Creates a gallery of all the attached images to a page or post, with an inner zoom to the full image.
Check the dimensions of the original image and the dimensions set in Settings > Media. Your original image should be larger than the dimensions set for the large (or your preferred size) image in the Media settingspage.
If you have a text in the captions area of your image in the Media Library, it is shown on the picture. The text disappears on mouseover. If you don't want the captions to be shown but don't want to delete them, use a display: none; in your stylesheet. You can change the style of the captions by overriding the css in your own stylesheet.
[sabineszoom showsize=medium] if you want the medium size or
[sabineszoom showsize=thumbnail] for the thumbnail