Product images
The sizes generated for product photography. When you upload a product image, the store creates the versions it needs from it, such as the large image on a product page and the smaller one in a listing.
Generating sized versions is what keeps the storefront fast. A shopper browsing a listing page loads small images rather than full-size photography.
How to Configure Product Image Sizes
Select the store you would like to update
Click on Manage Store Settings underneath Settings
Open Image Sizes
Open the Product images section
Set the sizes you want generated
Save your changes
Changing these sizes affects images generated from that point on. Images already uploaded keep the sizes they were generated with, so you may need to re-upload affected products to see the change everywhere.