We live in a world full of colors. Parrots, for instance, are a delight to watch with their vibrant feathers and charming appearance. each of the hundreds of parrot species is a wonderful work of art. The eye-catching colors of blue-and-yellow macaw are symmetrically distributed on the animal’s body. Its beak and neck are black, its face is white and decorated with thin black stripes, its forehead is green, its back and tail are blue, and its wings and abdomen are golden yellow. This distribution of colors results from specific pigments and structures: the black areas contain pigments that absorb all wavelengths of light, while the white parts are composed of materials that reflect all colors. The yellow, blue, and green sections are structured to reflect three different wavelengths from the white light.

This distribution of colors requires precise measurements performed at the atomic level. Each color in the parrot’s feathers is encoded in its DNA, directing the arrangement of atoms to reflect specific colors on different parts of its body. Pigments are synthesized to allow us to see light of a certain wavelength as a certain color.

The secret of green

Color can be defined as the image that forms in our brain – and is perceived by our soul – as a result of stimulation in our eyes by different wavelengths of light.

One question many of us wonder is why most of the plants are green. Why green and not blue or red? Shouldn’t plants, which are constantly exposed to the sun’s rays, absorb all colors and become black? [1].

The chlorophyll pigment is responsible for making plants appear green. It does so by absorbing a large part of the light spectrum and reflecting the green light. Plants survive and grow through photosynthesis, a process in which sunlight is used to produce glucose and store energy by synthesizing food from carbon dioxide and water. For all this to be possible, the Sun plays a key role.

In the visible spectrum, the most intense (most scattered) wavelength of light emanating from the Sun is green. In other words, the color that has the most energy is green. Green plants, which are expected to absorb all of this energy, have been found to reflect only a part of the green spectrum.

Green: The regulator color

Scientists studying the mechanism of photosynthesis have found that plants use the green spectrum as a regulator [2]. As the Earth rotates, the angle of the Sun’s rays constantly changes, altering the positions of branches and leaves relative to the Sun. Thus, and due to the rainfall and the movements of clouds, plants do not receive the same intensity of sunlight, that is, energy, at all times, because the spectrum is constantly changing. We can compare this to an electrical appliance that would be damaged if the power supply kept fluctuating. In such cases, regulators are used to adjust the voltage (220V or 110V) by decreasing or increasing the incoming electricity. Similarly, to optimize photosynthesis, which requires a stable amount of energy, plants adjust their color by regulating the light they absorb. This explains why plants sometimes appear dark green and at other times light green. The ability to regulate ever-changing solar energy is only possible by reflecting certain regions of the solar spectrum, producing various shades of green. By reflecting these shades based on their conditions, plants achieve more stable growth. This stability in plants is crucial to maintain the continuity in the chain of life in nature, ensuring the vitality of plants through the efficient harvesting of light.

The leaves of some trees, such as the species Liquidambar styraciflua, change color based on the angle of the Sun’s rays, adjusting with the seasons [3]. This wonderful phenomenon occurs as the color pigments in the leaves change. Thanks to this adaptive capacity given to plants, trees maximize their benefit from sunlight while transforming the landscape into a marvelous exhibition adorned with shades of green, red, and yellow.

Making the most of the Sun

Another point to note is that leaves are positioned to maximize their use of sunlight, an indispensable element of photosynthesis. From a distance, branches and leaves may appear randomly arranged, but when examined in detail, we come across a magnificent artwork. In every tree, the spot where branches grow, the arrangement of leaves around them, and even the symmetrical shapes of flowers follow precise mathematical rules. In addition to this, each plant has its own unique branching and leaf arrangement rules. These arrangements, often forming circular or spiral structures, are encoded in the plant’s DNA—similar to the Fibonacci sequence—ensuring that leaves do not shade one another and receive maximum sunlight. To optimize light absorption, leaves need to be flat, which is why leaves are created in this way. Photocell solar panels operate on the same principle [4].

Our eyes

The mechanism of vision can be summarized as follows: Light entering the eye passes through the cornea, pupil, lens, and the dark chamber before reaching the retina. At the back of the retina are cells that perceive light known as rods and cones because of their shape. Here, light is converted into electrical signals and sent to the brain. Cone cells are responsible for color perception and require bright light to function. Humans have three types of cone cells, each responding to different wavelengths of light. Each of these carries pigments that have varying sensitivity to light [5].

Electrical signals from receptors stimulated by light are transmitted to the brain via the optic (visual) nerve. Studies show that both cone cells (which function in medium to bright light) and rod cells (which function in low light) are most sensitive to green [6]. One reason we feel at peace in the woods is that green is the most restful color for our eyes. The fact that the most intense of the visible rays coming from the Sun is green shows that the One who created these rays, also created our eyes, and the phenomenon of seeing.

A healthy human eye can distinguish about a million different colors [7]. Just as painters obtain different colors by making mixtures of three basic colors, our eyes are created with pigments in three different cone cells to make combinations of different colors out of different wavelengths to recognize hundreds of thousands of colors.

Cameras and the color green

Cameras are devices invented by mimicking the human eye. Its contact with light, focusing mechanisms, cover, and lenses are all inspired by how our eyes function. The basic task of all cameras, including the ones in mobile phones, is to capture three colors (red, green, blue), just as our eyes do. Cameras have photo sensors that can detect these colors. American inventor Bryce Bayer, who discovered the sensitivity of our eyes to green light, succeeded in obtaining clearer images by doubling the green photo sensor in cameras [8]. This is how cameras today work.

Filming

Another area where the color green plays a role is in filmmaking. Green screen technology, also known as chroma key, is used to combine and edit two pictures or video streams. Green stands out more strikingly during post-production and can be easily manipulated. This makes it possible to film scenes set in battlefields or outer space—productions that would otherwise be prohibitively expensive—more affordably and efficiently.

Colors with short wavelengths, such as yellow and red, which evoke the Sun and fire, are called warm colors. In contrast, colors with long wavelengths, such as purple, navy blue, and blue are classified as cool. Green is in the middle of the spectrum.

The reason leaves turn yellow and red as autumn and winter approach is due to the breakdown of chlorophyll molecules, which leads to the production of new substances that interact with light differently. Pigments in the flavonoid and carotenoid groups serve various functions, including protecting chlorophyll from excessive ultraviolet exposure. Red and purple hues come from anthocyanins, orange shades from carotenoids, and yellow tones from xanthophylls. This vibrant display of colors not only adds beauty to nature but also reminds us that such a masterpiece cannot come by chance.

The solar spectrum reaches its highest value in green. In other words, the most intense (most scattered) wavelength of light scattered from the Sun in the visible spectrum is green.

And whatsoever He has created for you on earth of varying colors (and diverse forms and qualities): surely in that is a sign for people who reflect and are mindful. (an-Nahl 16:13)

Notes

• Since sunlight is made up of a mixture of all colors, when you go into space, it appears white, which is its true color. It appears yellow on earth because of our atmosphere, which acts as a filter.
• Trevor B. Arp ve ark. “Quieting a noisy antenna reproduces photosynthetic light-harvesting spectra”, Science, 368/6, 26 June 2020.
• “Liquidambar styraciflua”, en.wikipedia.org/wiki/Liquidambar_styraciflua
• “Solar Energy”, www.nationalgeographic.org/encyclopedia/solar-energy
• Arif Sarsılmaz, “I Am Hasan’s Eye”, Sızıntı, August 2000.
• Katarzyna A. Hussey ve ark. “Patterning and Development of Photoreceptors in the Human Retina”, Front. Cell Dev. Biol. 10/878350, 2022.
• “How human eyes see different colours”, osmosmagazine.com/science/biology/how-human-eyes-see-different-colours/
• “Bryce Bayer”, en.wikipedia.org/wiki/Bryce_Bayer

Airborne drones are becoming commonplace, especially in the civilian world. Unmanned aerial vehicles (UAVs), also known as drones, are aircrafts controlled by a pilot from a remote location on the ground. Drones are increasingly being used, and not just for military purposes. They’re used for agriculture, disaster response, energy production, environmental monitoring, construction, and sports activities. Their use has expanded exponentially in recent years, spurred by technological advancements and easy access to affordable high-tech parts. Drones can fly from several minutes to several days, depending on the technology and the mission, and the cost of having a drone ranges from a few hundred dollars for hobbyists to millions of dollars for military purposes. But as happens with most major technological changes in a society, the increased role of drones is raising privacy and public safety concerns.

Although drones are unmanned vehicles and depend mostly on human intelligence, adaptive control systems and artificial intelligence technologies can allow drones to fly without human intervention. Drones are increasingly becoming autonomous, following a pre-programmed mission, and can even make their own decisions while gathering and sending data back to a ground unit.

Drones are becoming popular for military purposes. They are cheaper than a military aircraft, and flying them remotely means there is no danger for the flight crew. Small drones can get into places where humans cannot, and large drones can fly into war zones to gather surveillance or to take part in military strikes. On the plus side, this will reduce the number of active military personnel in war zones, and reduce casualties. Even the possibility of replacing human drone operators with computer algorithms is in discussion, leaving a machine to make the final decision about whether to end a civilian life or to destroy vital infrastructure (this decision is also called the ‘signature strike’). [1]. Such a possibility raises serious questions about the ethics of war, privacy, and public safety.

Law enforcement officers are already using drones to detect people illegally crossing their nation’s borders. It is already in use by cities in the US for monitoring criminals, for crime fighting, car chases, executing search-and-rescue missions, firefighting and basic surveillance. People are interested in using camera-equipped drones to patrol their homes during police raids, to collect their own evidence.

Another proposed use is in the protection and inspection of infrastructures, and monitoring power lines, dams, levees, and gas pipelines to reduce the cost and manpower for these dangerous, dull, and costly jobs. If they are intelligently deployed in civilian life, drones can be useful in keeping people out of harm’s way.

Drones can assist in search and rescue missions after tornadoes, earthquakes, floods and other natural disasters, especially in places not reachable by, or dangerous to, humans. They can locate survivors and report their location to the ground base [2]. Drones can fly through the dark, pick up heat signatures of bodies using infrared cameras, see through smoke using thermal cameras, record footage using night-vision, and pick up hard-to-hear sounds in dangerous locations. Since they are small, they can easily be transported and deployed in disaster areas, and be up in the air in minutes compared to the longer time requirements required for planes and other rescue vehicles.

An example of this is drones that are already in use monitoring abused wildlife in Kenya and rescuing injured skiers in France [3]. Drones are also extremely useful in monitoring wildfires with minimal cost and little risk of loss of life. NASA is already using drones for monitoring hurricanes, the National Oceanic and Atmospheric Administration (NOAA) is monitoring wildlife in the Arctic, and the US Geological Survey (USGS) is mapping remote terrain and performing environmental research.

Drones are becoming an important part of agricultural production. They can help farmers to check if their fields need watering or fertilizing. In Japan, drones are used for precision agriculture, where drones fly over a field and use multispectral cameras to take pictures of the crop and analyze if it is over-watered or under-watered. This allows farmers to precisely determine the right amount water and pesticide to use, and this helps them decrease costs and increase the crop’s yield.

An interesting application of drones is in clean energy production. Some companies are already exploring the use of drones as autonomous wind turbines that would be flown like mechanical kites [4]. The goal is using drones equipped with wind turbines to fly to higher altitudes, where more consistent and powerful wind is available to be harnessed. These drones are lighter and cheaper than wind turbines, and can adjust themselves to the wind streams to maximize their energy harvesting.

Drones are also used by the construction industry. They provide a cost effective way to check the progress of a construction project, help managers inspect hard to reach locations, take architectural photographs, create 3D scans of a building using infrared cameras, survey more precisely, undertake comprehensive safety inspections, and even replace some of a project’s manual labor. Drones recently demonstrated their ability to assemble, brick by brick, a 1:100 scale model of a skyscraper. Researchers are investigating more potential applications of drone technology in construction sector [5].

The most common use of drones will likely be by hobbyists, who have access to cheap, light, camera-equipped machines that can be controlled by smartphones and tablets. Athletes and extreme sports hobbyists are using drones to capture their activities and tricks during snowboarding or skating outings. Climbers have drones follow them for safety and to record and report their progress to base camps. Drones are increasingly being used by amateur or professional photographers to capture footage. While hobbyists can buy drones ready to fly out of the box, many are going the Do-It-Yourself (DIY) route to create customized, specialized aircrafts. Drone hobbyist websites have more than millions of members, and are growing every day. People exchange their experiences, pictures, and schematics, thus enabling their fellow hobbyists to improve their own drones.

Autonomous drone technology is not limited to the skies. Seaborne drones are already deployed in the ocean to monitor coastlines and passageways for pirates [6]. They communicate with an airborne drone for intelligence and can be picked up by a ship or submarine after the mission is completed. They need to be equipped with capabilities to survive for a long time in cold and corrosive seawater, and to tackle the challenges of underwater communication.

The drone industry is growing fast, and is estimated to have created 70,000 jobs and made an economic impact of $13.6 billion in its first three years. With all the benefits this new technology is contributing to our lives, the domestic use of drones has grown; but so have concerns about their privacy, safety, and regulation. Many people are concerned about their potential for abuse. One of the suggestions for government use of drones is limiting their use to a few purposes determined by the law, and specifically for emergency and public safety. Hobbyists and recreational users do not need any special license to fly a drone, but they are encouraged to follow guidelines outlined for public safety. The guidelines mainly suggest operating drones at a sufficient distance from populated areas, and not over or near private properties or lower than 120 meters in altitude. One of the main concerns about the public use of drones is the ease of weaponizing them; they could conceivably be used to attack private targets.

In science fiction movies, intelligent systems and drones can become self-aware and cause serious problems. It is unlikely that drones will become self-aware anytime soon, but that doesn’t mean there aren’t any safety issues about drones. As seen with most secure computer systems, drone can be hacked by a malicious person or group. These groups can take control of the vehicle, access its video feeds, alter data and information sent to ground control units, and spoof GPS systems to manipulate the drone to land or attack a different target.

When technological breakthroughs are achieved in critical areas, as in drones, a series of solid scientific research needs to be conducted before populating the civilian market with the technological products. Governments and civil societies have an important role in regulating the usage of drone. Some of these steps include requiring a warrant for deployment, limiting the data retention time for images and video feeds, establishing an accountability mechanism, and prohibiting the weaponization of domestic drones.

Acknowledgment: This article was produced by Mergeous [7], an online article and project development service for authors and publishers dedicated to the advancement of technologies in the merging realms of science and spiritual thought.

Halil I. Demir is an internet entrepreneur and freelance writer.

References

[1] T. Zakaria and M. Hosenball. “U.S. Drone Guidelines Could Reduce -Signature Strikes,” The Huffington Post, May 23, 2013.

[2] H. Kelly. “Drones: The future of disaster response,” CNN, May 23, 2013.

[3] A. Levy and M. Milian. “Future of Drones: Aerial Assassins or Helpful Hovercrafts?” Bloomberg, May 15, 2013.

[4] K. D. Atherton, “Google Bets $10.7 Million On Drone Intelligence,” Popular Science Magazine, May 16, 2013.

[5] R. Von Ins, “Rise of the Drones,” Georgia Institute of Technology, January 23, 2013.

[6] J. Emspak, “Schools of Sleeper Drones Could Swim Future Seas,” Discovery News, January 25, 2013.

[7] Mergeous, Online article and project development service, mergeous.com

According to a study by researchers of the Human Footprint Project [1], humans have influenced 83% of the earth’s surface. The study is based on four factors: population, travel routes, land use, and lights. One of the findings of the study shows that an average American is responsible for more carbon emissions in one year, than a person in Tanzania in a lifetime. This significant difference is certainly related to the average lifespan, income, culture, and climate. However, do any of us have the rights to disturb the environment more than others? Are we consuming something that doesn’t belong to us, and leaving an unsustainable environment for future generations? To answer these questions, it is imperative that we understand and acknowledge exactly what we have inherited, what we are responsible for, and what we will leave to future generations.

Our influence on the earth and environment in a general sense is not limited to the consumption of goods. One of the most influential yet less-visible traces is the footprint we leave in the digital environment. There are active or passive traces left in a digital environment by personal activity. An active trace is left when personal information is released by a person himself, whereas a passive trace (digital shadow) is left when personal data is collected during personal activity. These traces, also known as digital footprints, can spread very quickly and may reach to millions in a very short time. One can leave digital traces by simply visiting a website, sending a blog post, or posting a photo or message to a friend’s website.

Our digital traces affect the environment in many ways. Every trace takes our time to generate it and for others to read it. It consumes storage and network resources on the server that increase the costs, power usage, and eventually our carbon footprint, or the total greenhouse gas emissions. We need to seek a balance in our use of digital media in order to utilize the benefits efficiently and to minimize our consumption of time and other resources.

Have you ever wondered “how often a person leaves digital traces behind every day?” or “how much of our privacy are we sharing with others?” A recent study reveals some figures about the size of the digital universe as 281 billion gigabytes (GB) for 2008 and 1.8 billion terabytes for 2011 [2]. The digital trace generated by the average person on a daily basis was about 45 GB in 2008. This includes private information such as emails, photos, VOIP calls, and instant messages.

How about passive digital traces we leave behind by credit card purchases, bank accounts, phone records, web searches, general backup data, medical and hospital records, surveillance cameras, and so on? There are more passive traces collected than our active digital traces, which provide more personal information.

As of 2006, there were over 1 billion Visa credit cards worldwide and counting [3]. Credit cards give a lot of private information about a person: stores we prefer, movies we watch, places we travel, books we read, prescriptions we take, rent and utility fees we pay; mainly our lifestyle is hidden in our credit card statements. It might contain a lot of details we want to keep private. We can easily learn a lot about our social life just by analyzing one of our credit card statements.

Web searches provide more insightful information about a person. 113 billion web searches were conducted in July 2009, a 41 percent increase compared to 2008 [4]. Besides all the information we leave with our credit card, web searches may show things we have not actually done. They contain information about our future plans, such as travel, job search, health related issues, meetings, and education. Websites can provide smarter search results and personalized advertisements according to our search habits. Search engines even know how fast we type or process information, our typos, languages we speak, how smart we search, and even our physical location from the IP address.

Today many cars have GPS (Global Positioning System) capabilities and smart phones have GPS sensors. GPS devices can show our exact location anywhere in the world, provide turn-by-turn instructions from one location to another, provide a list of nearby stores, and warn us about traffic problems. A recent market research [5] estimates that the mobile location technology market that crosses the US will be $75 billion by 2013 with growing usage of GPS capabilities in automobiles and consumer electronics. Beside all the benefits, GPS devices leave an important digital trace behind, our exact location, which can be stored for later use or tracked by third parties.

Even if a person doesn’t have a GPS sensor with him, there are cameras all around the city that can help capture one’s location. We can see cameras inside and outside of the banks, stores, traffic lights, and even closed-circuit TV (CCTV) surveillance cameras in some cities. The total number of CCTV cameras in England is 4.2 million, or one for every 14 people according to an estimate. According to Scotland Yard, one crime per 1,000 CCTV cameras is solved in a year [6].

The number of smart phones increased 13.9 percent worldwide, compared to 2007, and reached 139 million in 2008 [7]. Many smart phones have real-time video streaming capabilities and are widely used. Users upload hundreds of thousands of videos per day to YouTube about themselves or people around them. Considering that there are thousands of video sharing websites like YouTube, sharing videos on these websites lies at the center of important privacy concerns. There are websites to share videos, photos, music, location, blog posts, and personal updates. With the rise of the micro-blogging trend, we can see real-time updates about a person on websites like Twitter. This allows us to track every minute of a person’s life.

Social networking is a new way of communication. Many websites provide tools to build online communities of people, who want to share and learn interests and activities of others. We can build our friend list and share photos, videos, and updates about our life. According to Nielsen Online’s report on Internet usage in June 2009 [8], users spent an average of 4 hours and 39 minutes during June on one of the most famous social networking sites, Facebook, which has 87 million visitors. Normally these websites provide privacy settings to limit who can access our friend list, photos, or other information. Since most of the people don’t refuse friend requests, it is very easy to be added as a friend and get access to all the private information of people we do not even know. Once we get accepted by a person as a friend, it gets easier to be accepted as friend by his/her friends, since we have mutual friends. These connections increase our friend list exponentially.

I had known about this process for some time, so I wanted to confirm it myself by setting up an account with fake information and identity on Facebook in 2008. I selected a college and input random personal information to my profile. I visited some group pages on Facebook and joined them. Then Facebook started to offer possible friend lists that have common interests with me. I started to make random friend requests to many users on these lists. In one day, I had around a hundred friends in my list that I don’t know personally. As a friend on their list, I have access to all information they share with others. Most of the users are using default settings and are not aware of privacy issues. Even if we are careful about all these settings and our privacy, our information is accessible by website managers. Digital traces left by users are valuable commercial assets for companies, and most of them share or sell this information to third party companies which provide online advertisements, products, and services.

There is a positive side of these digital traces. Websites provide better recommendation of products and services, targeted advertisements, smarter search results, and personal news. Entertainment businesses can provide appropriate suggestions by using location services. However, erasing our digital traces is difficult or even impossible in some cases. To protect our privacy and identity, it is essential that we are aware of places our personal information is stored. It is the responsibility of websites to protect user’s data. However, it will be a good start to be aware as users of our traces on the digital universe and to share personal information carefully.

With various effects on our natural and social environment, digital traces are one of the most influential and yet less known by-products of consumption. It is an important responsibility for us to decide how we affect our environment, how we spend our time, and what we are going to leave to future generations. With all the unique values given to humans, we need to learn to make meaningful contributions and carry more responsibility for our actions, especially in the digital world where boundaries are unlimited.

Acknowledgment: This article is produced either in part or a whole at MERGEOUS [9], an online article and project development service for authors and publishers dedicated to the advancement of technologies in the merging realm of science and religion.

Halil I. Demir is an internet entrepreneur and freelance writer.

References

1. Wildlife Conservation Society [http://www.wcs.org/humanfootprint]
2. EMC Report, “The Diverse and Exploding Digital Universe,” 2008.
3. Visa USA Internal Statistics, Q4 2006.
4. ComScore Press Release, August 31, 2009.
5. RNCOS Market Research Report, “World GPS Market Forecast to 2013,” April 2009.
6. Telegraph, 24 Aug 2009.
7. Gartner Press Release, Worldwide Smartphone Sales, Mart 2009.
8. Nielsen Online’s Report, June 2009.
9. Mergeous [http://www.mergeous.com]

The four main functions required for life, namely the digestive, respiratory, circulatory, and excretory systems are all found in plants but performed by different organs. If these functions are non-existent the dynamism or the essence of existence that we call life will disappear and death is inevitable. If these four functions (digestion, circulation, respiration, and excretion) are in working order, it means an organism is alive but only at the level of plant life. To reach the animal level of life, in addition to the four main functions, functions like senses, nervous and muscular systems are also required.

If these functions fail, life continues, but at the level of plant life. We sometimes hear people saying “in a vegetative state.” When you hear this, people are usually talking about a person who has lost the use of the animal functions. He or she may be unable to see, feel, hear, or move. Intelligence, comprehension, will power, conscience and the many other special aspects of human beings cannot be compared with the essential functions of living; these are additional characteristics of being human which accompany the animal system of functions and emerge in relation to a person’s spirituality. This obviously does not mean that those who have lost their abilities are less human and they do not have any rights; on the contrary, it means to say that they are not responsible any more.

The focal points of sensory functions of sight, hearing, touch, taste, and smell are found within the head in the brain, which is the command center of our body and the most complex form of existence we know of in the universe. The brain is connected to the nervous system which communicates with all the organs in the human body. This is why the head is so precious; it is a very sensitive part of the body and has to be protected like a jeweler guards precious stones. If you tread on a nail, it may hurt for a while, but with treatment the wound can be cured. But if a nail were to penetrate someone’s head, this could damage any of the sensory functions or, God forbid, could even result in death.

As you have probably understood from our introduction, the head is firstly the center of animal functions then the focus point of the addition of the human senses. When you mention the head we are the first thing that comes to mind: the eyes. Did we hear you ask why? It’s because we are what you are reading these words with right now, and because you can see the beautiful creations of the universe with us-that’s why.

If my Creator had not created us and positioned us in the two cavities on your head, you would have no knowledge of the beauties of light, color, insects, flowers, roses or birds. You would be afraid to walk without us because you would have no idea where you are about to tread. The effect of sight can only be sent through us to your brain and reflected into your mind. The development of human knowledge would have been very delayed if God had not created us or the other sense organs because the only way to gain knowledge is through healthy sense organs. The sense organs are the only way of detecting and recognizing the characteristics of objects.

You need us to realize that water is transparent, apples are red, quinces are yellow and violets are purple, you need us to recognize your mothers, fathers and friends. You need us to eat, drink, read and write and so you do not bump into walls. What do you think will happen if we close our lids for ten seconds and you try to walk down the street? Try it if you want!

You see-it was harder than you thought. You were scared in case you bumped into something or fell over. Look, Peter, just take a deep breath and give praise to our Creator while our lids are closed tight, for you could not tolerate being in the dark for a mere ten seconds, so what if you never saw the light? Just think sometimes about people who are not as fortunate as you, who cannot see for one reason or another. Give praise to our Creator for not giving you such a trial, and pray for the patience of those friends who have been deprived of sight.

Yes, now we have come to our characteristics and delicate creation, so pay attention. When Darwin saw God’s magnificent skill in our creation, he realized that we could not have been just a coincidence or a self-made creation, and it was impossible for us to be a creation of unconscious nature. Due to the guilt he felt inside, he found it necessary to say that the idea that “the evolution of complex organs like the brain and the eye could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.”

There is no artificial optical device that can match the esthetics or precision of our creation. Our operating principles depend on the optical laws God Almighty has determined for the light. As a matter of fact, just by looking at our structure, human beings worked out the rules of optics, you made the simplest of cameras, and you went on to produce the most magnificent photographic cameras possible. But whatever you do, never try to compare one of us to those cameras you have invented or you may become rather embarrassed. Your cameras are a simple toy compared to us. From the time of the invention of the old, wooden box cameras that had to be covered with a black cloth up to the modern digital cameras of the present, 175 years have passed. Many people worked for years to bring cameras to such a perfect state. Can anyone claim that the old camera made of a wooden box and a lens evolved by itself and turned into the high-quality, digital cameras of today? With all the knowledge accumulated by hundreds of scientists over the years, can this invention really be called a coincidence? So, can we be a coincidence? Could the eyes of mollusks or insects make themselves evolve and transform into the eyes of humans? Of course not! But to understand this a little better you must pay attention to our structure.

We are globe-shaped and look like covered capsules with a multi-layered structure which is quite solid and supple (Figure 1). Each of us is approximately 24mm in diameter. We have an outer layer made of something called sclera (hard coating). We are protected by a strong cover made up of dense ligament fibers, and beneath this is the choroid layer (a layer of blood vessels), where the blood vessels nourishing us go into; this layer covers us completely like a network of vessels. In the middle of the eye is the retina which is a layer of film. It is located in the most precious place where our actual receivers of light reside. There are other layers which each have their own duty beneath these layers, but we won’t go into too much detail.

We each have a main casing that is round and has a dome-shaped surface which slightly protrudes. The center of the hard coating, the cornea, is transparent so that it will allow light to pass through. On the outer part of the transparent area is what they call the white of the eye, and the whole areas seen from the front is covered in a clear membrane (the conjunctiva) with mucus cells. This keeps us lubricated. So as to focus light rays, our cornea section is more curved than other sections. There is a tiny chamber behind this curved front and this is actually where the lens, which separates the main chamber, is found. In the front chamber between our lens and cornea is a transparent liquid, the iris, which gives us our color. The black hole in the center of the iris is called the pupil. The iris, which has a special structure of muscles, works like a curtain contracting and expanding our pupil in response to the brightness of light. If the light is powerful, it contracts to protect the retina from any damage, whereas if the light is dim, the iris expands the pupil to allow more light into the retina.

The fibers (zonules) that hold the lens suspended in place and the cluster of muscles (corpus ciliare), which changes our lens according to the focus distance, are in front of a layer of blood vessels. Our lens, which plays a role in focusing, changes shape and adjusts according to whether the focus point is near or at a distance by thinning and thickening. We do this with the help of the fibers that keep the lens suspended.

Behind the lens is a larger chamber filled with a jellylike, transparent liquid (vitreous humor). The pressure and consistency of the jellylike liquid ensure that we keep our round shape. There are photoreceptive cells in the shape of rods and cones which are sensitive to light in the dark chamber behind our retina. The visual images formed by the rays which pass through the cornea and lens to the retina are upside-down. There is a small pit in my retina where almost every cell has a light receptor cell. This is where your sharpest vision is formed, but that doesn’t mean that it is where you actually perceive the object you are looking at. Sight is what happens when a group of cells in the brain’s visual center is stimulated, and the images on our lens are comprehended. It is unbelievable how fast is the effect of the chemical and electro events on our light receptor cells. The effect of light is conveyed to your brain through the stimulation of electric signals in our receptors’ optic nerve where the actual vision is produced in the brain, so in a way we are just the means of vision.

Because we are such delicate and sensitive organs, our Creator placed us in the cavities within the bone structure of your head for protection. We fit in the very strong and secure structure comprising your chin bone, cheek bones, forehead bone, orbital bone (just around us, your eyes), nasal bone and occipital bone (at the rear and bottom of your skull), but this is not our only protective mechanism. We have top and bottom eyelids that we close to protect ourselves from oncoming dangers. The frequent blinking of our eyelids prevents our cornea from becoming dirty, just like the windscreen wipers of a car. Our eyelids are not just simple folds of skin, they are a secretion system of glands which continuously lubricate the inner part of your lashes and seize dirt and dust, turning them into harmless particles. When you feel emotion, the secretion produced by the tear glands between us and the nose fills the tear ducts, passes through the two canals, and gives us a good wash. But when you cry too much, the excess secretion empties through another canal, which also washes your nose.

As this system is complex, it can also go wrong sometimes. If you consider our many parts and our millions of cells you will clearly see the possibility that any one of our components may fail. However, our Creator has formed the eyes in most people’s heads without any defect or failure, so we can serve you with vision of the universe.

The Creator gives us something called illness so we are reminded of our weakness, a defect or failure which arises as an act of wisdom. Some illnesses, like diabetes, deficiency of vitamin A or atherosclerosis, may have a negative effect on us and even render us useless. We eyes also have some defects which occasionally appear, such as not being able to see at a distance, or close up. Focus defects are easily remedied with spectacles or lenses, but faults in the sensitive light receptor cells in the retina are more difficult to amend. The pressure of the liquid in our larger chamber must be correctly balanced. If this pressure increases too much, we will give you a great deal of pain due to what doctors call glaucoma. If we lose our transparency, your vision will become clouded by what is called a cataract. Apart from this, there are many viruses and bacteria that can cause infections and diseases, but the cells of your immune system are like soldiers who, with the Creator’s help, protect you from those bacteria and viruses.

Look, Peter! It would take pages and pages for us to explain ourselves to you, but we don’t really want to confuse you with even more anatomical information. Our whole aim is to explain the reasons for the creation of our parts, to astonish you with the wisdom and fine art of the Divine, so you will contemplate the wonders of creation and give praise to the Almighty for the blessings he has bestowed upon you. If we have been successful in achieving this, that would be the greatest reward we could ask for.

Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.

Human beings are visually-oriented in their daily life; they use the sense of sight more than any of the other senses with which they have been endowed. The modern understanding of human vision and the underlining principles were only discovered in the past couple centuries. The nineteenth and twentieth centuries witnessed the development of photographic and digital imaging camera systems, which partially mimic human visual systems. We will open a small window on the history of human vision and camera systems, and try to compare today’s state-of-the-art cameras with the human visual system, focusing mainly on solid-state image sensors, or camera chips, and the image-sensing element of the human visual system, the eye.

History of human vision

Human vision has been the subject of conflicting interpretations since ancient times. Many ancient physicians and philosophers believed in the theory of extramission, or the active eye. According to this theory, the eye perceives objects by emanating light and seizing objects with its rays. It was in medieval Islamic culture that research on human vision and optics developed into a system similar to the modern theory of vision. Among others, Ibn Al-Haytham (Alhazen) (965-1040 A.D.), a Muslim physicist, astronomer, and mathematician in the tenth century, played a great part in this field by promoting the intromission theory which states that vision only occurs because of light rays entering the eye. Ibn Al-Haytham founded physiological optics, which distinguished the functioning of the eye from the behavior of light. On the other hand, ten centuries after Ibn Al-Haytham, Winer et al. (2002) have found recent evidence that as many as 50% of American college students believe in the extramission theory.1

Although the fundamental features, anatomy, and physiology of the eye were documented by Galen (129–200 A.D.), an ancient Greek physician, in the second century A.D., it was Kepler, a close reader of Ibn Al-Haytham, who offered the first theory of the retinal image and the correct operation of the eye in 1604. He proclaimed, “Therefore vision occurs through a picture of the visible things on the white, concave surface of the retina.” Progress came slowly after Kepler, because little was known about the nervous system until the nineteenth century, and only recently have scientists acquired a more knowledge about how the brain apprehends the retinal image. But many questions still elude us.

History of the camera

In parallel with curiosity about human vision, human beings have also tried to mimic human vision by capturing images of objects with instruments. Around 1000 A.D., Ibn Al-Haytham, also known as the father of modern optics, invented the pinhole camera,2 and explained why the image was upside down. It was Johannes Kepler who further suggested the use of a lens to improve the pinhole camera in the 1600s. Capturing an image on a photographic plate was first achieved in the early 1800s. Consequently, photographic cameras began to be mass-marketed in the twentieth century. The photographic equipment with which we are all familiar today, such as the 35mm camera, flash bulb, Polaroid camera, and the point-and-shoot auto focus camera, all were developed in the twentieth century. The invention of the camera as we know it today paved the way for other technologies, including the moving image capture, and, later, the digital camera, in which electronic image-capture devices were used. In 1972, chemically processing an image onto photographic paper no longer became the sole destination of an image, because the first filmless electronic camera was patented by Texas Instruments Corporation. Filmless electronic cameras were made possible with the invention of solid-state image-capture devices called charge coupled devices (CCD) and metal-oxide-semiconductor (MOS) image sensors in the late 1960s. Since the invention of solid-state imagers, people have become more visually stimulated and oriented than ever before in history.

A comparison of camera chips and the human eye

The technological advancements of solid-state image-capture camera chip design and manufacturing during the past twenty-five years has made digital imaging more affordable and accessible to the general public. These advancements have become more visible to consumers in mobile products, particularly in cellular phones, in which there are still and video-camera functions. Although digital cameras are easily available today, the state-of-the-art image sensor chips used in these cameras exhibit a performance gap when compared with the capabilities of the human eye. How good these image sensor chips are today when compared to our eyes is a question that will be elaborated on.

It is possible to compare the capabilities of the human eye and state-of-the-art image sensor chips used in cellular phones or in mainstream PC and digital still cameras. It is also possible to compare the capabilities of the human visual system, including the eyes, the optic nerve, the visual cortex, etc. with a digital camera system which includes optics, image-capture and signal-processing chips and other camera apparatuses. The capabilities include ability to see different colors (spectral response), photo-element (pixel) characteristics (size, density, distribution), light sensitivity, light-intensity response range, functionality and operation modes, and signal processing capabilities.

Spectral response

A single light-sensing element in a solid-state image sensor is called a pixel. In the human eye it is called the photoreceptor. Both elements convert impinging light or photons into electrical signals. The human eye sees in the so-called visible spectrum, between 380nm (blue) and 750 nm (red), and utilizes two kinds of photoreceptors on the retina; rods and cones. The cones are used for color and daylight vision. Rods are responsible for night vision. There are three types of cone photoreceptors on the retina that contain different types of photosensitive pigments. The three types of cones are L, M, and S, and they have pigments that respond best to wavelengths of light that are long or red (peak at 564 nm), medium or green (peak at 534 nm), and short or blue (peak at 420 nm), respectively. The rods (R) are most sensitive at a wavelength of approximately 498 nm (green), as seen in Figure 1.3 Image sensor pixels in digital cameras mimic the photoreceptors in the human eye for color vision. They utilize three kinds of color filters (red, green, blue) on top of each pixel to convert light rays into electrical signals in different visible spectrums. Unlike the cones in the human eye, camera pixels and color filters can be designed to cover wide spectrums that are not visible to the human eye, for instance, the x-ray, ultraviolet, and infrared spectrums. In the category of spectral response range, camera pixels exhibit greater flexibility than those of the photoreceptors of the human eye. On the other hand, interestingly enough, the eyesight that humans possess has similar spectral characteristics as the sun. The solar light emission peaks in the visible spectrum as seen in Figure 2.4

Figure 1. Spectral absorption curves of the short (S), medium (M), and long (L) wavelength pigments in human cone and rod cells.3

Figure 2. The daylight solar spectral power distribution on earth.4

Pixel and array size

The size of pixels in today’s modern digital cameras is getting closer to the size of the photoreceptors in human eye. The typical human eye contains an average of 130 million photoreceptors. The diameter of the rods and cones varies between 1.0m and 8.0m, depending on their location on the retina.5 Today’s state-of-the-art image sensor chips contain 10 to 30 million pixels. Each pixel can be as small as 1.4m in diameter. To date there has been no image sensor that is 1.4m pixel in size or more than 8 million pixels. However, the human being has been equipped with photoreceptors that are as small as 1.0m and has more than 100 million photoreceptors; and this is since the beginning of existence. It is also estimated that the resolution of the human eye is equivalent to an imager sensor chip of 576 million pixels with a 120 degree field of view.6 Thus we still have a long way to go in improving the image-sensor pixel and array sizes used in cameras if we are to match the human eye.

Pixel distribution and formation

In the human eye the photoreceptor size and densities change, depending on their location on the retina. For example, no rods exist on the focus center of the eye, which is called the fovea. Color vision photoreceptors, which total only 10% of the eye’s photoreceptors, are located mostly on the fovea. There is an irregular distribution of photoreceptors which is unique for every human being, like a fingerprint. Yet, we all see things the same, such as colors (with the exception of people who are colorblind). In camera chips, however, pixels are arrayed regularly, in two-dimensions. As the image-processing techniques and algorithms used in camera systems are linear and do not closely mimic the signal processing that exists in the human visual system, regularly arrayed pixels are required.

Light sensitivity and response range

Although the pixel sizes in image-sensor chips are approaching the size of the photoreceptors in the human eye, camera systems are not yet close to being able to match performance in terms of light sensitivity and response range. The human visual system and photoreceptors can easily adapt to very dim and bright light, with a light-intensity response range of ten billion to one (1010:1).7 This response range goes from light conditions on a bright sunny day to dim night vision. Typically, a conventional consumer camera pixel has a light intensity response range of one thousand to one (103:1).8 In a camera system, details of a captured scene are either concealed in the dark regions or washed out by the bright light, depending on the exposure settings of the system. Thus, one could say that the human visual system works ten million times (107) more efficiently than that of consumer cameras in terms of transferring scenes into images.

Operation principle

In terms of operation principles, the photoreceptors in the human eye convert light rays into electrical signals with extremely rapid electro-chemical reactions which can detect a single photon. Typically, in the image sensor pixel of a digital camera the photoelectric effect is used to convert impinging photons into electrical charges. Electrical charges are collected and stored in each pixel during the exposure period. Collected electric charges in each pixel are amplified and converted into digital ones (logic-1) and zeros (logic-0) during image readout before the image is sent to higher processing elements, such as a personal computer, digital-still or video camera. It is possible for a single photon-counting camera to be developed. However, very special and larger pixel sizes and extra apparatuses are required to build such a camera system. Thus, we could say that it is almost impossible to build imaging pixels that have the capability and dimensions of the photoreceptors of the human eye with today’s state-of-the-art technology.

Signal processing capabilities

The captured image in the human eye is preprocessed before it is sent to the visual cortex of the brain. This preprocessing consists of a data reduction operation in which nothing is lost, with a compression ratio of 130 to 1, as only 1 million optic nerves leave each eye carrying the information from 130 million photoreceptors. This compression allows the brain to process information at a rate of 25 to 150 scenes or frames per second. Typically, every pixel in an image sensor chip is first transferred to higher processing units. A data compression method is either carried out with some loss of details in the image or the compression is never used. The transfer of frames in camera chips typically takes place sequentially, reducing the speed of the image-capture operation or frame rate. Different techniques are used to maintain a capture rate of, at most, 25 frames-per-second in camera chips. With today’s technology, image sensors that have a capture rate of one million frames per second have been proposed and can be manufactured for scientific applications.

The inherent inefficiencies of image-capture in today’s image-sensor chips are hidden by employing the limitations of the human eye. For example, solid-state image sensors have always been produced with row or column-vice uncanny stripes which are easily picked up by the human eye. However, psycho-visual experiments have shown that the human eye can only detect contrasts between two adjacent gray lines when the difference is greater than 0.5%. Thus, if a camera chip is designed to have a column to column or row to row contrast of less than 0.5%, these odd stripes would not be visible.

Conclusion

Humans are visually oriented and without a doubt, our eyes are considered to be our primary source of information. It is obvious that the human visual system is extremely complex and this complexity has fascinated human beings throughout history. Yet, the underlining principles and basic functions of human vision and the eye have only been discovered during the last two centuries. These discoveries have led research in how to mimic these functions, which has resulted in moving and still-photographic and camera equipment, and the image sensors chips used in digital cameras today. Even though human beings are only taking baby steps in fully mimicking the human eye, curiosity and scientific inquiry allows us to discover functions and features of the eye and the visual pathways that will increase our knowledge and help us to build better pixels and image sensor chips.

References

1. Winer, G. A., Cottrell, J. E., Gregg, V., Fournier, J. S., & Bica, L. A., “Fundamentally misunderstanding visual perception: Adults’ beliefs in visual emissions.” American Psychologist, 57, 417-424, 2002.

2. Ertan Salik, “Pinhole Cameras, Imaging, and The Eye” The Fountain Magazine, Issue 54, pp. 30-33, April – June 2006.

3. URL: http://en.wikipedia.org/wiki/Image:Cone-response.png

4. URL: http://www.handprint.com/HP/WCL/color3.html

5. Stefan Winkler, Digital Video Quality – Vision Models and Metrics, John-Wiley & Sons, Ltd., 2005.

6. URL: http://www.clarkvision.com/imagedetail/eye-resolution.html

7. R.C. Gonzalez and R.E. Woods, Digital Image Processing, Addison-Wesley, 1993.

8. M. Schanz, et al., “A high-dynamic-range CMOS image sensor for automotive applications”, IEEE Journal of Solid-State Circuits, vol. 35, no. 7, pp.932-938, July 2000.

In order to get a sharp image, ideally one point on the image (film) should receive light rays from only one point on the object. In practice, this ideal case can not be achieved in case of a large pinhole. If we have a large pinhole, as seen in Fig. 4, the light rays emerging from one point on the object reaches multiple points on the film. Also, multiple points on the object can arrive at a single point on the film. The result of both cases is a blurry image. For a small pinhole, however, there are light rays emerging from a point on the object in all directions, and only a very small amount of light is received on the film. To produce a decent image on the film, the exposure time needs to be very long, especially when a very small pinhole is used. Of course, we can make the pinhole a little larger to capture more light. But, wait! This would make the image blurry. Therefore, for pinhole photography, the size of the pinhole sets the quality of the image and the minimum exposure time. Also, we can take the picture of a still object, but a moving object cannot be captured easily by a pinhole camera due to the long exposure time. One important question is: Can we make reduce the size of the pinhole size to increase the quality of the image? Well, physics says: “No!” Fig. 5 shows a comparison of the images of a filament taken by a pinhole camera.⁶ As the size of the pinhole gets smaller and smaller, the effects of the diffraction phenomenon are more and more pronounced, and the image becomes blurry again. We also notice that the image is barely formed with a very small pinhole, indicating that very little light is received.

How can we gather more light and still make the image sharp? Can we achieve this with just the pinhole? Apparently not. That is why we mention lenses when talking about any imaging system. This is what a lens basically does. A lens gathers more light, and still preserves the one-to-one correspondence between the points on the object and those on the image. So, a lens is very useful for imaging. Most cameras have one or multiple lenses. Our eyes have lenses. We should remember, though, a pinhole camera takes a picture, but the compromise is the exposure time. Now, we see that a lens solves the exposure time problem, but is there a price to pay? To answer this question, let’s take a look at once again Fig. 2, where we see two pictures, one taken by a pinhole camera, and the other one by a lens camera. Look at the pictures carefully, and try to understand the difference before proceeding. As you probably observed, in the pinhole camera image everything in the picture is in sharp focus, from the close-by plants to the far distant beacon, and the clouds in the sky. However, in the lens camera image, only the closest daisy is in focus, and the other daisies, only a few meters away, are blurry. Indeed, we lose the depth of field in our images when using a lens camera. Depth of field can be defined as “The distance between the nearest and farthest points that appear in acceptably sharp focus in an image.” This is actually something we live with everyday. Try to focus your eyes on a mountain far away; the objects that are very close will not be in focus anymore. So, our eyes, consisting of lenses, also have limited depth of field. A nautilus eye, on the other hand, has an infinite depth of field, as it has a pinhole eye. Therefore, the price paid for gathering more light with a lens is that not everything will be in focus.

We can understand why lens cameras have a limited depth of field while a pinhole camera has nearly infinite depth of field if we consider the focusing mechanism of a lens. Given a pre-determined film position, a lens can only form sharp images of an object at a certain distance from the lens. Other points that are farther from or closer than same section of the object will be out of focus. However, if the size of the object is not large, we usually do not notice this effect. When we want to take pictures of close-by objects, then this effect is clearly seen, as Fig. 2 (b) shows.

Actually, we can correct this problem. The image of the farther points of the object forms at a farther point on the film. So, multiple light rays coming from one point will end up on the film. If we place an aperture next to the lens, then we can block some of these light rays. If we make the size of the aperture sufficiently small, we can get a sharp image of the farther point. Our original question about the lenses can be posed once again at this point: By using the aperture we make the image sharper, but what do we lose? Of course, since we block some of the light rays, we lose the light-gathering ability of the lens. Now, if we make the aperture size smaller and smaller, we finally reach the pinhole, and an almost infinite depth of field!

Our eyes also use similar mechanism of placing an aperture. The amount of light allowed to enter each eye is controlled by the iris, a circular diaphragm that opens wide at low light levels and closes to protect the pupil (the aperture) and retina (light detector of the eye) at very high levels of illumination. As illumination changes, the diameter of the pupil (positioned in front of the crystalline lens) reflexively varies between a size of about 2 to 8 millimeters. When illumination is very bright, the pupil narrows and light rays from the side are excluded from the optical pathway.⁷ The result is a sharper image on the retina. A very narrow pupil (approximately 2 millimeters) produces diffraction artifacts that spread the image of a point source on the retina, similar to the image of the filament captured by a very tiny pinhole (Fig. 5)

In conclusion, a pinhole camera is a very instructive tool for learning about imaging concepts. A pinhole camera has an infinite depth of field and the ability to produce sharp images regardless of the distance of the objects. This comes with a price, though: the small size of the pinhole limits the amount of light received by the film, so long exposure times are needed. A lens helps to gather more light, but compromises the depth of field. These concepts are used in imaging technologies, and can be found in the eyes of living organisms.

Notes

1. E. Hecht, Optics, 2nd edition, pp. 199. Addison-Wesley Publishing Co.
2. http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T045986A.gif.
3. http://www.kosara.net/gallery/.
4. http://www.eyedesignbook.com/.
5. http://www.spylife.com/pinholecam.html.
6. http://www.umiacs.umd.edu/~ramani/cmsc426/Lecture3.pdf
7. http://www.olympusmicro.com/primer/lightandcolor/humanvisionintro.html.