After reading the title of this article, you might be asking
yourself, “Zooming is just zooming, right?” Is there really a difference
between optical and digital zooming? You may be surprised to learn that
yes, there is definitely a difference.
Optical zoom is considered as true zooming. In other
words, the lens optics on the camera itself are used to zoom in on an
object. This is opposed to digital zooming, in which the camera processes
an image internally and focuses on a certain portion of that image. That
certain portion is simply enlarged, thus creating a zoom effect.
One such term is zoom.
Pan-tilt-zoom (PTZ) cameras and some fixed cameras have lenses that zoom
in on an object. In other words, it magnifies the object of the video,
such as a car in a parking lot, so that it can be seen in much better detail.
Zoom is a very important feature of video camera lenses.
By making the image larger, it is possible to watch intrusions developing
from some distance away from the doors to a building.
In a secure parking lot, for example, if someone bypasses
the guard shack, a zoom camera mounted on the side of a building over a hundred
feet away should be able to capture easily the progression of the automobile as
it gets closer to the building. This gives time for a security guard to
respond before the intruder is leaning over his shoulder with a gun pointed to
his head.
This may seem to be an extreme example, but it is one of the
things that separates zoom cameras from fixed ones.
When comparing the zoom features of a camera lens, it is
absolutely critical to understand the difference between digital zoom and optical zoom.
Digital Zoom
Imagine that you are looking at a Rembrandt in a museum, and
you want to get closer to a beautiful pastoral scene to see the master’s
details of a country hillside.
Since the guard is paying attention, you have to settle for
taking a regular picture of the Rembrandt from a safe distance away.
Then, you have the picture developed and you now hold in your hand the
photo you took at the museum.
You have an idea. Now that you have the picture in
hand, you decide to get someone to blow up the picture on a copier so that you
can see the hillside better. At least, that’s what you think you’re going
to get.
When you blow the picture up to the same size of the full
original painting, you are disappointed. Now, it just looks like a bad
case of psoriasis and you have missed an opportunity to bring Rembrandt home
with you.
Digital zoom is very similar to this. It cuts out a section
on a distant image, not actually getting you closer to the object but by
magnifying the lack of clarity that already exists. In other words, if
you can’t tell what the details are from a distance, you won’t be able to tell
what they are by making it seem closer by digitally manipulating the captured
picture.
Digital zoom, while not exactly useless, does not actually
help very much when you need to focus on an object as if you are standing much
closer to it.
Put yourself back in the art museum for a moment. You
are standing in front of the Rembrandt and you really want to get closer to it
so you can see the finer details of the hillside. This time, you don’t
have a camera. Instead, the sleepy-faced guard has his head turned, and
you jump over the barriers and put your eyes about six inches away from the
painting.
Suddenly, all the details of the hillside are shown.
You see the individual blades of grass, the lines on the outer edges
which distinguish an object from its background. You can see it clearly,
and your awe of Rembrandt grows to new heights.
Optical zoom is like standing closer to the object.
In our opening example about the car crashing the guard
shack, it would be as if the security guard is only a few feet away from the
automobile, allowing him to head off the intruder before he reaches the front
door.
The value of optical zoom in video surveillance is
priceless. While it is not quite as good as you will see on television
cop shows, it is still a great tool for keeping an eye on your property.
