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What If Your Eyes Were Cameras?
by Keenan Hursh
The human eye is a truly remarkable product of evolution. In combination with our brains, they are taking in massive amounts of information every second of every day and are one of the main sensory organs we use to navigate throughout our lives.
Perhaps we don’t have the most impressive eyes compared to other animals such as the mantis shrimp or raptors like eagles and owls, but none the less our eyes are incredibly versatile and adaptable optical devices with crystal clear lenses (our corneas), high-resolution sensors (our retinas), and incredibly intelligent, fast, and advanced processors (our brains).
Ever since I started taking photos, I’ve wondered why the pictures I take sometimes appear quite different from what I’m seeing with my eyes. I’ve always wondered if there is a camera setup out there that perfectly recreates human vision. And, if our eyes theoretically were cameras, what would the technical specs be?
Perhaps we don’t have the most impressive eyes compared to other animals such as the mantis shrimp or raptors like eagles and owls, but none the less our eyes are incredibly versatile and adaptable optical devices with crystal clear lenses (our corneas), high-resolution sensors (our retinas), and incredibly intelligent, fast, and advanced processors (our brains).
Ever since I started taking photos, I’ve wondered why the pictures I take sometimes appear quite different from what I’m seeing with my eyes. I’ve always wondered if there is a camera setup out there that perfectly recreates human vision. And, if our eyes theoretically were cameras, what would the technical specs be?
I’ll start out by saying that this is a question that has been asked many times before and in doing my research I’ve concluded that, in many ways, it is very difficult to compare the human eye to any camera. These are both complex systems that absorb light and create images but how they execute this task are quite different and often difficult to compare.
For instance, our brains aren’t creating a rectangular 2D collection of pixels like a camera sensor, instead, we’re creating incredibly complex 3D scenes in our minds. Our brains construct images based on key information our eyes focus on like faces, prominent colors and textures, and moving objects. These images temporarily live in our minds for a maximum of 15 seconds before they are replaced with newer information as opposed to a camera that can freeze a moment forever as a digital image.
In addition, a sensor is a flat rectangular plane whereas our retinas, which house a collection of light-sensitive photoreceptors called rods and cones, are curved parabolic planes. This is why you have a primary or central field of view in your vision where objects in the center of your field of view are much more in focus and sharp as opposed to objects in your peripheral vision.
So yes, it’s difficult to compare apples to oranges, but at the end of the day our eyes do indeed function in much the same way as a modern video camera and therefore I can attempt to give a rundown on the technical specifications of the human eye.
So let’s get into it. Here are the camera specs of the human eye.
For instance, our brains aren’t creating a rectangular 2D collection of pixels like a camera sensor, instead, we’re creating incredibly complex 3D scenes in our minds. Our brains construct images based on key information our eyes focus on like faces, prominent colors and textures, and moving objects. These images temporarily live in our minds for a maximum of 15 seconds before they are replaced with newer information as opposed to a camera that can freeze a moment forever as a digital image.
In addition, a sensor is a flat rectangular plane whereas our retinas, which house a collection of light-sensitive photoreceptors called rods and cones, are curved parabolic planes. This is why you have a primary or central field of view in your vision where objects in the center of your field of view are much more in focus and sharp as opposed to objects in your peripheral vision.
So yes, it’s difficult to compare apples to oranges, but at the end of the day our eyes do indeed function in much the same way as a modern video camera and therefore I can attempt to give a rundown on the technical specifications of the human eye.
So let’s get into it. Here are the camera specs of the human eye.
Field of View/Focal Length
Let’s start with the human eye’s field of view and focal length. Technically, the focal length of any lens is the distance between the optical center of the lens and the sensor. In this case, the focal length of the human eye is anywhere from about 17-24mm, but this isn’t the whole story.
Many of us have probably heard of “normal” lenses which are said to accurately replicate human vision. These are often 35 or 50mm lenses and are really just rough estimations based on what our eyes primarily focus on.
As I mentioned before our retinas, the surface an image is projected on at the back of our eyeballs, are curved, unlike a flat camera sensor. Because of this, our vision gets less sharp as we move away from the center of the retina where the projection of light is the sharpest. This “high resolution” section of your retina is called your fovea, the region in the center of your retina which has a higher concentration of rods and cones.
Technically our field of view is about 120-200 degrees and there’s also a roughly 130-degree overlap between what our left and right eyes are seeing. A super wide-angle field of view like this is comparable to a very wide-angle lens like a 5-6mm fisheye and technically we do see this entire scene but our central field of view, where all the action happens, is only about 40-60 degrees. If you take the average of our central field of view, roughly 50-55 degrees, you arrive at a 43mm lens. Because of this, I don’t think a super wide-angle fisheye lens is the most comparable to the way we see the world.
So, we’ve arrived at several different focal lengths depending on how you look at it. If we’re looking at our entire field of view a focal length of 5mm sounds right. If we’re just focusing on our central field of view a 43-50mm lens sounds right. Perhaps there’s no exact answer but when looking at the entire range those “normal” lenses that have been around for a while don’t seem too far off.
Let’s start with the human eye’s field of view and focal length. Technically, the focal length of any lens is the distance between the optical center of the lens and the sensor. In this case, the focal length of the human eye is anywhere from about 17-24mm, but this isn’t the whole story.
Many of us have probably heard of “normal” lenses which are said to accurately replicate human vision. These are often 35 or 50mm lenses and are really just rough estimations based on what our eyes primarily focus on.
As I mentioned before our retinas, the surface an image is projected on at the back of our eyeballs, are curved, unlike a flat camera sensor. Because of this, our vision gets less sharp as we move away from the center of the retina where the projection of light is the sharpest. This “high resolution” section of your retina is called your fovea, the region in the center of your retina which has a higher concentration of rods and cones.
Technically our field of view is about 120-200 degrees and there’s also a roughly 130-degree overlap between what our left and right eyes are seeing. A super wide-angle field of view like this is comparable to a very wide-angle lens like a 5-6mm fisheye and technically we do see this entire scene but our central field of view, where all the action happens, is only about 40-60 degrees. If you take the average of our central field of view, roughly 50-55 degrees, you arrive at a 43mm lens. Because of this, I don’t think a super wide-angle fisheye lens is the most comparable to the way we see the world.
So, we’ve arrived at several different focal lengths depending on how you look at it. If we’re looking at our entire field of view a focal length of 5mm sounds right. If we’re just focusing on our central field of view a 43-50mm lens sounds right. Perhaps there’s no exact answer but when looking at the entire range those “normal” lenses that have been around for a while don’t seem too far off.
Aperture/F-Stop
In photography, f-stop refers to how much light is entering your lens and how bright your exposure is. It’s really a calculation of the ratio between your lens’s focal length and aperture diameter. So, a 400mm lens with a maximum aperture diameter of 100mm has an f-stop of f/4. The human eye has a focal length of about 17-24mm and a maximum pupil diameter of about 8mm. Using these numbers, we can calculate that the human eye has an f-stop of about f/2.1-f/3.8. Which is very comparable to many camera lenses on the market today.
In photography, f-stop refers to how much light is entering your lens and how bright your exposure is. It’s really a calculation of the ratio between your lens’s focal length and aperture diameter. So, a 400mm lens with a maximum aperture diameter of 100mm has an f-stop of f/4. The human eye has a focal length of about 17-24mm and a maximum pupil diameter of about 8mm. Using these numbers, we can calculate that the human eye has an f-stop of about f/2.1-f/3.8. Which is very comparable to many camera lenses on the market today.
Resolution/Detail
The resolution or detail of the human eye is another specification that is difficult to calculate due to our curved retinas and the way our brains interpret the images our eyes create. 20/20 vision for instance only applies to our central field of view. Outside of this, we can’t really interpret fine details. In fact, it’s estimated that just 20 degrees off the center of our field of view we can only interpret 1/10th the amount of detail.
And, as mentioned before. The final image in our brains isn’t a quantifiable number of pixels on a sensor. Instead, it’s a 3D interpretation of what our eyes are seeing. So how can we calculate the resolution of the human eye? Well, we can compare our eyes to cameras of different resolutions and measure how well they can detect fine details. And many people have done this. If we just take our sharp, central field of view and don’t take into account our peripheral vision then our eyes roughly equate to a 15-megapixel sensor. If we apply this resolution to our entire field of view, then we arrive at a sensor of roughly 576 megapixels. After all, our eyes can move around within their sockets. By taking both estimates into account we can arrive at a safe middle ground of around 120-130 megapixels which is still a very high resolution compared to most modern, high-end cameras.
The resolution or detail of the human eye is another specification that is difficult to calculate due to our curved retinas and the way our brains interpret the images our eyes create. 20/20 vision for instance only applies to our central field of view. Outside of this, we can’t really interpret fine details. In fact, it’s estimated that just 20 degrees off the center of our field of view we can only interpret 1/10th the amount of detail.
And, as mentioned before. The final image in our brains isn’t a quantifiable number of pixels on a sensor. Instead, it’s a 3D interpretation of what our eyes are seeing. So how can we calculate the resolution of the human eye? Well, we can compare our eyes to cameras of different resolutions and measure how well they can detect fine details. And many people have done this. If we just take our sharp, central field of view and don’t take into account our peripheral vision then our eyes roughly equate to a 15-megapixel sensor. If we apply this resolution to our entire field of view, then we arrive at a sensor of roughly 576 megapixels. After all, our eyes can move around within their sockets. By taking both estimates into account we can arrive at a safe middle ground of around 120-130 megapixels which is still a very high resolution compared to most modern, high-end cameras.
ISO/Light Sensitivity
ISO, quite simply, is your camera's sensitivity to light. Before digital cameras existed, this was called film speed and referred to a variety of different rolls of film that were either more or less sensitive to light. With modern, digital cameras your sensor converts light into electronic signals. By raising your ISO on a digital camera, you are amplifying the strength of those digital signals. Many modern cameras can shoot at incredibly high ISOs in low light conditions with some of the best mirrorless cameras like the Sony A7 IV reaching numbers of around 256,000. So how does this compare to the human eye?
To measure this, we can compare images taken by a camera in different lighting situations to our own vision and come up with some numbers. Luckily, people have already done this, so I don’t have to.
In normal daylight conditions with bright sunlight, our eyes equate to an ISO range of about 1-1,000, which is crazy as most digital cameras can’t go below an ISO of 100. In low-light conditions, such as being under a forest canopy on an overcast day, our eyes’ native ISO is about 16,000. But where this gets really crazy is when we look at human night vision or our eyes' sensitivity to light when the sun sets. In this case, our eyes can achieve an ISO of about 800,000. After all, we switch from primarily using cones to rods at night as these photoreceptors are more sensitive and function better in the darkness.
ISO, quite simply, is your camera's sensitivity to light. Before digital cameras existed, this was called film speed and referred to a variety of different rolls of film that were either more or less sensitive to light. With modern, digital cameras your sensor converts light into electronic signals. By raising your ISO on a digital camera, you are amplifying the strength of those digital signals. Many modern cameras can shoot at incredibly high ISOs in low light conditions with some of the best mirrorless cameras like the Sony A7 IV reaching numbers of around 256,000. So how does this compare to the human eye?
To measure this, we can compare images taken by a camera in different lighting situations to our own vision and come up with some numbers. Luckily, people have already done this, so I don’t have to.
In normal daylight conditions with bright sunlight, our eyes equate to an ISO range of about 1-1,000, which is crazy as most digital cameras can’t go below an ISO of 100. In low-light conditions, such as being under a forest canopy on an overcast day, our eyes’ native ISO is about 16,000. But where this gets really crazy is when we look at human night vision or our eyes' sensitivity to light when the sun sets. In this case, our eyes can achieve an ISO of about 800,000. After all, we switch from primarily using cones to rods at night as these photoreceptors are more sensitive and function better in the darkness.
Dynamic Range
Dynamic range is how good your camera is at detecting both very bright highlights and very dark shadows. If your camera can detect variations in almost pitch-black shadows as well as in very bright highlights in a single image then it has a high dynamic range. High-end, modern digital cameras usually have a dynamic range of about 11-14 stops of light.
This is yet another technical spec that is hard to calculate. A camera captures a single image and has a set dynamic range whereas our eyes are constantly moving around and adjusting their aperture based on the brightness of specific subjects we’re looking at. If we calculate the dynamic range while allowing our eyes to adjust to different parts of a scene human vision easily surpasses 25 stops of light. If we compare a single “snapshot” of our eyes looking at one thing with a fixed aperture (pupil dilation) then we are pretty much on par with modern cameras at a dynamic range of about 10-14 stops.
Dynamic range is how good your camera is at detecting both very bright highlights and very dark shadows. If your camera can detect variations in almost pitch-black shadows as well as in very bright highlights in a single image then it has a high dynamic range. High-end, modern digital cameras usually have a dynamic range of about 11-14 stops of light.
This is yet another technical spec that is hard to calculate. A camera captures a single image and has a set dynamic range whereas our eyes are constantly moving around and adjusting their aperture based on the brightness of specific subjects we’re looking at. If we calculate the dynamic range while allowing our eyes to adjust to different parts of a scene human vision easily surpasses 25 stops of light. If we compare a single “snapshot” of our eyes looking at one thing with a fixed aperture (pupil dilation) then we are pretty much on par with modern cameras at a dynamic range of about 10-14 stops.
Shutter Speed
As I mentioned before it’s easier to compare human vision to a video camera as opposed to a stills camera. We are creating constantly changing scenes in our minds similar to the constantly changing frames of videos. That being said, we can attempt to calculate the relative shutter speeds of the human eye by focusing on when we experience motion blur. An example of this would be a fast-moving object that we aren’t tracking. If we’re looking straight forward and something rapidly moves in front of our central field of view without moving our eyes, we will experience a blurring of this motion at about 1/200th of a second.
As I mentioned before it’s easier to compare human vision to a video camera as opposed to a stills camera. We are creating constantly changing scenes in our minds similar to the constantly changing frames of videos. That being said, we can attempt to calculate the relative shutter speeds of the human eye by focusing on when we experience motion blur. An example of this would be a fast-moving object that we aren’t tracking. If we’re looking straight forward and something rapidly moves in front of our central field of view without moving our eyes, we will experience a blurring of this motion at about 1/200th of a second.
Frame Rate/FPS
Perhaps shutter speed isn’t a great camera spec to equate to human vision but a similar spec on video cameras that is much more comparable is frame rate. As our brains are constantly absorbing visual information from our eyes, at what rate are we processing this?
To start let's break down how we process visual information. The rods and cones that translate light into electric signals in our retinas have a maximum firing rate of 13 milliseconds which equates to about 75 times per second. It should be noted that these photoreceptors aren’t all firing in sync like the way a sensor is scanned on a camera. Instead, they all fire at different times sending a constant jumble of random information to your brain which then sorts all of this data and creates an image. So, once again it’s hard to quantify our eyes' maximum frame rate based on this knowledge.
What researchers have done, however, is test subjects on whether or not they can tell the difference between playback frame rates on screens and on how accurately subjects can identify images that are being shown for very short periods of time. A relatively trained eye can tell the difference between 60 and 120 fps playback on a large monitor and in a test with fighter pilots, subjects could identify specific planes when being flashed on a screen for as little as 1/220th of a second. In addition, some experts believe that the type of motion or movement you are seeing can alter the frame rate of the eye. Many believe that with specific subjects moving in the right way, our vision can match frame rates of up to 500 fps. With all these varying numbers it’s very difficult to come up with any sort of accurate average, so I’ll let you decide for yourselves. Can we achieve 500 frames per second or are we mostly limited to either 30 or 60 frames per second which are very common in playback speeds in films and video games?
Perhaps shutter speed isn’t a great camera spec to equate to human vision but a similar spec on video cameras that is much more comparable is frame rate. As our brains are constantly absorbing visual information from our eyes, at what rate are we processing this?
To start let's break down how we process visual information. The rods and cones that translate light into electric signals in our retinas have a maximum firing rate of 13 milliseconds which equates to about 75 times per second. It should be noted that these photoreceptors aren’t all firing in sync like the way a sensor is scanned on a camera. Instead, they all fire at different times sending a constant jumble of random information to your brain which then sorts all of this data and creates an image. So, once again it’s hard to quantify our eyes' maximum frame rate based on this knowledge.
What researchers have done, however, is test subjects on whether or not they can tell the difference between playback frame rates on screens and on how accurately subjects can identify images that are being shown for very short periods of time. A relatively trained eye can tell the difference between 60 and 120 fps playback on a large monitor and in a test with fighter pilots, subjects could identify specific planes when being flashed on a screen for as little as 1/220th of a second. In addition, some experts believe that the type of motion or movement you are seeing can alter the frame rate of the eye. Many believe that with specific subjects moving in the right way, our vision can match frame rates of up to 500 fps. With all these varying numbers it’s very difficult to come up with any sort of accurate average, so I’ll let you decide for yourselves. Can we achieve 500 frames per second or are we mostly limited to either 30 or 60 frames per second which are very common in playback speeds in films and video games?
So, there you have it. Perhaps I wasn’t able to provide incredibly accurate numbers of common camera specs when it comes to the human eye but at the end of the day, our eyes aren’t cameras. More than anything this was a fun experiment to learn more about what our eyes and brains are capable of. Perhaps cameras can outperform our eyes when it comes to specific tasks or capturing light in a controlled manner, but I won’t be trading my eyes for a pair of cameras anytime soon. When it comes to versatility and flexibility I can’t think of a single camera that can outperform our vision across the board.
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AUTHOR
Keenan Hursh is a Photographer, visual designer, and creative story teller based out of Bozeman, Montana. He draws inspiration from his frequent excursions into the natural world and always brings his camera along to capture whatever adventures he finds himself in. Keenan is passionate about documenting and sharing fleeting moments from the natural world and focuses primarily on wildlife, landscape, and adventure photography.
When it comes to gear, he primarily shoots digital with his Canon EOS R5 and EOS 6D mark ii but also has several 35mm film cameras that get out every now and then.
At a very young age, Keenan started bringing a camera along on his excursions and immediately fell in love with the art of photography. He started out with his parent’s cheap point and shoot and has continuously improved his craft and gear refining his shooting style and producing more compelling and intriguing images.
Growing up in the foothills of Boulder, Colorado, surrounded by mountains and wilderness, Keenan has developed a deep passion for many outdoor activities. When he’s not out on a shoot or using his camera, Keenan enjoys skiing, climbing, hiking, backpacking, cycling, whitewater rafting, and paragliding. If he’s outside, away from the distractions of society and civilization, he’s in his happy place.
Keenan studied Emergent Digital Practices at the University of Denver while minoring in Marketing and Entrepreneurship. Since earning his degree in 2019 he was worked with a wide range of clients, companies, and organizations throughout his career. Apart from photography he specializes in content creation, writing, brand development, and graphic design.
You can view Keenan’s portfolio on his website at www.keenanhurshmedia.com
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