Don't want resize of the image ,want to implement magic zoom

Hi

We would like to implement magic zoom ,for which big size image is required ,but when we upload the image of a product size is always reduced ,however big image we try to upload ,we think that the upload control is resizing the image ,how can we stop it from resizing

Please help

you can control the product image sizes by going to admin

configuration-->global settings

click the 'media' tab


-hayden