Optical zoom and digital zoom lens pros and cons

Most digital cameras are equipped with a zoom lens as standard. However, some perform with a digital zoom. But how does the optical zoom differ to the digital zoom and what are the pros and cons of these two zoom systems?

What is an Optical Zoom?

 
The old SLR cameras can be used with a range of detachable lenses, adding great flexibility to photography. The digital SLR work in much the same way as the old SLR in that lenses can be detached and changed. This provides the photographer a choice of magnifications from close up to wide angle and therefore could zoom right up to a distant animal and get shots that appeared from just a few feet away. However, the mainstream digital camera, are fitted with a zoom lens that cannot be detached. This meant the photographer was limited to the zoom range it offered.

Ranges of the Optical Zoom Lens

Zoom lens ranges are measured by the number of times the image can be magnified. For instance, a 35mm – 70mm zoom lens has a magnification of X2; a 35mm – 105mm lens has a magnification of X3. The higher the magnification range, the more flexibility the lens offers. All such magnifications are achieved by the optical zoom as the magnification is achieved by a series of specially-curved lenses. The resolution of the image is not affected, as the image is simply viewed by the same principle as peeking through a telescope.

Definition of the Digital Zoom

But in most digital cameras, the digital zoom cuts in at a certain magnification. The digital zoom works merely by cropping the image viewed through the viewfinder to give the impression it has been magnified optically. Digital cameras with a limited zoom capacity (with a magnification range of, say X2) or those with a fixed lens may be fitted with a digital zoom function in order to zoom further by cropping the image and enlarging.

 

Why I don’t Like the Digital Zoom Function

Once the view has reached the maximum optical zoom capacity of the camera’s lens, the camera’s inbuilt digital zoom cuts in. A little bleep might sound, or a marker goes over a point on a bar, displayed on the LCD screen. The image resolution will be degraded from this point on. This is because the digital zoom works in just the same way as cropping an image on the computer’s image software and then enlarging what is left.

Cropping Feature on Digital Zoom

Once the image has been cropped, the total number of pixels left in the image will be reduced. The result? The image resolution will be reduced drastically and the resultant print will appear grainier. Why use the digital zoom when the image can be cropped in the image software anyway?

Why Avoid the Digital Zoom Function

Personally, I would avoid using the digital zoom altogether. I would invest in a digital camera with a more powerful optical zoom (say X5 or more) as can be found in an ultra zoom camera, or a digital SLR which enables the photographer to change the lens. Once I have reached the maximum optical zoom capacity, I will leave it just there and take the shot, even if the object still appears small on the viewing screen. I can then keep a copy of the initial shot and then crop the copy if it contains something interesting not previously noticed. This is better than reducing the image’s resolution by digital zoom.

Cameras with Ultra Zoom and Digital SLRs

The digital zoom does not really zoom into a scene in the same way as the optical zoom. It merely crops the image and then enlarges it so that it fits the LCD screen. This will cause the image to lose resolution and appear grainier when it is printed. If image quality is paramount in photos, I would invest in a digital camera with an ultra zoom lens or a digital SLR. A digital zoom is to be avoided if possible.

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