Product Image Zoom is enabled by default. To deactivate or re-activate this feature, follow these steps:
In your Admin Area, go to Inventory > Products.
Click the three-dot actions menu icon and select All Products Settings.
Select or deselect Enable Image Zoom.
When enabled, the product image is magnified when the cursor is moved across it. This feature also works for the additional product photos if the product is equipped with alternate views.
Photo Size Requirements for Image Zoom
Note that for this feature to work, a product's High Resolution Zoom Image (large) must be at least 300 pixels wide or 300 pixels high and must be 20% larger than the Displayed on Product Page (medium) image.
The default size of your main product photo, Displayed on Product Page (medium), is 400px. If you leave the medium image at this default size, the High Resolution Zoom Image (large) needs to be 480px or greater in order to trigger the image zoom feature (480px is exactly 20% larger than 400px). However, if you use the Advanced Settings to increase the medium image size from the default value, your large image size will need to be greater than 480px as a result.
The default size for the High Resolution Zoom Image (large) is 1200px, which is 300% of the default medium image and more than satisfies the requirements for triggering the zoom features. However, if the image you upload is smaller than 1200px, the system cannot generate a zoom image any larger than the original photo size. Therefore, if you want the large image size to remain 1200px, the image you upload needs to be at least 1200px itself.
To calculate the minimum photo size necessary to trigger the image zoom feature, multiply the largest dimension of your Displayed on Product Page (medium) image by 1.2. For example, if you increase the maximum dimension of your medium photo to 500px, your High Resolution Zoom Image (large) image must be at least 600px (500 x 1.2 = 600).
For more information on default image sizes, see Product Images.