How is optical zoom different from digital zoom?

The optical zoom of digital cameras functions in the same way as the one on normal 35 mm cameras. The lens moves forward and backwards to bring the image closer without losing any quality. The optical magnification of the moving lenses ranges from 2.0x to 10.0x. The closer you get to the upper end, the farther away the subject can be when you take a photo. On the other hand, digital zoom is actually a software that simulates optical zoom without any physical movement. What it does is to crop the picture and enlarge it, just like a photo editing application which you can use afterwards. Using an image editor after having transferred the photos to your computer is actually a better option because you have higher control over what you crop. Some newer digital camera models automatically switch to digital zoom when you have exceeded the capacity of the optical zoom. If you don't want this to happen you can switch the feature off.

What zooming capacity should a digital camera have form optimal performance?

As stated earlier, optical zoom can range from 2x to 10x, but the majority of users are satisfied with 3x-6x. However, a high zooming capacity is a good thing, as long as you make sure you don't overlook other features.

What is a megapixel?

A megapixel consists of a million pixels. 'Pixel' is the short term for 'picture element' , which is one of the millions of little spots that make digital images. Your PC screen and digital camera images are made out of grids of such dots. Each of them holds a color and all these colors dots combined form the picture. To find out the total number of pixels, multiply the vertical by the horizontal dimension. The average PC screen, for example, has 1024 x 768 = 786,432 pixels or 0.8 megapixels. A camera with a higher number of megapixels can take more detailed and clear photos. For example, if you take a photo with a 2 megapixel camera, you will get two million pixels, while with a 4 megapixel one you get 4 million pixels. If you only print them in small sizes you will probably not see any difference, but on 8x10 prints it shows.

How many pixels do I need?

It depends on what you want to do with your photos. If you don't usually crop them and only print in small sizes (4x6, 5x7), you can do great with a 2-3 MP camera. In case you want to print photos in larger sizes, you need at least 4 MP. Despite the numerous advices you might receive to get the highest resolution camera you can afford, you should think of what you need and the fact that there are other features to consider too.

How is a nickel-cadmium (Ni-Cd) battery different from a nickel-metal hydride (NiMH) one?

Ni-Cd and NiMH batteries look pretty much the same, but NiMH batteries use hydrogen absorbing alloy instead of cadmium. A NiMH battery has 2-3 times higher capacity compared to a Ni-Cd one of approximately the same size and has lower environmental impact.