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"Red Eye" effect of animals
I am writing an article about "red eye" effect of people and animals.
What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? Natalia |
wrote:
I am writing an article about "red eye" effect of people and animals. What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? It depends on the animal. A lot of late evening or night time predators have a special reflective layer at the back of their retina that give the photoreceptors almost twice the sensitivity of a human eye. Hence you don't see red eye from blood vessels so much as bluish eye from the reflective layer. The exact colour is very angle dependent. Regards, Martin Brown |
wrote:
I am writing an article about "red eye" effect of people and animals. What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? Natalia Dogs and cats seem to have a lot more rods than cones in their retinas, and the angle from which the light reflects seems to vary the color, even though the rods aren't color sensitive. Fixing this problem in post-processing is much like doing the same with human eyes, except that many programs look for the red tones, which are usually absent in animal eyes (excpet other primates). -- Ron Hunter |
wrote:
I am writing an article about "red eye" effect of people and animals. What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? Natalia To oversimplify this a little, what is happening is the light from your flash is reflecting off the back of the eye. Since the eyes are seldom at the same angle, you often get different reflections. Different animals (we are animals after all) have differences in the construction of their eyes so the results tend to vary. Cats and other night animals tend to have a totally different kind of iris designed for night vision so they tend to display more of the effect. Moving the main light source away from the camera tends to reduce the problem since the reflections is less likely to be reflected back at the camera. -- Joseph Meehan 26 + 6 = 1 It's Irish Math |
On Thu, 03 Mar 2005 10:24:29 +0000, Martin Brown
wrote: wrote: I am writing an article about "red eye" effect of people and animals. What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? It depends on the animal. A lot of late evening or night time predators have a special reflective layer at the back of their retina that give the photoreceptors almost twice the sensitivity of a human eye. Hence you don't see red eye from blood vessels so much as bluish eye from the reflective layer. The exact colour is very angle dependent. Regards, Martin Brown Martin Brown, you wrote "A lot of late evening or night time predators have a special reflective layer at the back of their retina that give the photoreceptors almost twice the sensitivity of a human eye." Thus this may well be the next major evolution to come along & advance digital camera sensors. Picture a CMOS or CCD or other type of sensor with a similar reflective coating thus providing nearly twice the light sensitivity per unit of time/area. This may not happen for a while because the brain has to perform rather complex processing of the reflected light. So even a tiny field mouse has many times the processing power of the fastest digital camera image processor. Rather humbling when you look at how far Mother mature is ahead of us, but then again Mother nature has been working at it a lot longer than we have. LOL If you think this process would not work, I invite you to check out how a LED (Light Emitting Diode) works to produce narrow band light. This process is reversible, I often use different color LEDs as sensors to "detect" light. A "white" LED is actually the best example of the principle working in reverse. Just thinking out loud as an E. T. Electronic Technician, not Extra Terrestrial. Come to think of it, some of my friends & colleagues are still waiting for me to call home! LOL! Respectfully, DHB "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 |
On Thu, 03 Mar 2005 14:48:43 GMT, DHB wrote:
On Thu, 03 Mar 2005 10:24:29 +0000, Martin Brown wrote: "A lot of late evening or night time predators have a special reflective layer at the back of their retina that give the photoreceptors almost twice the sensitivity of a human eye." Thus this may well be the next major evolution to come along & advance digital camera sensors. Picture a CMOS or CCD or other type of sensor with a similar reflective coating thus providing nearly twice the light sensitivity per unit of time/area. This may not happen for a while because the brain has to perform rather complex processing of the reflected light. So even a tiny field mouse has many times the processing power of the fastest digital camera image processor. Rather humbling when you look at how far Mother mature is ahead of us, but then again Mother nature has been working at it a lot longer than we have. LOL If you think this process would not work, I invite you to check out how a LED (Light Emitting Diode) works to produce narrow band light. This process is reversible, I often use different color LEDs as sensors to "detect" light. A "white" LED is actually the best example of the principle working in reverse. So, if you can just bundle 6 million of these leds together in a flat panel (approx) 9m by 6m, you've got yourself a camera. Now, for the lens... Kidding aside, I have a BSc in Digital Electronics and was wondering how the LEDs are used as sensors - you seem to imply that a red LED can detect red light - is this primarily because it has a red filter, (ie a clear-case red LED can't do this?), and what's so special about the white LEDs in this respect? -- Owamanga! |
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On Thu, 03 Mar 2005 16:50:59 GMT, Owamanga wrote:
So, if you can just bundle 6 million of these leds together in a flat panel (approx) 9m by 6m, you've got yourself a camera. Now, for the lens... Kidding aside, I have a BSc in Digital Electronics and was wondering how the LEDs are used as sensors - you seem to imply that a red LED can detect red light - is this primarily because it has a red filter, (ie a clear-case red LED can't do this?), and what's so special about the white LEDs in this respect? Owamanga, well I'm an ET, retired at that, not an EE but I will do my best to explain it mostly from memory. No it's not the lens color that determines the LED's light output color, it's composition does that. 1st it might be helpful to state that "all" PN junctions (diodes) emit photons when forward biased & the effect is reversible. This is why we have "photo diodes & photo transistors". LED are simply build to maximize this effect & the are doped with specific impurities or made from different materials to alter the wavelength from the usual UV to something usually within the human visual spectrum. Red LEDs depending on the frequency & efficiency may be GaAsP, IR (actually should be called NIR Near InfaRed) use AiGaAs or AaAsSi. The same individual that invented the blue LED also invented the 1st practical white LED that we use today. One of the 1st attempts to create a white LED used 3 LEDs in 1 housing which produce what the human eye perceived as some white but it also could see the 3 primary colors used, especially if you did not look directly at it. How was this problem solved? Fire a blue LED onto a Yellow phosphor & the human eye see's what it believes is white. Don't ask me to explain this, it's outside of my field. Have you ever seen those white LED night lights? I have a few & have taken digital pictures with 1 in the background & my camera recorded it as a very light blue light. The reason I specified a white LED is because the phosphor acts a bit like a reflective surface of a nocturnal critter's eye. Sorry about this being a bit off topic but I only intended to indicated that it may be possible for this same principle to be adapted to a digital camera's sensor to increase it's sensitivity to light. Also, I did state "or other type of sensor" because it may not be compatible with either CMOS or CCD. And using an LED as a photo diode is not very efficient but it's extremely inexpensive & works just fine for many applications & does not require a narrow band optical or electronic filter because it's response varies from only about 30-150 nanometers. Also it's peak sensitivity is the same as it's peak color output if used as an LED to "emit" light rather than "detect" it. Most motors also work as poor quality generators, even the motors running in your PC that keep it cool will produce a small voltage when wind blows through it & spins it. A poor man's high wind detector! Respectfully, DHB "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 |
In article , says...
wrote: I am writing an article about "red eye" effect of people and animals. What I noticed is when you take a photo of the same animal, its eyes can have different colors on different photos or even its left and right eyes has different colors on the same photo. I think this depends on the angle at which you take a photo, rather than on tapetal color. Am I right? I never heard of it before, so it is just my assumption... Please see the photos of the animals: http://www.colorpilot.com/redeye_effect01.html all 6 pictures of a dog show actually the same dog... What do you think? Natalia Dogs and cats seem to have a lot more rods than cones in their retinas, and the angle from which the light reflects seems to vary the color, even though the rods aren't color sensitive. Fixing this problem in post-processing is much like doing the same with human eyes, except that many programs look for the red tones, which are usually absent in animal eyes (excpet other primates). The only real fix for this is to move the flash OFF CAMERA, and not get the red-eye to begin with. I purchased a handle/bracket (mounts on the tripod mount of the camera) at Ritz Camera for $14 (US) that has a shoe for the flash. If your camera has a pc cable connector you can put a flash on the handle and move the center of the flash as much as 10 inches from the camera lens. This works MUCH better all around (for people and animals). If your camera doesnt have a PC connector for the flash you can put the flash on aa "autotrip" module (another $10 (US) at Ritz) then put a piece of foil or plastic over the on camera flash to reflect the flash toward the off camera flash instead of the subject. All of this only works in MANUAL without pre-flash or red-eye reduction turned on. -- Larry Lynch Mystic, Ct. |
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