Sunday, April 22, 2018

Digital or Optical zoom for Security Cameras

Digital or Optical zoom for Security Cameras

When shopping for security dome cameras with zoom capabilities, the question I ask myself is which is more important; digital or optical zoom?  When speaking of surveillance cameras you want to get “close” to a subject from a fixed camera position. The zoom control on your digital camera will let you get “close” enough to capture that bigger image. It will also let you zoom out to include a wide angle of view. 

What is optical zoom?
Optical zoom is a true zoom lens, which is physically extend to magnify your subject. A motor controls the lens movement. 

What is digital zoom?
Digital zoom is simply some in-camera image processing, basically decreasing the apparent angle of view of a digital photographic or video image. To make the cropped area bigger, digital zoom makes up, or interpolates, pixels to add to the image, which may give less than satisfactory results.

Zoom meaning the ability to make something distant appear closer. Basically it’s a ratio of the longest and shortest focal length.
A 17mm (Wide) to 50mm (Tele) lens would be roughly 3x zoom. (50/17 = 2.94)
However a 70mm (Wide) - 200mm (Tele) lens would also be a roughly 3x zoom. (200/70 = 2.86) 

Summary:
1. Optical zoom uses lenses to zoom in on the image before the sensor captures it.
2. Digital zoom uses the processor to magnify the image after the sensor captures it.
3. Optical zoom preserves the crispness and detail of the image while digital zoom tends to interpolate a lot of the data.
4. Cameras with optical zoom are generally more expensive and bigger than cameras that only have digital zoom.
5. Constant adjusting of the zoom level in a camera with optical zoom might drain the battery a little bit faster.


9 comments:

Anonymous said...

good post. Sir What about optical zoom vs. resolution ?

Stephen Otra said...

Realizing that digital zoom is not really a good thing because it negatively affects image quality, camera manufacturers have introduced a new type of digital zoom variously called “Smart Zoom” (Sony), “Safe Zoom” (Canon) and “Intelligent Zoom” (Panasonic and others). Smart/Safe/Intelligent Zoom (let’s collectively called them Intelligent Zoom, or iZoom for short) can be viewed as an “ethical” digital zoom which avoids interpolating the image and so avoid degrading image quality. iZoom works only if you select an image size smaller than the full available image size. So, for example, if your digital camera is capable of producing a 12MP image, Smart Zoom is available only if you select to save your images as 7MP or less. In other words, with this particular type of digital zoom, the MP resolution decreases as you ‘zoom’ — in other words you are just cropping the center of the image (without enlarging and interpolating back to the original resolution).

iZoom Systems said...

I call iZoom “ethical digital zoom” because it is not made available at full image size — this would cause image degradation. The smaller you elect to save your image, the more iZoom power you have available (folks, you’re basically just cropping the image without re-enlarging, which you can also do at any time in post-processing).

So, our recommendation still holds. If you want zoom power, only optical zoom matters! iZoom is the better form of digital zoom, but what you gain in simulated zoom power (again, you’re just cropping), you lose in image size. There’s no free lunch.

Bronwyn said...

Another advantage of digital zoom:

I take pictures of birds and I have found that autofocus fails in a lot of situations especially when the subject is small in the frame. (I use autofocus because I often only have 2 or 3 seconds to get the shot before the bird flies away.) But if I increase the zoom into the digital range, so that the subject fills more of the frame, the autofocus works better. The net result is that I now almost always zoom out to the max optical + digital and end up with better pictures of birds, because a grainy in-focus shot is better than an out-of-focus hi-res shot.

So if your subject is small in the frame, I would strongly recommend using max digital zoom to increase your chances of getting an in-focus shot.

Perhaps the focusing technology will someday improve where I can select a pinpoint and it will get lock on to it. But for right now its not there.

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