processes that wheels appear to be turning backwards whilst the vehicle is moving forward. So there! sreehC Alan - Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Monday, January 06, 2003 5:53 PM Subject: Re: [pinhole-discussion] Human eye While light does stream in continuously, the brain takes it in similar to a movie camera's film. This is why you may see a bicycle's tires appear to move backwards as it goes forwards. Cheers - george --- erick...@hickorytech.net wrote: Another thing occurs to me. The camera analogy is also limited by the fact that camera shutters open and close, while light streams into the human eye continuously. The operative 'shutter speed would have to be the duration of exposure to the rod or cone required to trigger nerve conduction. I don't know whether there is a trasmission period followed by a refractory period, which would equate to shutter speed, or not. - Original Message - From: erick...@hickorytech.net To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 11:30 AM Subject: Re: [pinhole-discussion] Human eye Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking
Re: [pinhole-discussion] Human eye
Ahhh, George, Now I see the confusion. The old style brains (those used before 1985) did in fact see lights as individual frames. But the modern brain, especially those in people born after 1986, see light as a continuous stream. Even though the old style brains are still manufactured and used (mostly for economic reasons.the new styled brains cost 4 times as much) most people nowadays are using the new brains. It's easy to spot those with new and old styled brains.the old style recipients tend to drag their knuckles when they walk upright. Sorry for the confusion, George. Best regards. Alan (old style) Cangemi - Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Monday, January 06, 2003 8:56 PM Subject: Re: [pinhole-discussion] Human eye Well, you'll need to speak with my Physiological Psychology teacher of 30 years ago, as that is what our textbook said. We do not see things as continuous streams, but as frames. Cheers - george --- Alan Cangemi ac-t...@msn.com wrote: George. The brain DOES NOT take in light similar to a movie camera's film mechanism. It sees light as a continuous stream. It is only through mechanical processes that wheels appear to be turning backwards whilst the vehicle is moving forward. So there! sreehC Alan - Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Monday, January 06, 2003 5:53 PM Subject: Re: [pinhole-discussion] Human eye While light does stream in continuously, the brain takes it in similar to a movie camera's film. This is why you may see a bicycle's tires appear to move backwards as it goes forwards. Cheers - george --- erick...@hickorytech.net wrote: Another thing occurs to me. The camera analogy is also limited by the fact that camera shutters open and close, while light streams into the human eye continuously. The operative 'shutter speed would have to be the duration of exposure to the rod or cone required to trigger nerve conduction. I don't know whether there is a trasmission period followed by a refractory period, which would equate to shutter speed, or not. - Original Message - From: erick...@hickorytech.net To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 11:30 AM Subject: Re: [pinhole-discussion] Human eye Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When
Re: [pinhole-discussion] Human eye
Well, you'll need to speak with my Physiological Psychology teacher of 30 years ago, as that is what our textbook said. We do not see things as continuous streams, but as frames. Cheers - george --- Alan Cangemi ac-t...@msn.com wrote: George. The brain DOES NOT take in light similar to a movie camera's film mechanism. It sees light as a continuous stream. It is only through mechanical processes that wheels appear to be turning backwards whilst the vehicle is moving forward. So there! sreehC Alan - Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Monday, January 06, 2003 5:53 PM Subject: Re: [pinhole-discussion] Human eye While light does stream in continuously, the brain takes it in similar to a movie camera's film. This is why you may see a bicycle's tires appear to move backwards as it goes forwards. Cheers - george --- erick...@hickorytech.net wrote: Another thing occurs to me. The camera analogy is also limited by the fact that camera shutters open and close, while light streams into the human eye continuously. The operative 'shutter speed would have to be the duration of exposure to the rod or cone required to trigger nerve conduction. I don't know whether there is a trasmission period followed by a refractory period, which would equate to shutter speed, or not. - Original Message - From: erick...@hickorytech.net To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 11:30 AM Subject: Re: [pinhole-discussion] Human eye Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account
Re: [pinhole-discussion] Human eye
While light does stream in continuously, the brain takes it in similar to a movie camera's film. This is why you may see a bicycle's tires appear to move backwards as it goes forwards. Cheers - george --- erick...@hickorytech.net wrote: Another thing occurs to me. The camera analogy is also limited by the fact that camera shutters open and close, while light streams into the human eye continuously. The operative 'shutter speed would have to be the duration of exposure to the rod or cone required to trigger nerve conduction. I don't know whether there is a trasmission period followed by a refractory period, which would equate to shutter speed, or not. - Original Message - From: erick...@hickorytech.net To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 11:30 AM Subject: Re: [pinhole-discussion] Human eye Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com
Re: [pinhole-discussion] Human eye
Hi all, Here's my bit on the eye/camera subject: Different parts of the visual field are processed by the brain at different speeds, if you notice a TV or a computer monitor in the edge of your field of vision then you can often see the flicker of the scanning beam down the screen (depends on refresh rates with some monitors) and the more attention you pay to it the less it will flicker as your brain increases the processing it dedicates to that part of you vision. You don't see this if you look directly at the screen. This is probably because the density of information to be processed originating from the centre of the retina is far greater than at the periphery, colour, for example is mostly from the middle and our resolving power is greater in the middle because of the massive density of cones and rods (the light sensitive cells) that there are in the centre. I'd say that the analogies between the eye and a camera pretty much stop (no pun intended) at the level of the eye (not including the retina, as that is actually part of the brain) that is to say there is a two stage focusing device (cornea and lens) with an aperture that projects an image onto a light sensitive device (retina) however, that is where the analogies stop because one cannot really compare the retina and film. The digital analogy is better but there would have to be about 20-100? parallel supercomputers running full whack to process the amount of data that the retina continually produces to project a continually changing and real-time attentionally modulated visual scene that approaches the quality achieved by our higher brain visual centres effortlessly. Then consider the time and energy/power consumed and heat produced by these computers, when all any of us needs is a drink of water and a bowl of rice and peas a few times a day, of course we have to off-line for 1/3rd of every day but I digress Sorry for the essay, neuroscience is my other passion. Tom
Re: [pinhole-discussion] Human eye
Not quite. In the early days of motion pictures there were no standards. Since both the camera and projector were hand cranked, each film had it's own projection speed. To save on film costs, many early movies were shot and projected as slow as 20 frames per second (and sometimes even slower...) leading to the Brittish slang term for movies: flickers. Eventually, the projection speed was standardized at 24 frames per second -- this is still the standard today. 24 fps was chosen because that is the speed at which a projected image does not seem to flicker. 30 frames per second is the frame rate of television in North America, but that rate has little to do with the physiology of vision, and more to do with practical electronics (hint: the frequency of house current in N. Amer. is 60 herz). Mike Vande Bunt Steve Bell wrote: a little fact that may help: when motion pictures/films were first being made, they were projected at one frame every 30th of a second. this was the slowest the pictures could move without the human eye detecting that it wasn't one, but many frames. so my conclusion is that the slowest 'shutter speed' of the human eye is 1/30 sec. i'm sure that we have faster 'speeds' built in there somewhere. cheers, Steve [Original Message] From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Date: 1/5/2003 11:53:02 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ --- Steve Bell --- veracity...@earthlink.net --- We have...become our own thought police; but instead of calling the process by which we limit our own expression of dissent and wonder 'censorship', we call it 'concern for commercial viability'. -David Mamet ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Human eye
Steve Bell wrote: a little fact that may help: when motion pictures/films were first being made, they were projected at one frame every 30th of a second. this was the slowest the pictures could move without the human eye detecting that it wasn't one, but many frames. so my conclusion is that the slowest 'shutter speed' of the human eye is 1/30 sec. i'm sure that we have faster 'speeds' built in there somewhere. I'm fairly sure that currently 35mm motion pictures are shot at 24 frames per second. And either 8mm or Super8 is shot at 18 frames per second. If I recall correctly film shot at 24fps is projected in such a way that each frame is shown twice at effectively 48fps. NTSC video is about 30 frames per second, and each frame is two fields (60 fields per second). PAL video is 25 frames per second. I don't know if PAL uses fields. There have been other (faster) frame rates used by various systems, but they tend to lose out to the double whamy of needing special projectors and using more film. -- Brian Reynolds | But in the new approach, as you know, reyno...@panix.com | the important thing is to understand http://www.panix.com/~reynolds/ | what you're doing rather than to get | the right answer. -- Tom Lehrer
Re: [pinhole-discussion] Human eye
George I don't often have anything new or original to contribute to the discussion (and after this post the consensus will probably be 'just as well') but I can confirm that pinpoint pupils (eg from narcotic analgesia) are commonly about one millimetre in diameter, average pupil size is 2-3 mm (indoor lighting) but I have only seen 8mm pupils (fixed dilated) in the deceased. Ray
Re: [pinhole-discussion] Human eye
Another thing occurs to me. The camera analogy is also limited by the fact that camera shutters open and close, while light streams into the human eye continuously. The operative 'shutter speed would have to be the duration of exposure to the rod or cone required to trigger nerve conduction. I don't know whether there is a trasmission period followed by a refractory period, which would equate to shutter speed, or not. - Original Message - From: erick...@hickorytech.net To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 11:30 AM Subject: Re: [pinhole-discussion] Human eye Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Human eye
Here is some information I have. How it applies I'm not sure. The eye is only the aperture, lens and sensing apparatus. Because the eye is attached to the brain it would make more sense to use a digital camera as a model rather than film camera. The mind can read an image and give a response in as little as 0.04 seconds- a professional pingpong players response time, for instance. Nerve transmission time mind to brain can be measured by measuring cortical evoked potential responses to visual stimuli. I might have once know the limiting values but I don't recall them. A big name in research in this area is Meichenbaum, if you want to look it up. As for aperture, the lens to retina distance is roughly 25 mm. Maximum pupil size, i.e. aperture diameter, is maybe 8 mm in an adult, so the maximum F stop would be 25/8= 3.1. Minimum aperture would be about 25/2 for 'pinpoint pupils, an F stop of 12.5. I think that the eye processes light sensation somewhat differently at low light levels, so film speed would be a guess. Remember too that the eye and brain cannot distinguish as separate images any sequence more rapid than about 14/second. That is the basis for movies and television, sequences of still images projected faster than the eye can distinguish, thus blending them into apparent continuous motion. I- Original Message - From: George L Smyth glsm...@yahoo.com To: pinhole-discussion@p at ??? Sent: Sunday, January 05, 2003 10:53 AM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Human eye
On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis When I looked into shutter speed many years ago, I came upon the conclusion that the eye's shutter speed is approximately 1/100 second. You can verify this by taking successive pictures of a waterfall. We all know that slowing down the shutter speed to a second or more will make for silky water, which is not what we see. From there, take pictures with faster and faster speeds (don't forget to take notes). When you get the results, compare the pictures with what you see and make the decision for yourself. Cheers - george = Handmade Photographic Images - http://GLSmyth.com DRiP Investing - http://DRiPInvesting.org __ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com
Re: [pinhole-discussion] Human eye
If the human eye/mind could be translated to camera variables.. then wouldn't it be sad to be laying on ones death bed, and start to reflect on the life we lived only to find out we forgot to put film in our camera/head. think about it. - Original Message - From: Gary Nored gno...@centurytel.net To: pinhole-discussion@p at ??? Sent: Saturday, January 04, 2003 11:19 PM Subject: Re: [pinhole-discussion] Human eye On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis Difficult to answer this one (though some will try) because the human brain does so much post processing. Neasurements of eyeball parameters such as resolution or depth of field are largely meaningless; that is, we see much better than eyeball specifications would indicate. For example, no matter what the eyeball's depth of field, we perceive our 'depth of field' to be infinite because that which we attend is always in focus, and the brain fills in the rest to make it seem so. Our 'focal range' changes with age. Young people can see as close as a few centimeters -- older folks may struggle with a meter or more. Our 'film speed' is continuously variable -- a dark adapted eye can detect just a few photons yet we can also operate well on a sunny day at the beach -- this is far more change than can be accommodated by changes in our 'f-stop setting' (iris diameter). Even our 'shutter speeds' can seem extremely short because for the most part we see even fast-moving objects clearly and unblurred thanks to the image processing our brains do. Regards, Gary Nored ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Human eye
On 22 Jul 2002, at 11:16, eco...@aol.com wrote: I know this is not strictly pinhole, but I wondered if anyone had access to the average human eye values for the camera variables. ie Respective - film speed, shutter speed, aperture, focus range, depth of field etc. Thanks Ellis Difficult to answer this one (though some will try) because the human brain does so much post processing. Neasurements of eyeball parameters such as resolution or depth of field are largely meaningless; that is, we see much better than eyeball specifications would indicate. For example, no matter what the eyeball's depth of field, we perceive our 'depth of field' to be infinite because that which we attend is always in focus, and the brain fills in the rest to make it seem so. Our 'focal range' changes with age. Young people can see as close as a few centimeters -- older folks may struggle with a meter or more. Our 'film speed' is continuously variable -- a dark adapted eye can detect just a few photons yet we can also operate well on a sunny day at the beach -- this is far more change than can be accommodated by changes in our 'f-stop setting' (iris diameter). Even our 'shutter speeds' can seem extremely short because for the most part we see even fast-moving objects clearly and unblurred thanks to the image processing our brains do. Regards, Gary Nored
