An Extended Optical Zoom enables the zoom ratio of a digital camera to extended beyond the maximum length of the optical zoom. There is little if any loss of image quality like when using a digital zoom.
A digital zoom crops an image in camera. An Extended Optical Zoom trims the operational area of the actual camera sensor to increase the maximum magnification.
The Extended Optical Zoom has been compared to using an add-on converter lens. However, a converter lens reduces the size of the camera aperture size and results in a slower shutter speed. An Extended Optical Zoom does not.
Greater zoom range, smaller image size
Extended Optical Zooms work when a smaller image size is selected than the largest size available on a digital camera. For example, on a seven megapixel camera, a resolution of less than seven megapixels must be used. A 10X seven megapixel digital camera, such as the Panasonic TZ3, can extend the optical zoom up to 15X, depending on the selected resolution.
Before using an Extended Optical Zoom, determine if the gain in zoom power is worth the reduced image size.
Extended Optical Zoom is also known under other names such as Smart Zoom, Extra Optical Zoom and Safety Zoom.