When zooming in on an image with a digital camera, which zoom type maintains high image quality?

Optical zoom is the correct choice because it uses the camera's lens to magnify the subject while maintaining the image quality. This is achieved through the physical movement of the lens elements, allowing for a closer view of the subject without losing resolution. As the zoom is achieved through optics rather than software manipulation, the details and clarity of the image remain sharp and well-defined.

In contrast, digital zoom enlarges an image by cropping it and then scaling it back up to the original size digitally, which can lead to a loss of detail and a pixelated appearance. Crop zoom is essentially another interpretation of digital zoom, as it involves taking a portion of the image and enlarging it, which again impacts image quality. Instant zoom is not a widely recognized term in photography and does not pertain directly to the mechanics of zooming, further emphasizing that optical zoom is the superior choice for maintaining quality.