Before I go and Explain Optical And Digital Zoom, you must understand that a digital image is a composition of pixels.
Your computer monitor screen, just like your television screen, consists of tiny pixels. When you purchase a LCD screen you must heard of resolutions like 800 x 600, 1024 x 768, etc. Those represents the number of pixels across horizontally and vertically on the screen. Same thing with digial cameras where they specify the resolution of the digital images that they take. For example, cameras that take 4 megapixels, or even 8 megapixels are common place nowadays.
Now, let’s look at an example of a digital image below:
This was a picture that I took with my Canon 20D that I purchased from Amazon. Let’s talk about digital zoom first. Digital zoom is no more than exploding an existing digital image. If you look at the moon image above, I have digitally zoomed 4 times into a fire ant. As you can see, the original fire ant in the picture is very sharp and well defined. But after I applied the digital zoom into a fire ant, that 4x digital zoomed fire ant becomes very blurred.
Essentially when you zoom digitally by 4 times, you are doing no more than just splitting an existing pixel into 4 pixels. As you can imagine, it will cause some information to be lost when you are splitting one pixel into 4 pixels. What should the computer do with the extra pixels that it is creating? There are many algorithms of digial zooms that will “smoothen” the effect of digial zooming, and that is a study by itself.
Now, optical zoom is a different story. In the digital world, a digital image’s “sharpness” is limited by the resolution of your camera, for example 8 megapixels represents the maximum resolution that this image will contain. If you want to digital zoom this image to 16 megapixels, or even 32 megapixels, the information is simply not there. In the optical world, the optical zoom allows your camera to zoom into the subject and capture that same 8 megapixels of information. Practically speaking, optical zoom allows that same 8 megapixels of information to be taken at a closer “look.” Think of it like a magnifying glass. For example, the same image above is taken at a optical zoom of 4x on the same fire ant. See below:
As you can see the same fire ant is much more clear.
Very quickly, I want to comment on my Canon 20D digital camera. It is an excellent camera. Now, it is not a point and shoot camera and it is used by many professional photographers and hobbysts alike. Check it out at Amazon: