Explain , optical and digital zoom, that are used in digital cameras.?

Optical zoom uses the optics (lens) of the camera to bring the subject closer. Digital zoom is an invention of digital video cameras. It is not uncommon to see digital videocams with 300x digital zoom.

For our purpose, digital zoom is not really zoom, in the strictest definition of the term. What digital zoom does is enlarge a portion of the image, thus 'simulating' optical zoom. In other words, the camera crops a portion of the image and then enlarges it back to size. In so doing, you lose image quality. If you've been regularly using digital zoom and wondered why your pictures did not look that great, now you know.

With optical zoom, the lens zooms in and out. This is very useful.
Digital zoom is a gimmick, where the camera crops the picture in-camera.

Just push the big red button.

optical zoom uses an actual lens, either plastic or glass, to focus and zoom in on an object. This will actually make image come in closer by magnification.

Digital zoom takes the captured image and enlarges it. That is why it can become pixelated. The same happens when you try to enlarge a jpg, the bigger it gets the fuzzier and more pixelated it becomes.

Good tutorials are available at

http://www.kodak.com/eknec/PageQuerier.j...
http://www.photoxels.com/article-optical...

optical zoom is a glass lense that bring faraway objects up close without loosing clarity.digital zoom looses clarity because you have less pixels.