Friday, September 25, 2015

Human Eye ... a 576MP marvel .... but u need only 7 :)

Today i came across a very interesting video about a camera lenses which is compared with Human vision. Human Eye ..... A medical marvel ..... only God/ALLAH can create. Ask any medical students/Doctors how difficult an eye internal structure is. 

I am sure many of you have came across a post which says that human eye resolution is 576 mega pixels .... Right! Ever wonder how this number came up? It was calculated based many factor which you will find on below link. 

The eye is not a single frame snapshot camera. It is more like a video stream. The eye moves rapidly in small angular amounts and continually updates the image in one's brain to "paint" the detail. We also have two eyes, and our brains combine the signals to increase the resolution further. We also typically move our eyes around the scene to gather more information. Because of these factors, the eye plus brain assembles a higher resolution image than possible with the number of photoreceptors in the retina. So the megapixel equivalent numbers above refer to the spatial detail in an image that would be required to show what the human eye could see when you view a scene.

But here is a surprise ..... out of those so called 576 Mega Pixels, we need only 7 Mega Pixels to view any thing/scene or stare in general .... & besides that one stare we need only 1 Mega Pixel to view the surrounding which mostly ignore by our brain including nose and glasses that are coming in our vision but our brain ignores it. Cannot believe it? .... Close your one eye & see.  Check out below link for a very interesting video explaining much more on this. 

Ok ..... Enough with the resolution. Now lets talk about focal length which caused me to writing this blog. 

If we try to replicate our eye focal length range into one lens, it is impossible at this point in time. May be in future any technology advancement can do that .... just may be. Our eye can see as wide as 150 degree which is equivalent to 5mm super ultra wide angle lens .... to .... recognising the small letters in book which is nearly 1 degree equivalent to 2500mm super ultra telephoto lens. So you getting the extreme dimension here .... from 5mm <----> 2500mm ..... all variation of these focal length is happening inside our eye. Now thats a medical marvel. I doubt i able to see any such lens at least not in my lifetime which can vary to these extreme values (in a single housing). Adding further, then we try to focus on a letter or a face, the 1 degree view kicks in (with 7 mega pixel resolution of course) and image made on "Fovea" which is a pitfall over a Retina inside of our eye ball .... a very tiny spot which is made of hundreds of thousands of optical nerves and other stuff (medical student s/Doctors knows what i am talking here). 

On the other hand, if we are standing still and trying to move around our eyes we can see almost 150 degree of view (equivalent of 5mm lens) which makes 576 MP of "snap shot" (in theory) but our eyes are capturing not a snap shot, they are constantly streaming live video stream  as mentioned above at many frames per seconds using 2 streams (2 eyes) and BRAIN process them one by eliminating unnecessary stuff like nose and glasses and this happening 24x7x365xYour total life. Even right now you are reading this line using 7MP of your eyes resolution and almost 2500mm of equivalent of focal length "Settings" inside of your eyes .... ignoring the rest of the screen  & world (or shall i say ignoring the rest of the 569 MP of your eye) of your laptop/computer/mobile. 

In last, there is a "general setting" of our eye which is called central retina which is equivalent of 38mm (50 degree) . Note that this focal length is vary from person to person ..... say from 28mm ~ 40mm. But in general its scaled mean value to 38mm. This is something you are viewing any thing in general or sitting in the cinema and trying to get back row seat to get complete view of the screen ..... rather then sitting in the front row and constantly move your head left to right trying to grab the movie. This focal length is basically derives the famous 35mm focal length on which almost all of the world MOBILE CAMERA are calibrated. Thats why all photo journalist prefer to work with 35mm focal length prime lens because it gives more of realistic view of any normal human vision as what we see & how we see the world. In short ..... 35mm focal length is the most used focal length in human history. 

Actually below image caused me writing this blog which was from a paid workshop over Nikon lenses from famous photographer John Greengo. Later i did some google and added couple of links above to add additional human eye mega pixel flavour to make something interesting & some additional info for learning purpose. 

Now just think for a second .... how much powerful human eye is. How the mighty one created something that we as a human is yet to discover and understands many hidden feature of human body. 

Till next time ..... Happy Learning Guys !

Babar Swaleheen
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