Optical zoom typically provides better picture quality than digital zoom on the same camera.
Contrary to what many technical documents on photographic lenses may imply, you don't need an advanced degree in mathematics to understand how lenses work on a digital or film-based camera. Generally, if you have the choice between a digital zoom on a 35 mm digital camera or optical zoom lenses, you will get better results with the optical zoom.
35 mm Cameras
A 35 mm camera refers to the width of the film used, not the lens size. While the film is 35 mm wide, each image is slightly smaller because of the holes required in the film to advance it through the camera sprockets. Each image is 24 mm by 36 mm, giving it a diagonal length of 43.27 mm. Digital cameras marketed as 35 mm approximate the image size of a 35 mm film-based camera, but the actual size depends on the model and manufacturer.
Lens Sizes
A 35 mm lens gets its name from its focal length: the distance from the lens to the film. If the lens' focal length is smaller than the diagonal measurement of the image, you get a wide-angle effect. If the focal length is longer than the image size, it's a zoom effect. A 50 mm lens is often referred to as a "normal" lens, because it's so close to what the human eye sees, but a 35 mm lens creates a wide-angle effect.
Optical Zoom
Professional photographers generally prefer to use an optical zoom, rather than a 35 mm lens with a digital zoom. This is an issue of quality: When an optical zoom lens focuses on an object, it fills the available image size with that object, resulting in almost no degradation of the image, even when you print a large copy of the picture. If you used a digital zoom when taking the picture, trying to crop the image or increase its size on your computer often results in a poor-quality image.
Digital Zoom
Using digital zoom does have some benefits. If you can email pictures directly from your camera, a digital zoom saves you the effort of cropping. Digital zoom also keeps you from having to purchase lenses and change them to take a picture. A high-resolution camera using digital zoom can produce better photos than a low-resolution camera with an optical zoom. You can calculate this by comparing the normal resolution of your camera, then dividing it by the amount of zoom used; for example, an 8 megapixel camera using a 2X digital zoom uses 4 megapixels for the image.
Tags: digital zoom, digital zoom, focal length, image size, optical zoom, camera using