Human eye operates by scanning a complete scene in their field of
vision, correcting the focus automatically at ever point. The image
seen by the eyes is sent to the brain to do the instantaneous focus
correction. Human eye function instantaneously, it monitors and adjust
the focus constantly and responding to very subtle changes in the
volume of light present.
There is however a slight time lag for camera, even a DSLR with really
good autofocus system will usually takes some time for the autofocus
mechanism to be complete. And we would still have to decide on the
point of focus.
Human eye operates at relative constant speed of roughly around 1/60
second whereas a lot of cameras can go a lot faster than that. Most
DSLR could go up to 1/8000 or even faster. Of course, what we see at
1/60 second is not going to be the same as what is captured by camera
at 1/8000 second. All motion that could be seen at 1/60 second would
appear arrested at 1/8000 second. In a way, camera see things in a way
that human eye physically could not see.
Human eye can see everything that is eight inches outwards sharply.
Farther away, every object within the range of vision will still appear
sharply focus. In other words, human eyes has virtually unlimited depth
Camera however is not so flexible in displaying wide range of sharply
focus image. The depth of field of camera is restricted by the focal
length of the camera lens, distance of the subject to the camera,
aperture of the camera lens, etc. Try using a 50mm camera lens on a
full frame 35mm camera, f/8 aperture size to focus on subjects that is
10 feet away and you will find that only objects that is one foot in
front and behind the subject that is sharply focused. Of course, many
photographers strive for very shallow depth of field as the rightly
focused subject would appear stand out compare to the surrounding
objects that is blurred.
Our brain interprets what our eyes see and translate into true 3-D
images with unlimited depth of view. Camera’s depth of field is however
limited and controlled by the aperture size of the camera lens,
distance of the subject from the camera and focal length of the camera
Human eyes are capable of seeing a greater range of tones from dark to
bright condition, as human eyes has a contrast range of 1000:1 or even
Camera on the other hand depends on the sensor or the film which
usually has the contrast range of 100:1. Thus, we need to be aware that
what we can see with our human eye is not what we can get with our
camera, a lot of details in the dark or bright places would not be
captured when taken together.
Angle of View
Human eye has a very limited visual view of around 20 degrees, which
cover 10 degrees on each side of the optical view. This is where human
eye can see very fine details and focus correctly. Of course there is
also the peripheral vision which would provide us with almost 180
degree of vision, but with peripheral vision, the image seen would not
be accurate and could not be identify correctly. Peripheral vision
basically just to allow us to “sense” objects in a wider vision view.
For camera, the angle of view is fixed and decided by the focal length
of the camera lenses and the camera format. A 50mm lens on a full frame
35mm format camera would encompasses around 46 degree whereas a 25mm
lens on the 35mm format camera would encompass around 84 degrees. Zoom
lens would cover a wide range of angle of view but it would still be
one at a time and the zooming effects is done manually compare to the
automation of human eye.
Our brain interprets what we see from our eyes; it translates the color
of the subject and let us knows what the right color is. Our brain also
does correction under different lighting environment so that things
like skin tones would appear normal even when under extreme lighting
environment. Normally we would be able to see seven distinct color
involving red, blue, yellow, green, white, black and gray. Although,
there are people that is color blind and might not be able to see
Camera however, usually has its own color bias, depending on model.
Different model of camera has its own setting of color bias, some are
slightly yellowish, some are predominate in blues, greens, etc. Camera
lenses also have some effect on color rendition as different models of
camera lens would detect different color rendition. That’s the reason
why that a same scenes captured with different camera and camera lens
will appear different, especially in color.